thirdparty: use CLI11 v2.4.1

1 files changed, 1611 insertions, 331 deletions

diff --git a/thirdparty/CLI11.hpp b/thirdparty/CLI11.hpp
index 3913fa9..41027f0 100644
--- a/thirdparty/CLI11.hpp
+++ b/thirdparty/CLI11.hpp
@@ -1,11 +1,11 @@
-// CLI11: Version 2.3.2
+// CLI11: Version 2.4.1
 // Originally designed by Henry Schreiner
 // https://github.com/CLIUtils/CLI11
 //
 // This is a standalone header file generated by MakeSingleHeader.py in CLI11/scripts
-// from: v2.3.2
+// from: v2.4.1
 //
-// CLI11 2.3.2 Copyright (c) 2017-2022 University of Cincinnati, developed by Henry
+// CLI11 2.4.1 Copyright (c) 2017-2024 University of Cincinnati, developed by Henry
 // Schreiner under NSF AWARD 1414736. All rights reserved.
 //
 // Redistribution and use in source and binary forms of CLI11, with or without
@@ -34,34 +34,40 @@
 #pragma once
 
 // Standard combined includes:
-#include <iomanip>
-#include <set>
-#include <memory>
-#include <vector>
-#include <utility>
-#include <stdexcept>
-#include <locale>
+#include <algorithm>
+#include <array>
+#include <cctype>
+#include <clocale>
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <cwchar>
+#include <exception>
+#include <fstream>
 #include <functional>
+#include <iomanip>
 #include <iostream>
 #include <iterator>
-#include <exception>
+#include <limits>
+#include <locale>
+#include <map>
+#include <memory>
 #include <numeric>
-#include <fstream>
+#include <set>
+#include <sstream>
+#include <stdexcept>
 #include <string>
-#include <type_traits>
 #include <tuple>
-#include <map>
-#include <algorithm>
-#include <cstdint>
-#include <sstream>
-#include <cmath>
-#include <limits>
+#include <type_traits>
+#include <utility>
+#include <vector>
 
 
 #define CLI11_VERSION_MAJOR 2
-#define CLI11_VERSION_MINOR 3
-#define CLI11_VERSION_PATCH 2
-#define CLI11_VERSION "2.3.2"
+#define CLI11_VERSION_MINOR 4
+#define CLI11_VERSION_PATCH 1
+#define CLI11_VERSION "2.4.1"
 
 
 
@@ -124,17 +130,7 @@
 #endif
 #endif
 
-/** Inline macro **/
-#ifdef CLI11_COMPILE
-#define CLI11_INLINE
-#else
-#define CLI11_INLINE inline
-#endif
-
-
-
-// C standard library
-// Only needed for existence checking
+/** <filesystem> availability */
 #if defined CLI11_CPP17 && defined __has_include && !defined CLI11_HAS_FILESYSTEM
 #if __has_include(<filesystem>)
 // Filesystem cannot be used if targeting macOS < 10.15
@@ -161,6 +157,44 @@
 #endif
 #endif
 
+/** <codecvt> availability */
+#if defined(__GNUC__) && !defined(__llvm__) && !defined(__INTEL_COMPILER) && __GNUC__ < 5
+#define CLI11_HAS_CODECVT 0
+#else
+#define CLI11_HAS_CODECVT 1
+#include <codecvt>
+#endif
+
+/** disable deprecations */
+#if defined(__GNUC__)  // GCC or clang
+#define CLI11_DIAGNOSTIC_PUSH _Pragma("GCC diagnostic push")
+#define CLI11_DIAGNOSTIC_POP _Pragma("GCC diagnostic pop")
+
+#define CLI11_DIAGNOSTIC_IGNORE_DEPRECATED _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"")
+
+#elif defined(_MSC_VER)
+#define CLI11_DIAGNOSTIC_PUSH __pragma(warning(push))
+#define CLI11_DIAGNOSTIC_POP __pragma(warning(pop))
+
+#define CLI11_DIAGNOSTIC_IGNORE_DEPRECATED __pragma(warning(disable : 4996))
+
+#else
+#define CLI11_DIAGNOSTIC_PUSH
+#define CLI11_DIAGNOSTIC_POP
+
+#define CLI11_DIAGNOSTIC_IGNORE_DEPRECATED
+
+#endif
+
+/** Inline macro **/
+#ifdef CLI11_COMPILE
+#define CLI11_INLINE
+#else
+#define CLI11_INLINE inline
+#endif
+
+
+
 #if defined CLI11_HAS_FILESYSTEM && CLI11_HAS_FILESYSTEM > 0
 #include <filesystem>  // NOLINT(build/include)
 #else
@@ -170,9 +204,244 @@
 
 
 
+
+#ifdef CLI11_CPP17
+#include <string_view>
+#endif  // CLI11_CPP17
+
+#if defined CLI11_HAS_FILESYSTEM && CLI11_HAS_FILESYSTEM > 0
+#include <filesystem>
+#include <string_view>  // NOLINT(build/include)
+#endif                  // CLI11_HAS_FILESYSTEM
+
+
+
+#if defined(_WIN32)
+#if !(defined(_AMD64_) || defined(_X86_) || defined(_ARM_))
+#if defined(__amd64__) || defined(__amd64) || defined(__x86_64__) || defined(__x86_64) || defined(_M_X64) ||           \
+    defined(_M_AMD64)
+#define _AMD64_
+#elif defined(i386) || defined(__i386) || defined(__i386__) || defined(__i386__) || defined(_M_IX86)
+#define _X86_
+#elif defined(__arm__) || defined(_M_ARM) || defined(_M_ARMT)
+#define _ARM_
+#elif defined(__aarch64__) || defined(_M_ARM64)
+#define _ARM64_
+#elif defined(_M_ARM64EC)
+#define _ARM64EC_
+#endif
+#endif
+
+// first
+#ifndef NOMINMAX
+// if NOMINMAX is already defined we don't want to mess with that either way
+#define NOMINMAX
+#include <windef.h>
+#undef NOMINMAX
+#else
+#include <windef.h>
+#endif
+
+// second
+#include <winbase.h>
+// third
+#include <processthreadsapi.h>
+#include <shellapi.h>
+#endif
+
+
 namespace CLI {
 
 
+/// Convert a wide string to a narrow string.
+CLI11_INLINE std::string narrow(const std::wstring &str);
+CLI11_INLINE std::string narrow(const wchar_t *str);
+CLI11_INLINE std::string narrow(const wchar_t *str, std::size_t size);
+
+/// Convert a narrow string to a wide string.
+CLI11_INLINE std::wstring widen(const std::string &str);
+CLI11_INLINE std::wstring widen(const char *str);
+CLI11_INLINE std::wstring widen(const char *str, std::size_t size);
+
+#ifdef CLI11_CPP17
+CLI11_INLINE std::string narrow(std::wstring_view str);
+CLI11_INLINE std::wstring widen(std::string_view str);
+#endif  // CLI11_CPP17
+
+#if defined CLI11_HAS_FILESYSTEM && CLI11_HAS_FILESYSTEM > 0
+/// Convert a char-string to a native path correctly.
+CLI11_INLINE std::filesystem::path to_path(std::string_view str);
+#endif  // CLI11_HAS_FILESYSTEM
+
+
+
+
+namespace detail {
+
+#if !CLI11_HAS_CODECVT
+/// Attempt to set one of the acceptable unicode locales for conversion
+CLI11_INLINE void set_unicode_locale() {
+    static const std::array<const char *, 3> unicode_locales{{"C.UTF-8", "en_US.UTF-8", ".UTF-8"}};
+
+    for(const auto &locale_name : unicode_locales) {
+        if(std::setlocale(LC_ALL, locale_name) != nullptr) {
+            return;
+        }
+    }
+    throw std::runtime_error("CLI::narrow: could not set locale to C.UTF-8");
+}
+
+template <typename F> struct scope_guard_t {
+    F closure;
+
+    explicit scope_guard_t(F closure_) : closure(closure_) {}
+    ~scope_guard_t() { closure(); }
+};
+
+template <typename F> CLI11_NODISCARD CLI11_INLINE scope_guard_t<F> scope_guard(F &&closure) {
+    return scope_guard_t<F>{std::forward<F>(closure)};
+}
+
+#endif  // !CLI11_HAS_CODECVT
+
+CLI11_DIAGNOSTIC_PUSH
+CLI11_DIAGNOSTIC_IGNORE_DEPRECATED
+
+CLI11_INLINE std::string narrow_impl(const wchar_t *str, std::size_t str_size) {
+#if CLI11_HAS_CODECVT
+#ifdef _WIN32
+    return std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>>().to_bytes(str, str + str_size);
+
+#else
+    return std::wstring_convert<std::codecvt_utf8<wchar_t>>().to_bytes(str, str + str_size);
+
+#endif  // _WIN32
+#else   // CLI11_HAS_CODECVT
+    (void)str_size;
+    std::mbstate_t state = std::mbstate_t();
+    const wchar_t *it = str;
+
+    std::string old_locale = std::setlocale(LC_ALL, nullptr);
+    auto sg = scope_guard([&] { std::setlocale(LC_ALL, old_locale.c_str()); });
+    set_unicode_locale();
+
+    std::size_t new_size = std::wcsrtombs(nullptr, &it, 0, &state);
+    if(new_size == static_cast<std::size_t>(-1)) {
+        throw std::runtime_error("CLI::narrow: conversion error in std::wcsrtombs at offset " +
+                                 std::to_string(it - str));
+    }
+    std::string result(new_size, '\0');
+    std::wcsrtombs(const_cast<char *>(result.data()), &str, new_size, &state);
+
+    return result;
+
+#endif  // CLI11_HAS_CODECVT
+}
+
+CLI11_INLINE std::wstring widen_impl(const char *str, std::size_t str_size) {
+#if CLI11_HAS_CODECVT
+#ifdef _WIN32
+    return std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>>().from_bytes(str, str + str_size);
+
+#else
+    return std::wstring_convert<std::codecvt_utf8<wchar_t>>().from_bytes(str, str + str_size);
+
+#endif  // _WIN32
+#else   // CLI11_HAS_CODECVT
+    (void)str_size;
+    std::mbstate_t state = std::mbstate_t();
+    const char *it = str;
+
+    std::string old_locale = std::setlocale(LC_ALL, nullptr);
+    auto sg = scope_guard([&] { std::setlocale(LC_ALL, old_locale.c_str()); });
+    set_unicode_locale();
+
+    std::size_t new_size = std::mbsrtowcs(nullptr, &it, 0, &state);
+    if(new_size == static_cast<std::size_t>(-1)) {
+        throw std::runtime_error("CLI::widen: conversion error in std::mbsrtowcs at offset " +
+                                 std::to_string(it - str));
+    }
+    std::wstring result(new_size, L'\0');
+    std::mbsrtowcs(const_cast<wchar_t *>(result.data()), &str, new_size, &state);
+
+    return result;
+
+#endif  // CLI11_HAS_CODECVT
+}
+
+CLI11_DIAGNOSTIC_POP
+
+}  // namespace detail
+
+CLI11_INLINE std::string narrow(const wchar_t *str, std::size_t str_size) { return detail::narrow_impl(str, str_size); }
+CLI11_INLINE std::string narrow(const std::wstring &str) { return detail::narrow_impl(str.data(), str.size()); }
+// Flawfinder: ignore
+CLI11_INLINE std::string narrow(const wchar_t *str) { return detail::narrow_impl(str, std::wcslen(str)); }
+
+CLI11_INLINE std::wstring widen(const char *str, std::size_t str_size) { return detail::widen_impl(str, str_size); }
+CLI11_INLINE std::wstring widen(const std::string &str) { return detail::widen_impl(str.data(), str.size()); }
+// Flawfinder: ignore
+CLI11_INLINE std::wstring widen(const char *str) { return detail::widen_impl(str, std::strlen(str)); }
+
+#ifdef CLI11_CPP17
+CLI11_INLINE std::string narrow(std::wstring_view str) { return detail::narrow_impl(str.data(), str.size()); }
+CLI11_INLINE std::wstring widen(std::string_view str) { return detail::widen_impl(str.data(), str.size()); }
+#endif  // CLI11_CPP17
+
+#if defined CLI11_HAS_FILESYSTEM && CLI11_HAS_FILESYSTEM > 0
+CLI11_INLINE std::filesystem::path to_path(std::string_view str) {
+    return std::filesystem::path{
+#ifdef _WIN32
+        widen(str)
+#else
+        str
+#endif  // _WIN32
+    };
+}
+#endif  // CLI11_HAS_FILESYSTEM
+
+
+
+
+namespace detail {
+#ifdef _WIN32
+/// Decode and return UTF-8 argv from GetCommandLineW.
+CLI11_INLINE std::vector<std::string> compute_win32_argv();
+#endif
+}  // namespace detail
+
+
+
+namespace detail {
+
+#ifdef _WIN32
+CLI11_INLINE std::vector<std::string> compute_win32_argv() {
+    std::vector<std::string> result;
+    int argc = 0;
+
+    auto deleter = [](wchar_t **ptr) { LocalFree(ptr); };
+    // NOLINTBEGIN(*-avoid-c-arrays)
+    auto wargv = std::unique_ptr<wchar_t *[], decltype(deleter)>(CommandLineToArgvW(GetCommandLineW(), &argc), deleter);
+    // NOLINTEND(*-avoid-c-arrays)
+
+    if(wargv == nullptr) {
+        throw std::runtime_error("CommandLineToArgvW failed with code " + std::to_string(GetLastError()));
+    }
+
+    result.reserve(static_cast<size_t>(argc));
+    for(size_t i = 0; i < static_cast<size_t>(argc); ++i) {
+        result.push_back(narrow(wargv[i]));
+    }
+
+    return result;
+}
+#endif
+
+}  // namespace detail
+
+
+
+
 /// Include the items in this namespace to get free conversion of enums to/from streams.
 /// (This is available inside CLI as well, so CLI11 will use this without a using statement).
 namespace enums {
@@ -270,6 +539,9 @@ inline std::string trim_copy(const std::string &str) {
 /// remove quotes at the front and back of a string either '"' or '\''
 CLI11_INLINE std::string &remove_quotes(std::string &str);
 
+/// remove quotes from all elements of a string vector and process escaped components
+CLI11_INLINE void remove_quotes(std::vector<std::string> &args);
+
 /// Add a leader to the beginning of all new lines (nothing is added
 /// at the start of the first line). `"; "` would be for ini files
 ///
@@ -290,14 +562,16 @@ CLI11_INLINE std::ostream &format_aliases(std::ostream &out, const std::vector<s
 
 /// Verify the first character of an option
 /// - is a trigger character, ! has special meaning and new lines would just be annoying to deal with
-template <typename T> bool valid_first_char(T c) { return ((c != '-') && (c != '!') && (c != ' ') && c != '\n'); }
+template <typename T> bool valid_first_char(T c) {
+    return ((c != '-') && (static_cast<unsigned char>(c) > 33));  // space and '!' not allowed
+}
 
 /// Verify following characters of an option
 template <typename T> bool valid_later_char(T c) {
     // = and : are value separators, { has special meaning for option defaults,
-    // and \n would just be annoying to deal with in many places allowing space here has too much potential for
-    // inadvertent entry errors and bugs
-    return ((c != '=') && (c != ':') && (c != '{') && (c != ' ') && c != '\n');
+    // and control codes other than tab would just be annoying to deal with in many places allowing space here has too
+    // much potential for inadvertent entry errors and bugs
+    return ((c != '=') && (c != ':') && (c != '{') && ((static_cast<unsigned char>(c) > 32) || c == '\t'));
 }
 
 /// Verify an option/subcommand name
@@ -360,18 +634,46 @@ template <typename Callable> inline std::string find_and_modify(std::string str,
     return str;
 }
 
+/// close a sequence of characters indicated by a closure character.  Brackets allows sub sequences
+/// recognized bracket sequences include "'`[(<{  other closure characters are assumed to be literal strings
+CLI11_INLINE std::size_t close_sequence(const std::string &str, std::size_t start, char closure_char);
+
 /// Split a string '"one two" "three"' into 'one two', 'three'
-/// Quote characters can be ` ' or "
+/// Quote characters can be ` ' or " or bracket characters [{(< with matching to the matching bracket
 CLI11_INLINE std::vector<std::string> split_up(std::string str, char delimiter = '\0');
 
+/// get the value of an environmental variable or empty string if empty
+CLI11_INLINE std::string get_environment_value(const std::string &env_name);
+
 /// This function detects an equal or colon followed by an escaped quote after an argument
 /// then modifies the string to replace the equality with a space.  This is needed
 /// to allow the split up function to work properly and is intended to be used with the find_and_modify function
 /// the return value is the offset+1 which is required by the find_and_modify function.
 CLI11_INLINE std::size_t escape_detect(std::string &str, std::size_t offset);
 
-/// Add quotes if the string contains spaces
-CLI11_INLINE std::string &add_quotes_if_needed(std::string &str);
+/// @brief  detect if a string has escapable characters
+/// @param str the string to do the detection on
+/// @return true if the string has escapable characters
+CLI11_INLINE bool has_escapable_character(const std::string &str);
+
+/// @brief escape all escapable characters
+/// @param str the string to escape
+/// @return a string with the escapble characters escaped with '\'
+CLI11_INLINE std::string add_escaped_characters(const std::string &str);
+
+/// @brief replace the escaped characters with their equivalent
+CLI11_INLINE std::string remove_escaped_characters(const std::string &str);
+
+/// generate a string with all non printable characters escaped to hex codes
+CLI11_INLINE std::string binary_escape_string(const std::string &string_to_escape);
+
+CLI11_INLINE bool is_binary_escaped_string(const std::string &escaped_string);
+
+/// extract an escaped binary_string
+CLI11_INLINE std::string extract_binary_string(const std::string &escaped_string);
+
+/// process a quoted string, remove the quotes and if appropriate handle escaped characters
+CLI11_INLINE bool process_quoted_string(std::string &str, char string_char = '\"', char literal_char = '\'');
 
 }  // namespace detail
 
@@ -421,7 +723,17 @@ CLI11_INLINE std::string &rtrim(std::string &str, const std::string &filter) {
 }
 
 CLI11_INLINE std::string &remove_quotes(std::string &str) {
-    if(str.length() > 1 && (str.front() == '"' || str.front() == '\'')) {
+    if(str.length() > 1 && (str.front() == '"' || str.front() == '\'' || str.front() == '`')) {
+        if(str.front() == str.back()) {
+            str.pop_back();
+            str.erase(str.begin(), str.begin() + 1);
+        }
+    }
+    return str;
+}
+
+CLI11_INLINE std::string &remove_outer(std::string &str, char key) {
+    if(str.length() > 1 && (str.front() == key)) {
         if(str.front() == str.back()) {
             str.pop_back();
             str.erase(str.begin(), str.begin() + 1);
@@ -541,37 +853,220 @@ find_member(std::string name, const std::vector<std::string> names, bool ignore_
     return (it != std::end(names)) ? (it - std::begin(names)) : (-1);
 }
 
+static const std::string escapedChars("\b\t\n\f\r\"\\");
+static const std::string escapedCharsCode("btnfr\"\\");
+static const std::string bracketChars{"\"'`[(<{"};
+static const std::string matchBracketChars("\"'`])>}");
+
+CLI11_INLINE bool has_escapable_character(const std::string &str) {
+    return (str.find_first_of(escapedChars) != std::string::npos);
+}
+
+CLI11_INLINE std::string add_escaped_characters(const std::string &str) {
+    std::string out;
+    out.reserve(str.size() + 4);
+    for(char s : str) {
+        auto sloc = escapedChars.find_first_of(s);
+        if(sloc != std::string::npos) {
+            out.push_back('\\');
+            out.push_back(escapedCharsCode[sloc]);
+        } else {
+            out.push_back(s);
+        }
+    }
+    return out;
+}
+
+CLI11_INLINE std::uint32_t hexConvert(char hc) {
+    int hcode{0};
+    if(hc >= '0' && hc <= '9') {
+        hcode = (hc - '0');
+    } else if(hc >= 'A' && hc <= 'F') {
+        hcode = (hc - 'A' + 10);
+    } else if(hc >= 'a' && hc <= 'f') {
+        hcode = (hc - 'a' + 10);
+    } else {
+        hcode = -1;
+    }
+    return static_cast<uint32_t>(hcode);
+}
+
+CLI11_INLINE char make_char(std::uint32_t code) { return static_cast<char>(static_cast<unsigned char>(code)); }
+
+CLI11_INLINE void append_codepoint(std::string &str, std::uint32_t code) {
+    if(code < 0x80) {  // ascii code equivalent
+        str.push_back(static_cast<char>(code));
+    } else if(code < 0x800) {  // \u0080 to \u07FF
+        // 110yyyyx 10xxxxxx; 0x3f == 0b0011'1111
+        str.push_back(make_char(0xC0 | code >> 6));
+        str.push_back(make_char(0x80 | (code & 0x3F)));
+    } else if(code < 0x10000) {  // U+0800...U+FFFF
+        if(0xD800 <= code && code <= 0xDFFF) {
+            throw std::invalid_argument("[0xD800, 0xDFFF] are not valid UTF-8.");
+        }
+        // 1110yyyy 10yxxxxx 10xxxxxx
+        str.push_back(make_char(0xE0 | code >> 12));
+        str.push_back(make_char(0x80 | (code >> 6 & 0x3F)));
+        str.push_back(make_char(0x80 | (code & 0x3F)));
+    } else if(code < 0x110000) {  // U+010000 ... U+10FFFF
+        // 11110yyy 10yyxxxx 10xxxxxx 10xxxxxx
+        str.push_back(make_char(0xF0 | code >> 18));
+        str.push_back(make_char(0x80 | (code >> 12 & 0x3F)));
+        str.push_back(make_char(0x80 | (code >> 6 & 0x3F)));
+        str.push_back(make_char(0x80 | (code & 0x3F)));
+    }
+}
+
+CLI11_INLINE std::string remove_escaped_characters(const std::string &str) {
+
+    std::string out;
+    out.reserve(str.size());
+    for(auto loc = str.begin(); loc < str.end(); ++loc) {
+        if(*loc == '\\') {
+            if(str.end() - loc < 2) {
+                throw std::invalid_argument("invalid escape sequence " + str);
+            }
+            auto ecloc = escapedCharsCode.find_first_of(*(loc + 1));
+            if(ecloc != std::string::npos) {
+                out.push_back(escapedChars[ecloc]);
+                ++loc;
+            } else if(*(loc + 1) == 'u') {
+                // must have 4 hex characters
+                if(str.end() - loc < 6) {
+                    throw std::invalid_argument("unicode sequence must have 4 hex codes " + str);
+                }
+                std::uint32_t code{0};
+                std::uint32_t mplier{16 * 16 * 16};
+                for(int ii = 2; ii < 6; ++ii) {
+                    std::uint32_t res = hexConvert(*(loc + ii));
+                    if(res > 0x0F) {
+                        throw std::invalid_argument("unicode sequence must have 4 hex codes " + str);
+                    }
+                    code += res * mplier;
+                    mplier = mplier / 16;
+                }
+                append_codepoint(out, code);
+                loc += 5;
+            } else if(*(loc + 1) == 'U') {
+                // must have 8 hex characters
+                if(str.end() - loc < 10) {
+                    throw std::invalid_argument("unicode sequence must have 8 hex codes " + str);
+                }
+                std::uint32_t code{0};
+                std::uint32_t mplier{16 * 16 * 16 * 16 * 16 * 16 * 16};
+                for(int ii = 2; ii < 10; ++ii) {
+                    std::uint32_t res = hexConvert(*(loc + ii));
+                    if(res > 0x0F) {
+                        throw std::invalid_argument("unicode sequence must have 8 hex codes " + str);
+                    }
+                    code += res * mplier;
+                    mplier = mplier / 16;
+                }
+                append_codepoint(out, code);
+                loc += 9;
+            } else if(*(loc + 1) == '0') {
+                out.push_back('\0');
+                ++loc;
+            } else {
+                throw std::invalid_argument(std::string("unrecognized escape sequence \\") + *(loc + 1) + " in " + str);
+            }
+        } else {
+            out.push_back(*loc);
+        }
+    }
+    return out;
+}
+
+CLI11_INLINE std::size_t close_string_quote(const std::string &str, std::size_t start, char closure_char) {
+    std::size_t loc{0};
+    for(loc = start + 1; loc < str.size(); ++loc) {
+        if(str[loc] == closure_char) {
+            break;
+        }
+        if(str[loc] == '\\') {
+            // skip the next character for escaped sequences
+            ++loc;
+        }
+    }
+    return loc;
+}
+
+CLI11_INLINE std::size_t close_literal_quote(const std::string &str, std::size_t start, char closure_char) {
+    auto loc = str.find_first_of(closure_char, start + 1);
+    return (loc != std::string::npos ? loc : str.size());
+}
+
+CLI11_INLINE std::size_t close_sequence(const std::string &str, std::size_t start, char closure_char) {
+
+    auto bracket_loc = matchBracketChars.find(closure_char);
+    switch(bracket_loc) {
+    case 0:
+        return close_string_quote(str, start, closure_char);
+    case 1:
+    case 2:
+    case std::string::npos:
+        return close_literal_quote(str, start, closure_char);
+    default:
+        break;
+    }
+
+    std::string closures(1, closure_char);
+    auto loc = start + 1;
+
+    while(loc < str.size()) {
+        if(str[loc] == closures.back()) {
+            closures.pop_back();
+            if(closures.empty()) {
+                return loc;
+            }
+        }
+        bracket_loc = bracketChars.find(str[loc]);
+        if(bracket_loc != std::string::npos) {
+            switch(bracket_loc) {
+            case 0:
+                loc = close_string_quote(str, loc, str[loc]);
+                break;
+            case 1:
+            case 2:
+                loc = close_literal_quote(str, loc, str[loc]);
+                break;
+            default:
+                closures.push_back(matchBracketChars[bracket_loc]);
+                break;
+            }
+        }
+        ++loc;
+    }
+    if(loc > str.size()) {
+        loc = str.size();
+    }
+    return loc;
+}
+
 CLI11_INLINE std::vector<std::string> split_up(std::string str, char delimiter) {
 
-    const std::string delims("\'\"`");
     auto find_ws = [delimiter](char ch) {
         return (delimiter == '\0') ? std::isspace<char>(ch, std::locale()) : (ch == delimiter);
     };
     trim(str);
 
     std::vector<std::string> output;
-    bool embeddedQuote = false;
-    char keyChar = ' ';
     while(!str.empty()) {
-        if(delims.find_first_of(str[0]) != std::string::npos) {
-            keyChar = str[0];
-            auto end = str.find_first_of(keyChar, 1);
-            while((end != std::string::npos) && (str[end - 1] == '\\')) {  // deal with escaped quotes
-                end = str.find_first_of(keyChar, end + 1);
-                embeddedQuote = true;
-            }
-            if(end != std::string::npos) {
-                output.push_back(str.substr(1, end - 1));
+        if(bracketChars.find_first_of(str[0]) != std::string::npos) {
+            auto bracketLoc = bracketChars.find_first_of(str[0]);
+            auto end = close_sequence(str, 0, matchBracketChars[bracketLoc]);
+            if(end >= str.size()) {
+                output.push_back(std::move(str));
+                str.clear();
+            } else {
+                output.push_back(str.substr(0, end + 1));
                 if(end + 2 < str.size()) {
                     str = str.substr(end + 2);
                 } else {
                     str.clear();
                 }
-
-            } else {
-                output.push_back(str.substr(1));
-                str = "";
             }
+
         } else {
             auto it = std::find_if(std::begin(str), std::end(str), find_ws);
             if(it != std::end(str)) {
@@ -580,14 +1075,9 @@ CLI11_INLINE std::vector<std::string> split_up(std::string str, char delimiter)
                 str = std::string(it + 1, str.end());
             } else {
                 output.push_back(str);
-                str = "";
+                str.clear();
             }
         }
-        // transform any embedded quotes into the regular character
-        if(embeddedQuote) {
-            output.back() = find_and_replace(output.back(), std::string("\\") + keyChar, std::string(1, keyChar));
-            embeddedQuote = false;
-        }
         trim(str);
     }
     return output;
@@ -605,15 +1095,140 @@ CLI11_INLINE std::size_t escape_detect(std::string &str, std::size_t offset) {
     return offset + 1;
 }
 
-CLI11_INLINE std::string &add_quotes_if_needed(std::string &str) {
-    if((str.front() != '"' && str.front() != '\'') || str.front() != str.back()) {
-        char quote = str.find('"') < str.find('\'') ? '\'' : '"';
-        if(str.find(' ') != std::string::npos) {
-            str.insert(0, 1, quote);
-            str.append(1, quote);
+CLI11_INLINE std::string binary_escape_string(const std::string &string_to_escape) {
+    // s is our escaped output string
+    std::string escaped_string{};
+    // loop through all characters
+    for(char c : string_to_escape) {
+        // check if a given character is printable
+        // the cast is necessary to avoid undefined behaviour
+        if(isprint(static_cast<unsigned char>(c)) == 0) {
+            std::stringstream stream;
+            // if the character is not printable
+            // we'll convert it to a hex string using a stringstream
+            // note that since char is signed we have to cast it to unsigned first
+            stream << std::hex << static_cast<unsigned int>(static_cast<unsigned char>(c));
+            std::string code = stream.str();
+            escaped_string += std::string("\\x") + (code.size() < 2 ? "0" : "") + code;
+
+        } else {
+            escaped_string.push_back(c);
         }
     }
-    return str;
+    if(escaped_string != string_to_escape) {
+        auto sqLoc = escaped_string.find('\'');
+        while(sqLoc != std::string::npos) {
+            escaped_string.replace(sqLoc, sqLoc + 1, "\\x27");
+            sqLoc = escaped_string.find('\'');
+        }
+        escaped_string.insert(0, "'B\"(");
+        escaped_string.push_back(')');
+        escaped_string.push_back('"');
+        escaped_string.push_back('\'');
+    }
+    return escaped_string;
+}
+
+CLI11_INLINE bool is_binary_escaped_string(const std::string &escaped_string) {
+    size_t ssize = escaped_string.size();
+    if(escaped_string.compare(0, 3, "B\"(") == 0 && escaped_string.compare(ssize - 2, 2, ")\"") == 0) {
+        return true;
+    }
+    return (escaped_string.compare(0, 4, "'B\"(") == 0 && escaped_string.compare(ssize - 3, 3, ")\"'") == 0);
+}
+
+CLI11_INLINE std::string extract_binary_string(const std::string &escaped_string) {
+    std::size_t start{0};
+    std::size_t tail{0};
+    size_t ssize = escaped_string.size();
+    if(escaped_string.compare(0, 3, "B\"(") == 0 && escaped_string.compare(ssize - 2, 2, ")\"") == 0) {
+        start = 3;
+        tail = 2;
+    } else if(escaped_string.compare(0, 4, "'B\"(") == 0 && escaped_string.compare(ssize - 3, 3, ")\"'") == 0) {
+        start = 4;
+        tail = 3;
+    }
+
+    if(start == 0) {
+        return escaped_string;
+    }
+    std::string outstring;
+
+    outstring.reserve(ssize - start - tail);
+    std::size_t loc = start;
+    while(loc < ssize - tail) {
+        // ssize-2 to skip )" at the end
+        if(escaped_string[loc] == '\\' && (escaped_string[loc + 1] == 'x' || escaped_string[loc + 1] == 'X')) {
+            auto c1 = escaped_string[loc + 2];
+            auto c2 = escaped_string[loc + 3];
+
+            std::uint32_t res1 = hexConvert(c1);
+            std::uint32_t res2 = hexConvert(c2);
+            if(res1 <= 0x0F && res2 <= 0x0F) {
+                loc += 4;
+                outstring.push_back(static_cast<char>(res1 * 16 + res2));
+                continue;
+            }
+        }
+        outstring.push_back(escaped_string[loc]);
+        ++loc;
+    }
+    return outstring;
+}
+
+CLI11_INLINE void remove_quotes(std::vector<std::string> &args) {
+    for(auto &arg : args) {
+        if(arg.front() == '\"' && arg.back() == '\"') {
+            remove_quotes(arg);
+            // only remove escaped for string arguments not literal strings
+            arg = remove_escaped_characters(arg);
+        } else {
+            remove_quotes(arg);
+        }
+    }
+}
+
+CLI11_INLINE bool process_quoted_string(std::string &str, char string_char, char literal_char) {
+    if(str.size() <= 1) {
+        return false;
+    }
+    if(detail::is_binary_escaped_string(str)) {
+        str = detail::extract_binary_string(str);
+        return true;
+    }
+    if(str.front() == string_char && str.back() == string_char) {
+        detail::remove_outer(str, string_char);
+        if(str.find_first_of('\\') != std::string::npos) {
+            str = detail::remove_escaped_characters(str);
+        }
+        return true;
+    }
+    if((str.front() == literal_char || str.front() == '`') && str.back() == str.front()) {
+        detail::remove_outer(str, str.front());
+        return true;
+    }
+    return false;
+}
+
+std::string get_environment_value(const std::string &env_name) {
+    char *buffer = nullptr;
+    std::string ename_string;
+
+#ifdef _MSC_VER
+    // Windows version
+    std::size_t sz = 0;
+    if(_dupenv_s(&buffer, &sz, env_name.c_str()) == 0 && buffer != nullptr) {
+        ename_string = std::string(buffer);
+        free(buffer);
+    }
+#else
+    // This also works on Windows, but gives a warning
+    buffer = std::getenv(env_name.c_str());
+    if(buffer != nullptr) {
+        ename_string = std::string(buffer);
+    }
+#endif
+    return ename_string;
 }
 
 }  // namespace detail
@@ -722,7 +1337,13 @@ class BadNameString : public ConstructionError {
     CLI11_ERROR_DEF(ConstructionError, BadNameString)
     CLI11_ERROR_SIMPLE(BadNameString)
     static BadNameString OneCharName(std::string name) { return BadNameString("Invalid one char name: " + name); }
+    static BadNameString MissingDash(std::string name) {
+        return BadNameString("Long names strings require 2 dashes " + name);
+    }
     static BadNameString BadLongName(std::string name) { return BadNameString("Bad long name: " + name); }
+    static BadNameString BadPositionalName(std::string name) {
+        return BadNameString("Invalid positional Name: " + name);
+    }
     static BadNameString DashesOnly(std::string name) {
         return BadNameString("Must have a name, not just dashes: " + name);
     }
@@ -1087,12 +1708,20 @@ template <typename T, typename C> class is_direct_constructible {
     static auto test(int, std::true_type) -> decltype(
 // NVCC warns about narrowing conversions here
 #ifdef __CUDACC__
+#ifdef __NVCC_DIAG_PRAGMA_SUPPORT__
+#pragma nv_diag_suppress 2361
+#else
 #pragma diag_suppress 2361
 #endif
+#endif
         TT{std::declval<CC>()}
 #ifdef __CUDACC__
+#ifdef __NVCC_DIAG_PRAGMA_SUPPORT__
+#pragma nv_diag_default 2361
+#else
 #pragma diag_default 2361
 #endif
+#endif
         ,
         std::is_move_assignable<TT>());
 
@@ -1171,8 +1800,10 @@ struct is_mutable_container<
                          decltype(std::declval<T>().clear()),
                          decltype(std::declval<T>().insert(std::declval<decltype(std::declval<T>().end())>(),
                                                            std::declval<const typename T::value_type &>()))>,
-                  void>>
-    : public conditional_t<std::is_constructible<T, std::string>::value, std::false_type, std::true_type> {};
+                  void>> : public conditional_t<std::is_constructible<T, std::string>::value ||
+                                                    std::is_constructible<T, std::wstring>::value,
+                                                std::false_type,
+                                                std::true_type> {};
 
 // check to see if an object is a mutable container (fail by default)
 template <typename T, typename _ = void> struct is_readable_container : std::false_type {};
@@ -1475,6 +2106,8 @@ enum class object_category : int {
     // string like types
     string_assignable = 23,
     string_constructible = 24,
+    wstring_assignable = 25,
+    wstring_constructible = 26,
     other = 45,
     // special wrapper or container types
     wrapper_value = 50,
@@ -1523,12 +2156,23 @@ template <typename T> struct classify_object<T, typename std::enable_if<is_bool<
 template <typename T> struct classify_object<T, typename std::enable_if<std::is_floating_point<T>::value>::type> {
     static constexpr object_category value{object_category::floating_point};
 };
+#if defined _MSC_VER
+// in MSVC wstring should take precedence if available this isn't as useful on other compilers due to the broader use of
+// utf-8 encoding
+#define WIDE_STRING_CHECK                                                                                              \
+    !std::is_assignable<T &, std::wstring>::value && !std::is_constructible<T, std::wstring>::value
+#define STRING_CHECK true
+#else
+#define WIDE_STRING_CHECK true
+#define STRING_CHECK !std::is_assignable<T &, std::string>::value && !std::is_constructible<T, std::string>::value
+#endif
 
 /// String and similar direct assignment
 template <typename T>
-struct classify_object<T,
-                       typename std::enable_if<!std::is_floating_point<T>::value && !std::is_integral<T>::value &&
-                                               std::is_assignable<T &, std::string>::value>::type> {
+struct classify_object<
+    T,
+    typename std::enable_if<!std::is_floating_point<T>::value && !std::is_integral<T>::value && WIDE_STRING_CHECK &&
+                            std::is_assignable<T &, std::string>::value>::type> {
     static constexpr object_category value{object_category::string_assignable};
 };
 
@@ -1538,10 +2182,27 @@ struct classify_object<
     T,
     typename std::enable_if<!std::is_floating_point<T>::value && !std::is_integral<T>::value &&
                             !std::is_assignable<T &, std::string>::value && (type_count<T>::value == 1) &&
-                            std::is_constructible<T, std::string>::value>::type> {
+                            WIDE_STRING_CHECK && std::is_constructible<T, std::string>::value>::type> {
     static constexpr object_category value{object_category::string_constructible};
 };
 
+/// Wide strings
+template <typename T>
+struct classify_object<T,
+                       typename std::enable_if<!std::is_floating_point<T>::value && !std::is_integral<T>::value &&
+                                               STRING_CHECK && std::is_assignable<T &, std::wstring>::value>::type> {
+    static constexpr object_category value{object_category::wstring_assignable};
+};
+
+template <typename T>
+struct classify_object<
+    T,
+    typename std::enable_if<!std::is_floating_point<T>::value && !std::is_integral<T>::value &&
+                            !std::is_assignable<T &, std::wstring>::value && (type_count<T>::value == 1) &&
+                            STRING_CHECK && std::is_constructible<T, std::wstring>::value>::type> {
+    static constexpr object_category value{object_category::wstring_constructible};
+};
+
 /// Enumerations
 template <typename T> struct classify_object<T, typename std::enable_if<std::is_enum<T>::value>::type> {
     static constexpr object_category value{object_category::enumeration};
@@ -1554,12 +2215,13 @@ template <typename T> struct classify_object<T, typename std::enable_if<is_compl
 /// Handy helper to contain a bunch of checks that rule out many common types (integers, string like, floating point,
 /// vectors, and enumerations
 template <typename T> struct uncommon_type {
-    using type = typename std::conditional<!std::is_floating_point<T>::value && !std::is_integral<T>::value &&
-                                               !std::is_assignable<T &, std::string>::value &&
-                                               !std::is_constructible<T, std::string>::value && !is_complex<T>::value &&
-                                               !is_mutable_container<T>::value && !std::is_enum<T>::value,
-                                           std::true_type,
-                                           std::false_type>::type;
+    using type = typename std::conditional<
+        !std::is_floating_point<T>::value && !std::is_integral<T>::value &&
+            !std::is_assignable<T &, std::string>::value && !std::is_constructible<T, std::string>::value &&
+            !std::is_assignable<T &, std::wstring>::value && !std::is_constructible<T, std::wstring>::value &&
+            !is_complex<T>::value && !is_mutable_container<T>::value && !std::is_enum<T>::value,
+        std::true_type,
+        std::false_type>::type;
     static constexpr bool value = type::value;
 };
 
@@ -1748,7 +2410,7 @@ bool integral_conversion(const std::string &input, T &output) noexcept {
     if(input.empty() || input.front() == '-') {
         return false;
     }
-    char *val = nullptr;
+    char *val{nullptr};
     errno = 0;
     std::uint64_t output_ll = std::strtoull(input.c_str(), &val, 0);
     if(errno == ERANGE) {
@@ -1764,6 +2426,33 @@ bool integral_conversion(const std::string &input, T &output) noexcept {
         output = (output_sll < 0) ? static_cast<T>(0) : static_cast<T>(output_sll);
         return (static_cast<std::int64_t>(output) == output_sll);
     }
+    // remove separators
+    if(input.find_first_of("_'") != std::string::npos) {
+        std::string nstring = input;
+        nstring.erase(std::remove(nstring.begin(), nstring.end(), '_'), nstring.end());
+        nstring.erase(std::remove(nstring.begin(), nstring.end(), '\''), nstring.end());
+        return integral_conversion(nstring, output);
+    }
+    if(input.compare(0, 2, "0o") == 0) {
+        val = nullptr;
+        errno = 0;
+        output_ll = std::strtoull(input.c_str() + 2, &val, 8);
+        if(errno == ERANGE) {
+            return false;
+        }
+        output = static_cast<T>(output_ll);
+        return (val == (input.c_str() + input.size()) && static_cast<std::uint64_t>(output) == output_ll);
+    }
+    if(input.compare(0, 2, "0b") == 0) {
+        val = nullptr;
+        errno = 0;
+        output_ll = std::strtoull(input.c_str() + 2, &val, 2);
+        if(errno == ERANGE) {
+            return false;
+        }
+        output = static_cast<T>(output_ll);
+        return (val == (input.c_str() + input.size()) && static_cast<std::uint64_t>(output) == output_ll);
+    }
     return false;
 }
 
@@ -1788,11 +2477,38 @@ bool integral_conversion(const std::string &input, T &output) noexcept {
         output = static_cast<T>(1);
         return true;
     }
+    // remove separators
+    if(input.find_first_of("_'") != std::string::npos) {
+        std::string nstring = input;
+        nstring.erase(std::remove(nstring.begin(), nstring.end(), '_'), nstring.end());
+        nstring.erase(std::remove(nstring.begin(), nstring.end(), '\''), nstring.end());
+        return integral_conversion(nstring, output);
+    }
+    if(input.compare(0, 2, "0o") == 0) {
+        val = nullptr;
+        errno = 0;
+        output_ll = std::strtoll(input.c_str() + 2, &val, 8);
+        if(errno == ERANGE) {
+            return false;
+        }
+        output = static_cast<T>(output_ll);
+        return (val == (input.c_str() + input.size()) && static_cast<std::int64_t>(output) == output_ll);
+    }
+    if(input.compare(0, 2, "0b") == 0) {
+        val = nullptr;
+        errno = 0;
+        output_ll = std::strtoll(input.c_str() + 2, &val, 2);
+        if(errno == ERANGE) {
+            return false;
+        }
+        output = static_cast<T>(output_ll);
+        return (val == (input.c_str() + input.size()) && static_cast<std::int64_t>(output) == output_ll);
+    }
     return false;
 }
 
-/// Convert a flag into an integer value  typically binary flags
-inline std::int64_t to_flag_value(std::string val) {
+/// Convert a flag into an integer value  typically binary flags sets errno to nonzero if conversion failed
+inline std::int64_t to_flag_value(std::string val) noexcept {
     static const std::string trueString("true");
     static const std::string falseString("false");
     if(val == trueString) {
@@ -1820,7 +2536,8 @@ inline std::int64_t to_flag_value(std::string val) {
             ret = 1;
             break;
         default:
-            throw std::invalid_argument("unrecognized character");
+            errno = EINVAL;
+            return -1;
         }
         return ret;
     }
@@ -1829,7 +2546,11 @@ inline std::int64_t to_flag_value(std::string val) {
     } else if(val == falseString || val == "off" || val == "no" || val == "disable") {
         ret = -1;
     } else {
-        ret = std::stoll(val);
+        char *loc_ptr{nullptr};
+        ret = std::strtoll(val.c_str(), &loc_ptr, 0);
+        if(loc_ptr != (val.c_str() + val.size()) && errno == 0) {
+            errno = EINVAL;
+        }
     }
     return ret;
 }
@@ -1858,18 +2579,16 @@ bool lexical_cast(const std::string &input, T &output) {
 template <typename T,
           enable_if_t<classify_object<T>::value == object_category::boolean_value, detail::enabler> = detail::dummy>
 bool lexical_cast(const std::string &input, T &output) {
-    try {
-        auto out = to_flag_value(input);
+    errno = 0;
+    auto out = to_flag_value(input);
+    if(errno == 0) {
         output = (out > 0);
-        return true;
-    } catch(const std::invalid_argument &) {
-        return false;
-    } catch(const std::out_of_range &) {
-        // if the number is out of the range of a 64 bit value then it is still a number and for this purpose is still
-        // valid all we care about the sign
+    } else if(errno == ERANGE) {
         output = (input[0] != '-');
-        return true;
+    } else {
+        return false;
     }
+    return true;
 }
 
 /// Floats
@@ -1882,7 +2601,17 @@ bool lexical_cast(const std::string &input, T &output) {
     char *val = nullptr;
     auto output_ld = std::strtold(input.c_str(), &val);
     output = static_cast<T>(output_ld);
-    return val == (input.c_str() + input.size());
+    if(val == (input.c_str() + input.size())) {
+        return true;
+    }
+    // remove separators
+    if(input.find_first_of("_'") != std::string::npos) {
+        std::string nstring = input;
+        nstring.erase(std::remove(nstring.begin(), nstring.end(), '_'), nstring.end());
+        nstring.erase(std::remove(nstring.begin(), nstring.end(), '\''), nstring.end());
+        return lexical_cast(nstring, output);
+    }
+    return false;
 }
 
 /// complex
@@ -1934,6 +2663,23 @@ bool lexical_cast(const std::string &input, T &output) {
     return true;
 }
 
+/// Wide strings
+template <
+    typename T,
+    enable_if_t<classify_object<T>::value == object_category::wstring_assignable, detail::enabler> = detail::dummy>
+bool lexical_cast(const std::string &input, T &output) {
+    output = widen(input);
+    return true;
+}
+
+template <
+    typename T,
+    enable_if_t<classify_object<T>::value == object_category::wstring_constructible, detail::enabler> = detail::dummy>
+bool lexical_cast(const std::string &input, T &output) {
+    output = T{widen(input)};
+    return true;
+}
+
 /// Enumerations
 template <typename T,
           enable_if_t<classify_object<T>::value == object_category::enumeration, detail::enabler> = detail::dummy>
@@ -2062,7 +2808,9 @@ template <typename AssignTo,
           typename ConvertTo,
           enable_if_t<std::is_same<AssignTo, ConvertTo>::value &&
                           (classify_object<AssignTo>::value == object_category::string_assignable ||
-                           classify_object<AssignTo>::value == object_category::string_constructible),
+                           classify_object<AssignTo>::value == object_category::string_constructible ||
+                           classify_object<AssignTo>::value == object_category::wstring_assignable ||
+                           classify_object<AssignTo>::value == object_category::wstring_constructible),
                       detail::enabler> = detail::dummy>
 bool lexical_assign(const std::string &input, AssignTo &output) {
     return lexical_cast(input, output);
@@ -2073,7 +2821,9 @@ template <typename AssignTo,
           typename ConvertTo,
           enable_if_t<std::is_same<AssignTo, ConvertTo>::value && std::is_assignable<AssignTo &, AssignTo>::value &&
                           classify_object<AssignTo>::value != object_category::string_assignable &&
-                          classify_object<AssignTo>::value != object_category::string_constructible,
+                          classify_object<AssignTo>::value != object_category::string_constructible &&
+                          classify_object<AssignTo>::value != object_category::wstring_assignable &&
+                          classify_object<AssignTo>::value != object_category::wstring_constructible,
                       detail::enabler> = detail::dummy>
 bool lexical_assign(const std::string &input, AssignTo &output) {
     if(input.empty()) {
@@ -2112,9 +2862,17 @@ bool lexical_assign(const std::string &input, AssignTo &output) {
         output = 0;
         return true;
     }
-    int val = 0;
+    int val{0};
     if(lexical_cast(input, val)) {
+#if defined(__clang__)
+/* on some older clang compilers */
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wsign-conversion"
+#endif
         output = val;
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
         return true;
     }
     return false;
@@ -2169,12 +2927,12 @@ template <typename AssignTo,
                       detail::enabler> = detail::dummy>
 bool lexical_conversion(const std::vector<std ::string> &strings, AssignTo &output) {
     // the remove const is to handle pair types coming from a container
-    typename std::remove_const<typename std::tuple_element<0, ConvertTo>::type>::type v1;
-    typename std::tuple_element<1, ConvertTo>::type v2;
-    bool retval = lexical_assign<decltype(v1), decltype(v1)>(strings[0], v1);
-    if(strings.size() > 1) {
-        retval = retval && lexical_assign<decltype(v2), decltype(v2)>(strings[1], v2);
-    }
+    using FirstType = typename std::remove_const<typename std::tuple_element<0, ConvertTo>::type>::type;
+    using SecondType = typename std::tuple_element<1, ConvertTo>::type;
+    FirstType v1;
+    SecondType v2;
+    bool retval = lexical_assign<FirstType, FirstType>(strings[0], v1);
+    retval = retval && lexical_assign<SecondType, SecondType>((strings.size() > 1) ? strings[1] : std::string{}, v2);
     if(retval) {
         output = AssignTo{v1, v2};
     }
@@ -2189,6 +2947,9 @@ template <class AssignTo,
                       detail::enabler> = detail::dummy>
 bool lexical_conversion(const std::vector<std ::string> &strings, AssignTo &output) {
     output.erase(output.begin(), output.end());
+    if(strings.empty()) {
+        return true;
+    }
     if(strings.size() == 1 && strings[0] == "{}") {
         return true;
     }
@@ -2333,7 +3094,7 @@ tuple_type_conversion(std::vector<std::string> &strings, AssignTo &output) {
 
     std::size_t index{subtype_count_min<ConvertTo>::value};
     const std::size_t mx_count{subtype_count<ConvertTo>::value};
-    const std::size_t mx{(std::max)(mx_count, strings.size())};
+    const std::size_t mx{(std::min)(mx_count, strings.size() - 1)};
 
     while(index < mx) {
         if(is_separator(strings[index])) {
@@ -2343,7 +3104,11 @@ tuple_type_conversion(std::vector<std::string> &strings, AssignTo &output) {
     }
     bool retval = lexical_conversion<AssignTo, ConvertTo>(
         std::vector<std::string>(strings.begin(), strings.begin() + static_cast<std::ptrdiff_t>(index)), output);
-    strings.erase(strings.begin(), strings.begin() + static_cast<std::ptrdiff_t>(index) + 1);
+    if(strings.size() > index) {
+        strings.erase(strings.begin(), strings.begin() + static_cast<std::ptrdiff_t>(index) + 1);
+    } else {
+        strings.clear();
+    }
     return retval;
 }
 
@@ -2487,12 +3252,13 @@ inline std::string sum_string_vector(const std::vector<std::string> &values) {
         double tv{0.0};
         auto comp = lexical_cast(arg, tv);
         if(!comp) {
-            try {
-                tv = static_cast<double>(detail::to_flag_value(arg));
-            } catch(const std::exception &) {
-                fail = true;
+            errno = 0;
+            auto fv = detail::to_flag_value(arg);
+            fail = (errno != 0);
+            if(fail) {
                 break;
             }
+            tv = static_cast<double>(fv);
         }
         val += tv;
     }
@@ -2501,13 +3267,10 @@ inline std::string sum_string_vector(const std::vector<std::string> &values) {
             output.append(arg);
         }
     } else {
-        if(val <= static_cast<double>((std::numeric_limits<std::int64_t>::min)()) ||
-           val >= static_cast<double>((std::numeric_limits<std::int64_t>::max)()) ||
-           std::ceil(val) == std::floor(val)) {
-            output = detail::value_string(static_cast<int64_t>(val));
-        } else {
-            output = detail::value_string(val);
-        }
+        std::ostringstream out;
+        out.precision(16);
+        out << val;
+        output = out.str();
     }
     return output;
 }
@@ -2553,7 +3316,7 @@ CLI11_INLINE bool split_short(const std::string &current, std::string &name, std
 }
 
 CLI11_INLINE bool split_long(const std::string &current, std::string &name, std::string &value) {
-    if(current.size() > 2 && current.substr(0, 2) == "--" && valid_first_char(current[2])) {
+    if(current.size() > 2 && current.compare(0, 2, "--") == 0 && valid_first_char(current[2])) {
         auto loc = current.find_first_of('=');
         if(loc != std::string::npos) {
             name = current.substr(2, loc - 2);
@@ -2625,7 +3388,6 @@ get_names(const std::vector<std::string> &input) {
     std::vector<std::string> short_names;
     std::vector<std::string> long_names;
     std::string pos_name;
-
     for(std::string name : input) {
         if(name.length() == 0) {
             continue;
@@ -2633,6 +3395,8 @@ get_names(const std::vector<std::string> &input) {
         if(name.length() > 1 && name[0] == '-' && name[1] != '-') {
             if(name.length() == 2 && valid_first_char(name[1]))
                 short_names.emplace_back(1, name[1]);
+            else if(name.length() > 2)
+                throw BadNameString::MissingDash(name);
             else
                 throw BadNameString::OneCharName(name);
         } else if(name.length() > 2 && name.substr(0, 2) == "--") {
@@ -2644,12 +3408,15 @@ get_names(const std::vector<std::string> &input) {
         } else if(name == "-" || name == "--") {
             throw BadNameString::DashesOnly(name);
         } else {
-            if(pos_name.length() > 0)
+            if(!pos_name.empty())
                 throw BadNameString::MultiPositionalNames(name);
-            pos_name = name;
+            if(valid_name_string(name)) {
+                pos_name = name;
+            } else {
+                throw BadNameString::BadPositionalName(name);
+            }
         }
     }
-
     return std::make_tuple(short_names, long_names, pos_name);
 }
 
@@ -2666,7 +3433,6 @@ struct ConfigItem {
 
     /// This is the name
     std::string name{};
-
     /// Listing of inputs
     std::vector<std::string> inputs{};
 
@@ -2729,8 +3495,8 @@ class ConfigBase : public Config {
     char valueDelimiter = '=';
     /// the character to use around strings
     char stringQuote = '"';
-    /// the character to use around single characters
-    char characterQuote = '\'';
+    /// the character to use around single characters and literal strings
+    char literalQuote = '\'';
     /// the maximum number of layers to allow
     uint8_t maximumLayers{255};
     /// the separator used to separator parent layers
@@ -2766,10 +3532,10 @@ class ConfigBase : public Config {
         valueDelimiter = vSep;
         return this;
     }
-    /// Specify the quote characters used around strings and characters
-    ConfigBase *quoteCharacter(char qString, char qChar) {
+    /// Specify the quote characters used around strings and literal strings
+    ConfigBase *quoteCharacter(char qString, char literalChar) {
         stringQuote = qString;
-        characterQuote = qChar;
+        literalQuote = literalChar;
         return this;
     }
     /// Specify the maximum number of parents
@@ -3001,6 +3767,11 @@ class IPV4Validator : public Validator {
     IPV4Validator();
 };
 
+class EscapedStringTransformer : public Validator {
+  public:
+    EscapedStringTransformer();
+};
+
 }  // namespace detail
 
 // Static is not needed here, because global const implies static.
@@ -3020,6 +3791,9 @@ const detail::NonexistentPathValidator NonexistentPath;
 /// Check for an IP4 address
 const detail::IPV4Validator ValidIPV4;
 
+/// convert escaped characters into their associated values
+const detail::EscapedStringTransformer EscapedString;
+
 /// Validate the input as a particular type
 template <typename DesiredType> class TypeValidator : public Validator {
   public:
@@ -3772,14 +4546,14 @@ namespace detail {
 #if defined CLI11_HAS_FILESYSTEM && CLI11_HAS_FILESYSTEM > 0
 CLI11_INLINE path_type check_path(const char *file) noexcept {
     std::error_code ec;
-    auto stat = std::filesystem::status(file, ec);
+    auto stat = std::filesystem::status(to_path(file), ec);
     if(ec) {
         return path_type::nonexistent;
     }
     switch(stat.type()) {
     case std::filesystem::file_type::none:  // LCOV_EXCL_LINE
     case std::filesystem::file_type::not_found:
-        return path_type::nonexistent;
+        return path_type::nonexistent;  // LCOV_EXCL_LINE
     case std::filesystem::file_type::directory:
         return path_type::directory;
     case std::filesystem::file_type::symlink:
@@ -3873,10 +4647,29 @@ CLI11_INLINE IPV4Validator::IPV4Validator() : Validator("IPV4") {
                 return std::string("Each IP number must be between 0 and 255 ") + var;
             }
         }
-        return std::string();
+        return std::string{};
     };
 }
 
+CLI11_INLINE EscapedStringTransformer::EscapedStringTransformer() {
+    func_ = [](std::string &str) {
+        try {
+            if(str.size() > 1 && (str.front() == '\"' || str.front() == '\'' || str.front() == '`') &&
+               str.front() == str.back()) {
+                process_quoted_string(str);
+            } else if(str.find_first_of('\\') != std::string::npos) {
+                if(detail::is_binary_escaped_string(str)) {
+                    str = detail::extract_binary_string(str);
+                } else {
+                    str = remove_escaped_characters(str);
+                }
+            }
+            return std::string{};
+        } catch(const std::invalid_argument &ia) {
+            return std::string(ia.what());
+        }
+    };
+}
 }  // namespace detail
 
 CLI11_INLINE FileOnDefaultPath::FileOnDefaultPath(std::string default_path, bool enableErrorReturn)
@@ -4175,7 +4968,8 @@ enum class MultiOptionPolicy : char {
     TakeFirst,  //!< take only the first Expected number of arguments
     Join,       //!< merge all the arguments together into a single string via the delimiter character default('\n')
     TakeAll,    //!< just get all the passed argument regardless
-    Sum         //!< sum all the arguments together if numerical or concatenate directly without delimiter
+    Sum,        //!< sum all the arguments together if numerical or concatenate directly without delimiter
+    Reverse,    //!< take only the last Expected number of arguments in reverse order
 };
 
 /// This is the CRTP base class for Option and OptionDefaults. It was designed this way
@@ -4683,12 +5477,12 @@ class Option : public OptionBase<Option> {
         if(!lnames_.empty()) {
             return lnames_[0];
         }
-        if(!pname_.empty()) {
-            return pname_;
-        }
         if(!snames_.empty()) {
             return snames_[0];
         }
+        if(!pname_.empty()) {
+            return pname_;
+        }
         return envname_;
     }
     /// The number of times the option expects to be included
@@ -4711,13 +5505,13 @@ class Option : public OptionBase<Option> {
     CLI11_NODISCARD int get_items_expected() const { return get_items_expected_min(); }
 
     /// True if the argument can be given directly
-    CLI11_NODISCARD bool get_positional() const { return pname_.length() > 0; }
+    CLI11_NODISCARD bool get_positional() const { return !pname_.empty(); }
 
     /// True if option has at least one non-positional name
-    CLI11_NODISCARD bool nonpositional() const { return (snames_.size() + lnames_.size()) > 0; }
+    CLI11_NODISCARD bool nonpositional() const { return (!lnames_.empty() || !snames_.empty()); }
 
     /// True if option has description
-    CLI11_NODISCARD bool has_description() const { return description_.length() > 0; }
+    CLI11_NODISCARD bool has_description() const { return !description_.empty(); }
 
     /// Get the description
     CLI11_NODISCARD const std::string &get_description() const { return description_; }
@@ -5226,13 +6020,29 @@ CLI11_INLINE void Option::run_callback() {
 
 CLI11_NODISCARD CLI11_INLINE const std::string &Option::matching_name(const Option &other) const {
     static const std::string estring;
-    for(const std::string &sname : snames_)
+    for(const std::string &sname : snames_) {
         if(other.check_sname(sname))
             return sname;
-    for(const std::string &lname : lnames_)
+        if(other.check_lname(sname))
+            return sname;
+    }
+    for(const std::string &lname : lnames_) {
         if(other.check_lname(lname))
             return lname;
-
+        if(lname.size() == 1) {
+            if(other.check_sname(lname)) {
+                return lname;
+            }
+        }
+    }
+    if(snames_.empty() && lnames_.empty() && !pname_.empty()) {
+        if(other.check_sname(pname_) || other.check_lname(pname_) || pname_ == other.pname_)
+            return pname_;
+    }
+    if(other.snames_.empty() && other.fnames_.empty() && !other.pname_.empty()) {
+        if(check_sname(other.pname_) || check_lname(other.pname_) || (pname_ == other.pname_))
+            return other.pname_;
+    }
     if(ignore_case_ ||
        ignore_underscore_) {  // We need to do the inverse, in case we are ignore_case or ignore underscore
         for(const std::string &sname : other.snames_)
@@ -5286,6 +6096,9 @@ CLI11_NODISCARD CLI11_INLINE std::string Option::get_flag_value(const std::strin
             if(default_ind >= 0) {
                 // We can static cast this to std::size_t because it is more than 0 in this block
                 if(default_flag_values_[static_cast<std::size_t>(default_ind)].second != input_value) {
+                    if(input_value == default_str_ && force_callback_) {
+                        return input_value;
+                    }
                     throw(ArgumentMismatch::FlagOverride(name));
                 }
             } else {
@@ -5306,15 +6119,15 @@ CLI11_NODISCARD CLI11_INLINE std::string Option::get_flag_value(const std::strin
         return input_value;
     }
     if(default_flag_values_[static_cast<std::size_t>(ind)].second == falseString) {
-        try {
-            auto val = detail::to_flag_value(input_value);
-            return (val == 1) ? falseString : (val == (-1) ? trueString : std::to_string(-val));
-        } catch(const std::invalid_argument &) {
+        errno = 0;
+        auto val = detail::to_flag_value(input_value);
+        if(errno != 0) {
+            errno = 0;
             return input_value;
         }
-    } else {
-        return input_value;
+        return (val == 1) ? falseString : (val == (-1) ? trueString : std::to_string(-val));
     }
+    return input_value;
 }
 
 CLI11_INLINE Option *Option::add_result(std::string s) {
@@ -5417,7 +6230,8 @@ CLI11_INLINE void Option::_validate_results(results_t &res) const {
         if(type_size_max_ > 1) {  // in this context index refers to the index in the type
             int index = 0;
             if(get_items_expected_max() < static_cast<int>(res.size()) &&
-               multi_option_policy_ == CLI::MultiOptionPolicy::TakeLast) {
+               (multi_option_policy_ == CLI::MultiOptionPolicy::TakeLast ||
+                multi_option_policy_ == CLI::MultiOptionPolicy::Reverse)) {
                 // create a negative index for the earliest ones
                 index = get_items_expected_max() - static_cast<int>(res.size());
             }
@@ -5435,7 +6249,8 @@ CLI11_INLINE void Option::_validate_results(results_t &res) const {
         } else {
             int index = 0;
             if(expected_max_ < static_cast<int>(res.size()) &&
-               multi_option_policy_ == CLI::MultiOptionPolicy::TakeLast) {
+               (multi_option_policy_ == CLI::MultiOptionPolicy::TakeLast ||
+                multi_option_policy_ == CLI::MultiOptionPolicy::Reverse)) {
                 // create a negative index for the earliest ones
                 index = expected_max_ - static_cast<int>(res.size());
             }
@@ -5467,6 +6282,15 @@ CLI11_INLINE void Option::_reduce_results(results_t &out, const results_t &origi
             out.assign(original.end() - static_cast<results_t::difference_type>(trim_size), original.end());
         }
     } break;
+    case MultiOptionPolicy::Reverse: {
+        // Allow multi-option sizes (including 0)
+        std::size_t trim_size = std::min<std::size_t>(
+            static_cast<std::size_t>(std::max<int>(get_items_expected_max(), 1)), original.size());
+        if(original.size() != trim_size || trim_size > 1) {
+            out.assign(original.end() - static_cast<results_t::difference_type>(trim_size), original.end());
+        }
+        std::reverse(out.begin(), out.end());
+    } break;
     case MultiOptionPolicy::TakeFirst: {
         std::size_t trim_size = std::min<std::size_t>(
             static_cast<std::size_t>(std::max<int>(get_items_expected_max(), 1)), original.size());
@@ -5496,7 +6320,12 @@ CLI11_INLINE void Option::_reduce_results(results_t &out, const results_t &origi
             throw ArgumentMismatch::AtLeast(get_name(), static_cast<int>(num_min), original.size());
         }
         if(original.size() > num_max) {
-            throw ArgumentMismatch::AtMost(get_name(), static_cast<int>(num_max), original.size());
+            if(original.size() == 2 && num_max == 1 && original[1] == "%%" && original[0] == "{}") {
+                // this condition is a trap for the following empty indicator check on config files
+                out = original;
+            } else {
+                throw ArgumentMismatch::AtMost(get_name(), static_cast<int>(num_max), original.size());
+            }
         }
         break;
     }
@@ -5505,11 +6334,11 @@ CLI11_INLINE void Option::_reduce_results(results_t &out, const results_t &origi
     // {} is the indicator for an empty container
     if(out.empty()) {
         if(original.size() == 1 && original[0] == "{}" && get_items_expected_min() > 0) {
-            out.push_back("{}");
-            out.push_back("%%");
+            out.emplace_back("{}");
+            out.emplace_back("%%");
         }
     } else if(out.size() == 1 && out[0] == "{}" && get_items_expected_min() > 0) {
-        out.push_back("%%");
+        out.emplace_back("%%");
     }
 }
 
@@ -5570,9 +6399,9 @@ CLI11_INLINE int Option::_add_result(std::string &&result, std::vector<std::stri
 
 
 #ifndef CLI11_PARSE
-#define CLI11_PARSE(app, argc, argv)                                                                                   \
+#define CLI11_PARSE(app, ...)                                                                                          \
     try {                                                                                                              \
-        (app).parse((argc), (argv));                                                                                   \
+        (app).parse(__VA_ARGS__);                                                                                      \
     } catch(const CLI::ParseError &e) {                                                                                \
         return (app).exit(e);                                                                                          \
     }
@@ -5685,6 +6514,12 @@ class App {
     /// @name Help
     ///@{
 
+    /// Usage to put after program/subcommand description in the help output INHERITABLE
+    std::string usage_{};
+
+    /// This is a function that generates a usage to put after program/subcommand description in help output
+    std::function<std::string()> usage_callback_{};
+
     /// Footer to put after all options in the help output INHERITABLE
     std::string footer_{};
 
@@ -5819,6 +6654,14 @@ class App {
 
     ///@}
 
+#ifdef _WIN32
+    /// When normalizing argv to UTF-8 on Windows, this is the storage for normalized args.
+    std::vector<std::string> normalized_argv_{};
+
+    /// When normalizing argv to UTF-8 on Windows, this is the `char**` value returned to the user.
+    std::vector<char *> normalized_argv_view_{};
+#endif
+
     /// Special private constructor for subcommand
     App(std::string app_description, std::string app_name, App *parent);
 
@@ -5838,6 +6681,9 @@ class App {
     /// virtual destructor
     virtual ~App() = default;
 
+    /// Convert the contents of argv to UTF-8. Only does something on Windows, does nothing elsewhere.
+    CLI11_NODISCARD char **ensure_utf8(char **argv);
+
     /// Set a callback for execution when all parsing and processing has completed
     ///
     /// Due to a bug in c++11,
@@ -6369,12 +7215,18 @@ class App {
     /// Parses the command line - throws errors.
     /// This must be called after the options are in but before the rest of the program.
     void parse(int argc, const char *const *argv);
+    void parse(int argc, const wchar_t *const *argv);
+
+  private:
+    template <class CharT> void parse_char_t(int argc, const CharT *const *argv);
 
+  public:
     /// Parse a single string as if it contained command line arguments.
     /// This function splits the string into arguments then calls parse(std::vector<std::string> &)
     /// the function takes an optional boolean argument specifying if the programName is included in the string to
     /// process
     void parse(std::string commandline, bool program_name_included = false);
+    void parse(std::wstring commandline, bool program_name_included = false);
 
     /// The real work is done here. Expects a reversed vector.
     /// Changes the vector to the remaining options.
@@ -6482,6 +7334,16 @@ class App {
     /// @name Help
     ///@{
 
+    /// Set usage.
+    App *usage(std::string usage_string) {
+        usage_ = std::move(usage_string);
+        return this;
+    }
+    /// Set usage.
+    App *usage(std::function<std::string()> usage_function) {
+        usage_callback_ = std::move(usage_function);
+        return this;
+    }
     /// Set footer.
     App *footer(std::string footer_string) {
         footer_ = std::move(footer_string);
@@ -6590,6 +7452,11 @@ class App {
     /// Get the group of this subcommand
     CLI11_NODISCARD const std::string &get_group() const { return group_; }
 
+    /// Generate and return the usage.
+    CLI11_NODISCARD std::string get_usage() const {
+        return (usage_callback_) ? usage_callback_() + '\n' + usage_ : usage_;
+    }
+
     /// Generate and return the footer.
     CLI11_NODISCARD std::string get_footer() const {
         return (footer_callback_) ? footer_callback_() + '\n' + footer_ : footer_;
@@ -6727,6 +7594,9 @@ class App {
     /// Read and process a configuration file (main app only)
     void _process_config_file();
 
+    /// Read and process a particular configuration file
+    bool _process_config_file(const std::string &config_file, bool throw_error);
+
     /// Get envname options if not yet passed. Runs on *all* subcommands.
     void _process_env();
 
@@ -6799,8 +7669,9 @@ class App {
     bool _parse_subcommand(std::vector<std::string> &args);
 
     /// Parse a short (false) or long (true) argument, must be at the top of the list
+    /// if local_processing_only is set to true then fallthrough is disabled will return false if not found
     /// return true if the argument was processed or false if nothing was done
-    bool _parse_arg(std::vector<std::string> &args, detail::Classifier current_type);
+    bool _parse_arg(std::vector<std::string> &args, detail::Classifier current_type, bool local_processing_only);
 
     /// Trigger the pre_parse callback if needed
     void _trigger_pre_parse(std::size_t remaining_args);
@@ -6955,6 +7826,7 @@ CLI11_INLINE App::App(std::string app_description, std::string app_name, App *pa
         configurable_ = parent_->configurable_;
         allow_windows_style_options_ = parent_->allow_windows_style_options_;
         group_ = parent_->group_;
+        usage_ = parent_->usage_;
         footer_ = parent_->footer_;
         formatter_ = parent_->formatter_;
         config_formatter_ = parent_->config_formatter_;
@@ -6962,10 +7834,32 @@ CLI11_INLINE App::App(std::string app_description, std::string app_name, App *pa
     }
 }
 
+CLI11_NODISCARD CLI11_INLINE char **App::ensure_utf8(char **argv) {
+#ifdef _WIN32
+    (void)argv;
+
+    normalized_argv_ = detail::compute_win32_argv();
+
+    if(!normalized_argv_view_.empty()) {
+        normalized_argv_view_.clear();
+    }
+
+    normalized_argv_view_.reserve(normalized_argv_.size());
+    for(auto &arg : normalized_argv_) {
+        // using const_cast is well-defined, string is known to not be const.
+        normalized_argv_view_.push_back(const_cast<char *>(arg.data()));
+    }
+
+    return normalized_argv_view_.data();
+#else
+    return argv;
+#endif
+}
+
 CLI11_INLINE App *App::name(std::string app_name) {
 
     if(parent_ != nullptr) {
-        auto oname = name_;
+        std::string oname = name_;
         name_ = app_name;
         const auto &res = _compare_subcommand_names(*this, *_get_fallthrough_parent());
         if(!res.empty()) {
@@ -7046,6 +7940,32 @@ CLI11_INLINE Option *App::add_option(std::string option_name,
 
     if(std::find_if(std::begin(options_), std::end(options_), [&myopt](const Option_p &v) { return *v == myopt; }) ==
        std::end(options_)) {
+        if(myopt.lnames_.empty() && myopt.snames_.empty()) {
+            // if the option is positional only there is additional potential for ambiguities in config files and needs
+            // to be checked
+            std::string test_name = "--" + myopt.get_single_name();
+            if(test_name.size() == 3) {
+                test_name.erase(0, 1);
+            }
+
+            auto *op = get_option_no_throw(test_name);
+            if(op != nullptr) {
+                throw(OptionAlreadyAdded("added option positional name matches existing option: " + test_name));
+            }
+        } else if(parent_ != nullptr) {
+            for(auto &ln : myopt.lnames_) {
+                auto *op = parent_->get_option_no_throw(ln);
+                if(op != nullptr) {
+                    throw(OptionAlreadyAdded("added option matches existing positional option: " + ln));
+                }
+            }
+            for(auto &sn : myopt.snames_) {
+                auto *op = parent_->get_option_no_throw(sn);
+                if(op != nullptr) {
+                    throw(OptionAlreadyAdded("added option matches existing positional option: " + sn));
+                }
+            }
+        }
         options_.emplace_back();
         Option_p &option = options_.back();
         option.reset(new Option(option_name, option_description, option_callback, this));
@@ -7220,8 +8140,11 @@ CLI11_INLINE Option *App::set_config(std::string option_name,
         }
         if(!default_filename.empty()) {
             config_ptr_->default_str(std::move(default_filename));
+            config_ptr_->force_callback_ = true;
         }
         config_ptr_->configurable(false);
+        // set the option to take the last value and reverse given by default
+        config_ptr_->multi_option_policy(MultiOptionPolicy::Reverse);
     }
 
     return config_ptr_;
@@ -7251,13 +8174,14 @@ CLI11_INLINE bool App::remove_option(Option *opt) {
 CLI11_INLINE App *App::add_subcommand(std::string subcommand_name, std::string subcommand_description) {
     if(!subcommand_name.empty() && !detail::valid_name_string(subcommand_name)) {
         if(!detail::valid_first_char(subcommand_name[0])) {
-            throw IncorrectConstruction("Subcommand name starts with invalid character, '!' and '-' are not allowed");
+            throw IncorrectConstruction(
+                "Subcommand name starts with invalid character, '!' and '-' and control characters");
         }
         for(auto c : subcommand_name) {
             if(!detail::valid_later_char(c)) {
                 throw IncorrectConstruction(std::string("Subcommand name contains invalid character ('") + c +
                                             "'), all characters are allowed except"
-                                            "'=',':','{','}', and ' '");
+                                            "'=',':','{','}', ' ', and control characters");
             }
         }
     }
@@ -7382,17 +8306,29 @@ CLI11_INLINE void App::clear() {
     }
 }
 
-CLI11_INLINE void App::parse(int argc, const char *const *argv) {
+CLI11_INLINE void App::parse(int argc, const char *const *argv) { parse_char_t(argc, argv); }
+CLI11_INLINE void App::parse(int argc, const wchar_t *const *argv) { parse_char_t(argc, argv); }
+
+namespace detail {
+
+// Do nothing or perform narrowing
+CLI11_INLINE const char *maybe_narrow(const char *str) { return str; }
+CLI11_INLINE std::string maybe_narrow(const wchar_t *str) { return narrow(str); }
+
+}  // namespace detail
+
+template <class CharT> CLI11_INLINE void App::parse_char_t(int argc, const CharT *const *argv) {
     // If the name is not set, read from command line
     if(name_.empty() || has_automatic_name_) {
         has_automatic_name_ = true;
-        name_ = argv[0];
+        name_ = detail::maybe_narrow(argv[0]);
     }
 
     std::vector<std::string> args;
     args.reserve(static_cast<std::size_t>(argc) - 1U);
     for(auto i = static_cast<std::size_t>(argc) - 1U; i > 0U; --i)
-        args.emplace_back(argv[i]);
+        args.emplace_back(detail::maybe_narrow(argv[i]));
+
     parse(std::move(args));
 }
 
@@ -7418,11 +8354,19 @@ CLI11_INLINE void App::parse(std::string commandline, bool program_name_included
     auto args = detail::split_up(std::move(commandline));
     // remove all empty strings
     args.erase(std::remove(args.begin(), args.end(), std::string{}), args.end());
+    try {
+        detail::remove_quotes(args);
+    } catch(const std::invalid_argument &arg) {
+        throw CLI::ParseError(arg.what(), CLI::ExitCodes::InvalidError);
+    }
     std::reverse(args.begin(), args.end());
-
     parse(std::move(args));
 }
 
+CLI11_INLINE void App::parse(std::wstring commandline, bool program_name_included) {
+    parse(narrow(commandline), program_name_included);
+}
+
 CLI11_INLINE void App::parse(std::vector<std::string> &args) {
     // Clear if parsed
     if(parsed_ > 0)
@@ -7489,7 +8433,7 @@ CLI11_INLINE int App::exit(const Error &e, std::ostream &out, std::ostream &err)
     }
 
     if(e.get_name() == "CallForVersion") {
-        out << e.what() << std::endl;
+        out << e.what() << '\n';
         return e.get_exit_code();
     }
 
@@ -7585,7 +8529,8 @@ CLI11_NODISCARD CLI11_INLINE std::string App::help(std::string prev, AppFormatMo
 CLI11_NODISCARD CLI11_INLINE std::string App::version() const {
     std::string val;
     if(version_ptr_ != nullptr) {
-        auto rv = version_ptr_->results();
+        // copy the results for reuse later
+        results_t rv = version_ptr_->results();
         version_ptr_->clear();
         version_ptr_->add_result("true");
         try {
@@ -7694,7 +8639,7 @@ CLI11_NODISCARD CLI11_INLINE bool App::check_name(std::string name_to_check) con
     if(local_name == name_to_check) {
         return true;
     }
-    for(auto les : aliases_) {  // NOLINT(performance-for-range-copy)
+    for(std::string les : aliases_) {  // NOLINT(performance-for-range-copy)
         if(ignore_underscore_) {
             les = detail::remove_underscore(les);
         }
@@ -7884,70 +8829,96 @@ CLI11_NODISCARD CLI11_INLINE detail::Classifier App::_recognize(const std::strin
         return detail::Classifier::WINDOWS_STYLE;
     if((current == "++") && !name_.empty() && parent_ != nullptr)
         return detail::Classifier::SUBCOMMAND_TERMINATOR;
+    auto dotloc = current.find_first_of('.');
+    if(dotloc != std::string::npos) {
+        auto *cm = _find_subcommand(current.substr(0, dotloc), true, ignore_used_subcommands);
+        if(cm != nullptr) {
+            auto res = cm->_recognize(current.substr(dotloc + 1), ignore_used_subcommands);
+            if(res == detail::Classifier::SUBCOMMAND) {
+                return res;
+            }
+        }
+    }
     return detail::Classifier::NONE;
 }
 
+CLI11_INLINE bool App::_process_config_file(const std::string &config_file, bool throw_error) {
+    auto path_result = detail::check_path(config_file.c_str());
+    if(path_result == detail::path_type::file) {
+        try {
+            std::vector<ConfigItem> values = config_formatter_->from_file(config_file);
+            _parse_config(values);
+            return true;
+        } catch(const FileError &) {
+            if(throw_error) {
+                throw;
+            }
+            return false;
+        }
+    } else if(throw_error) {
+        throw FileError::Missing(config_file);
+    } else {
+        return false;
+    }
+}
+
 CLI11_INLINE void App::_process_config_file() {
     if(config_ptr_ != nullptr) {
         bool config_required = config_ptr_->get_required();
         auto file_given = config_ptr_->count() > 0;
+        if(!(file_given || config_ptr_->envname_.empty())) {
+            std::string ename_string = detail::get_environment_value(config_ptr_->envname_);
+            if(!ename_string.empty()) {
+                config_ptr_->add_result(ename_string);
+            }
+        }
+        config_ptr_->run_callback();
+
         auto config_files = config_ptr_->as<std::vector<std::string>>();
+        bool files_used{file_given};
         if(config_files.empty() || config_files.front().empty()) {
             if(config_required) {
-                throw FileError::Missing("no specified config file");
+                throw FileError("config file is required but none was given");
             }
             return;
         }
-        for(auto rit = config_files.rbegin(); rit != config_files.rend(); ++rit) {
-            const auto &config_file = *rit;
-            auto path_result = detail::check_path(config_file.c_str());
-            if(path_result == detail::path_type::file) {
-                try {
-                    std::vector<ConfigItem> values = config_formatter_->from_file(config_file);
-                    _parse_config(values);
-                    if(!file_given) {
-                        config_ptr_->add_result(config_file);
-                    }
-                } catch(const FileError &) {
-                    if(config_required || file_given)
-                        throw;
-                }
-            } else if(config_required || file_given) {
-                throw FileError::Missing(config_file);
+        for(const auto &config_file : config_files) {
+            if(_process_config_file(config_file, config_required || file_given)) {
+                files_used = true;
             }
         }
+        if(!files_used) {
+            // this is done so the count shows as 0 if no callbacks were processed
+            config_ptr_->clear();
+            bool force = config_ptr_->force_callback_;
+            config_ptr_->force_callback_ = false;
+            config_ptr_->run_callback();
+            config_ptr_->force_callback_ = force;
+        }
     }
 }
 
 CLI11_INLINE void App::_process_env() {
     for(const Option_p &opt : options_) {
         if(opt->count() == 0 && !opt->envname_.empty()) {
-            char *buffer = nullptr;
-            std::string ename_string;
-
-#ifdef _MSC_VER
-            // Windows version
-            std::size_t sz = 0;
-            if(_dupenv_s(&buffer, &sz, opt->envname_.c_str()) == 0 && buffer != nullptr) {
-                ename_string = std::string(buffer);
-                free(buffer);
-            }
-#else
-            // This also works on Windows, but gives a warning
-            buffer = std::getenv(opt->envname_.c_str());
-            if(buffer != nullptr)
-                ename_string = std::string(buffer);
-#endif
-
+            std::string ename_string = detail::get_environment_value(opt->envname_);
             if(!ename_string.empty()) {
-                opt->add_result(ename_string);
+                std::string result = ename_string;
+                result = opt->_validate(result, 0);
+                if(result.empty()) {
+                    opt->add_result(ename_string);
+                }
             }
         }
     }
 
     for(App_p &sub : subcommands_) {
-        if(sub->get_name().empty() || !sub->parse_complete_callback_)
-            sub->_process_env();
+        if(sub->get_name().empty() || !sub->parse_complete_callback_) {
+            if(sub->count_all() > 0) {
+                // only process environment variables if the callback has actually been triggered already
+                sub->_process_env();
+            }
+        }
     }
 }
 
@@ -8247,12 +9218,11 @@ CLI11_INLINE void App::_parse_config(const std::vector<ConfigItem> &args) {
 }
 
 CLI11_INLINE bool App::_parse_single_config(const ConfigItem &item, std::size_t level) {
+
     if(level < item.parents.size()) {
         try {
             auto *subcom = get_subcommand(item.parents.at(level));
-            auto result = subcom->_parse_single_config(item, level + 1);
-
-            return result;
+            return subcom->_parse_single_config(item, level + 1);
         } catch(const OptionNotFound &) {
             return false;
         }
@@ -8282,15 +9252,19 @@ CLI11_INLINE bool App::_parse_single_config(const ConfigItem &item, std::size_t
         if(item.name.size() == 1) {
             op = get_option_no_throw("-" + item.name);
         }
+        if(op == nullptr) {
+            op = get_option_no_throw(item.name);
+        }
     }
-    if(op == nullptr) {
-        op = get_option_no_throw(item.name);
-    }
+
     if(op == nullptr) {
         // If the option was not present
         if(get_allow_config_extras() == config_extras_mode::capture)
             // Should we worry about classifying the extras properly?
             missing_.emplace_back(detail::Classifier::NONE, item.fullname());
+        for(const auto &input : item.inputs) {
+            missing_.emplace_back(detail::Classifier::NONE, input);
+        }
         return false;
     }
 
@@ -8309,29 +9283,54 @@ CLI11_INLINE bool App::_parse_single_config(const ConfigItem &item, std::size_t
                 auto res = config_formatter_->to_flag(item);
                 bool converted{false};
                 if(op->get_disable_flag_override()) {
-
-                    try {
-                        auto val = detail::to_flag_value(res);
-                        if(val == 1) {
-                            res = op->get_flag_value(item.name, "{}");
-                            converted = true;
-                        }
-                    } catch(...) {
+                    auto val = detail::to_flag_value(res);
+                    if(val == 1) {
+                        res = op->get_flag_value(item.name, "{}");
+                        converted = true;
                     }
                 }
 
                 if(!converted) {
+                    errno = 0;
                     res = op->get_flag_value(item.name, res);
                 }
 
                 op->add_result(res);
                 return true;
             }
-            if(static_cast<int>(item.inputs.size()) > op->get_items_expected_max()) {
+            if(static_cast<int>(item.inputs.size()) > op->get_items_expected_max() &&
+               op->get_multi_option_policy() != MultiOptionPolicy::TakeAll) {
                 if(op->get_items_expected_max() > 1) {
                     throw ArgumentMismatch::AtMost(item.fullname(), op->get_items_expected_max(), item.inputs.size());
                 }
-                throw ConversionError::TooManyInputsFlag(item.fullname());
+
+                if(!op->get_disable_flag_override()) {
+                    throw ConversionError::TooManyInputsFlag(item.fullname());
+                }
+                // if the disable flag override is set then we must have the flag values match a known flag value
+                // this is true regardless of the output value, so an array input is possible and must be accounted for
+                for(const auto &res : item.inputs) {
+                    bool valid_value{false};
+                    if(op->default_flag_values_.empty()) {
+                        if(res == "true" || res == "false" || res == "1" || res == "0") {
+                            valid_value = true;
+                        }
+                    } else {
+                        for(const auto &valid_res : op->default_flag_values_) {
+                            if(valid_res.second == res) {
+                                valid_value = true;
+                                break;
+                            }
+                        }
+                    }
+
+                    if(valid_value) {
+                        op->add_result(res);
+                    } else {
+                        throw InvalidError("invalid flag argument given");
+                    }
+                }
+                return true;
             }
         }
         op->add_result(item.inputs);
@@ -8366,7 +9365,7 @@ CLI11_INLINE bool App::_parse_single(std::vector<std::string> &args, bool &posit
     case detail::Classifier::SHORT:
     case detail::Classifier::WINDOWS_STYLE:
         // If already parsed a subcommand, don't accept options_
-        _parse_arg(args, classifier);
+        retval = _parse_arg(args, classifier, false);
         break;
     case detail::Classifier::NONE:
         // Probably a positional or something for a parent (sub)command
@@ -8408,6 +9407,7 @@ CLI11_NODISCARD CLI11_INLINE bool App::_has_remaining_positionals() const {
 CLI11_INLINE bool App::_parse_positional(std::vector<std::string> &args, bool haltOnSubcommand) {
 
     const std::string &positional = args.back();
+    Option *posOpt{nullptr};
 
     if(positionals_at_end_) {
         // deal with the case of required arguments at the end which should take precedence over other arguments
@@ -8424,56 +9424,47 @@ CLI11_INLINE bool App::_parse_positional(std::vector<std::string> &args, bool ha
                                 continue;
                             }
                         }
-
-                        parse_order_.push_back(opt.get());
-                        /// if we require a separator add it here
-                        if(opt->get_inject_separator()) {
-                            if(!opt->results().empty() && !opt->results().back().empty()) {
-                                opt->add_result(std::string{});
-                            }
-                        }
-                        if(opt->get_trigger_on_parse() &&
-                           opt->current_option_state_ == Option::option_state::callback_run) {
-                            opt->clear();
-                        }
-                        opt->add_result(positional);
-                        if(opt->get_trigger_on_parse()) {
-                            opt->run_callback();
-                        }
-                        args.pop_back();
-                        return true;
+                        posOpt = opt.get();
+                        break;
                     }
                 }
             }
         }
     }
-    for(const Option_p &opt : options_) {
-        // Eat options, one by one, until done
-        if(opt->get_positional() &&
-           (static_cast<int>(opt->count()) < opt->get_items_expected_min() || opt->get_allow_extra_args())) {
-            if(validate_positionals_) {
-                std::string pos = positional;
-                pos = opt->_validate(pos, 0);
-                if(!pos.empty()) {
-                    continue;
-                }
-            }
-            if(opt->get_inject_separator()) {
-                if(!opt->results().empty() && !opt->results().back().empty()) {
-                    opt->add_result(std::string{});
+    if(posOpt == nullptr) {
+        for(const Option_p &opt : options_) {
+            // Eat options, one by one, until done
+            if(opt->get_positional() &&
+               (static_cast<int>(opt->count()) < opt->get_items_expected_min() || opt->get_allow_extra_args())) {
+                if(validate_positionals_) {
+                    std::string pos = positional;
+                    pos = opt->_validate(pos, 0);
+                    if(!pos.empty()) {
+                        continue;
+                    }
                 }
+                posOpt = opt.get();
+                break;
             }
-            if(opt->get_trigger_on_parse() && opt->current_option_state_ == Option::option_state::callback_run) {
-                opt->clear();
-            }
-            opt->add_result(positional);
-            if(opt->get_trigger_on_parse()) {
-                opt->run_callback();
+        }
+    }
+    if(posOpt != nullptr) {
+        parse_order_.push_back(posOpt);
+        if(posOpt->get_inject_separator()) {
+            if(!posOpt->results().empty() && !posOpt->results().back().empty()) {
+                posOpt->add_result(std::string{});
             }
-            parse_order_.push_back(opt.get());
-            args.pop_back();
-            return true;
         }
+        if(posOpt->get_trigger_on_parse() && posOpt->current_option_state_ == Option::option_state::callback_run) {
+            posOpt->clear();
+        }
+        posOpt->add_result(positional);
+        if(posOpt->get_trigger_on_parse()) {
+            posOpt->run_callback();
+        }
+
+        args.pop_back();
+        return true;
     }
 
     for(auto &subc : subcommands_) {
@@ -8554,6 +9545,17 @@ CLI11_INLINE bool App::_parse_subcommand(std::vector<std::string> &args) {
         return true;
     }
     auto *com = _find_subcommand(args.back(), true, true);
+    if(com == nullptr) {
+        // the main way to get here is using .notation
+        auto dotloc = args.back().find_first_of('.');
+        if(dotloc != std::string::npos) {
+            com = _find_subcommand(args.back().substr(0, dotloc), true, true);
+            if(com != nullptr) {
+                args.back() = args.back().substr(dotloc + 1);
+                args.push_back(com->get_display_name());
+            }
+        }
+    }
     if(com != nullptr) {
         args.pop_back();
         if(!com->silent_) {
@@ -8576,7 +9578,8 @@ CLI11_INLINE bool App::_parse_subcommand(std::vector<std::string> &args) {
     return false;
 }
 
-CLI11_INLINE bool App::_parse_arg(std::vector<std::string> &args, detail::Classifier current_type) {
+CLI11_INLINE bool
+App::_parse_arg(std::vector<std::string> &args, detail::Classifier current_type, bool local_processing_only) {
 
     std::string current = args.back();
 
@@ -8618,7 +9621,7 @@ CLI11_INLINE bool App::_parse_arg(std::vector<std::string> &args, detail::Classi
     if(op_ptr == std::end(options_)) {
         for(auto &subc : subcommands_) {
             if(subc->name_.empty() && !subc->disabled_) {
-                if(subc->_parse_arg(args, current_type)) {
+                if(subc->_parse_arg(args, current_type, local_processing_only)) {
                     if(!subc->pre_parse_called_) {
                         subc->_trigger_pre_parse(args.size());
                     }
@@ -8632,9 +9635,57 @@ CLI11_INLINE bool App::_parse_arg(std::vector<std::string> &args, detail::Classi
             return false;
         }
 
+        // now check for '.' notation of subcommands
+        auto dotloc = arg_name.find_first_of('.', 1);
+        if(dotloc != std::string::npos) {
+            // using dot notation is equivalent to single argument subcommand
+            auto *sub = _find_subcommand(arg_name.substr(0, dotloc), true, false);
+            if(sub != nullptr) {
+                auto v = args.back();
+                args.pop_back();
+                arg_name = arg_name.substr(dotloc + 1);
+                if(arg_name.size() > 1) {
+                    args.push_back(std::string("--") + v.substr(dotloc + 3));
+                    current_type = detail::Classifier::LONG;
+                } else {
+                    auto nval = v.substr(dotloc + 2);
+                    nval.front() = '-';
+                    if(nval.size() > 2) {
+                        // '=' not allowed in short form arguments
+                        args.push_back(nval.substr(3));
+                        nval.resize(2);
+                    }
+                    args.push_back(nval);
+                    current_type = detail::Classifier::SHORT;
+                }
+                auto val = sub->_parse_arg(args, current_type, true);
+                if(val) {
+                    if(!sub->silent_) {
+                        parsed_subcommands_.push_back(sub);
+                    }
+                    // deal with preparsing
+                    increment_parsed();
+                    _trigger_pre_parse(args.size());
+                    // run the parse complete callback since the subcommand processing is now complete
+                    if(sub->parse_complete_callback_) {
+                        sub->_process_env();
+                        sub->_process_callbacks();
+                        sub->_process_help_flags();
+                        sub->_process_requirements();
+                        sub->run_callback(false, true);
+                    }
+                    return true;
+                }
+                args.pop_back();
+                args.push_back(v);
+            }
+        }
+        if(local_processing_only) {
+            return false;
+        }
         // If a subcommand, try the main command
         if(parent_ != nullptr && fallthrough_)
-            return _get_fallthrough_parent()->_parse_arg(args, current_type);
+            return _get_fallthrough_parent()->_parse_arg(args, current_type, false);
 
         // Otherwise, add to missing
         args.pop_back();
@@ -8756,7 +9807,7 @@ CLI11_INLINE void App::_trigger_pre_parse(std::size_t remaining_args) {
     } else if(immediate_callback_) {
         if(!name_.empty()) {
             auto pcnt = parsed_;
-            auto extras = std::move(missing_);
+            missing_t extras = std::move(missing_);
             clear();
             parsed_ = pcnt;
             pre_parse_called_ = true;
@@ -8942,12 +9993,12 @@ CLI11_INLINE void retire_option(App *app, Option *opt) {
                             ->allow_extra_args(opt->get_allow_extra_args());
 
     app->remove_option(opt);
-    auto *opt2 = app->add_option(option_copy->get_name(false, true), "option has been retired and has no effect")
-                     ->type_name("RETIRED")
-                     ->default_str("RETIRED")
-                     ->type_size(option_copy->get_type_size_min(), option_copy->get_type_size_max())
-                     ->expected(option_copy->get_expected_min(), option_copy->get_expected_max())
-                     ->allow_extra_args(option_copy->get_allow_extra_args());
+    auto *opt2 = app->add_option(option_copy->get_name(false, true), "option has been retired and has no effect");
+    opt2->type_name("RETIRED")
+        ->default_str("RETIRED")
+        ->type_size(option_copy->get_type_size_min(), option_copy->get_type_size_max())
+        ->expected(option_copy->get_expected_min(), option_copy->get_expected_max())
+        ->allow_extra_args(option_copy->get_allow_extra_args());
 
     Validator retired_warning{[opt2](std::string &) {
                                   std::cout << "WARNING " << opt2->get_name() << " is retired and has no effect\n";
@@ -9015,7 +10066,10 @@ CLI11_INLINE std::string help(const App *app, const Error &e) {
 
 namespace detail {
 
-std::string convert_arg_for_ini(const std::string &arg, char stringQuote = '"', char characterQuote = '\'');
+std::string convert_arg_for_ini(const std::string &arg,
+                                char stringQuote = '"',
+                                char literalQuote = '\'',
+                                bool disable_multi_line = false);
 
 /// Comma separated join, adds quotes if needed
 std::string ini_join(const std::vector<std::string> &args,
@@ -9023,7 +10077,9 @@ std::string ini_join(const std::vector<std::string> &args,
                      char arrayStart = '[',
                      char arrayEnd = ']',
                      char stringQuote = '"',
-                     char characterQuote = '\'');
+                     char literalQuote = '\'');
+
+void clean_name_string(std::string &name, const std::string &keyChars);
 
 std::vector<std::string> generate_parents(const std::string &section, std::string &name, char parentSeparator);
 
@@ -9034,9 +10090,19 @@ void checkParentSegments(std::vector<ConfigItem> &output, const std::string &cur
 
 
 
+static constexpr auto multiline_literal_quote = R"(''')";
+static constexpr auto multiline_string_quote = R"(""")";
+
 namespace detail {
 
-CLI11_INLINE std::string convert_arg_for_ini(const std::string &arg, char stringQuote, char characterQuote) {
+CLI11_INLINE bool is_printable(const std::string &test_string) {
+    return std::all_of(test_string.begin(), test_string.end(), [](char x) {
+        return (isprint(static_cast<unsigned char>(x)) != 0 || x == '\n' || x == '\t');
+    });
+}
+
+CLI11_INLINE std::string
+convert_arg_for_ini(const std::string &arg, char stringQuote, char literalQuote, bool disable_multi_line) {
     if(arg.empty()) {
         return std::string(2, stringQuote);
     }
@@ -9049,12 +10115,20 @@ CLI11_INLINE std::string convert_arg_for_ini(const std::string &arg, char string
         using CLI::detail::lexical_cast;
         double val = 0.0;
         if(lexical_cast(arg, val)) {
-            return arg;
+            if(arg.find_first_not_of("0123456789.-+eE") == std::string::npos) {
+                return arg;
+            }
         }
     }
     // just quote a single non numeric character
     if(arg.size() == 1) {
-        return std::string(1, characterQuote) + arg + characterQuote;
+        if(isprint(static_cast<unsigned char>(arg.front())) == 0) {
+            return binary_escape_string(arg);
+        }
+        if(arg == "'") {
+            return std::string(1, stringQuote) + "'" + stringQuote;
+        }
+        return std::string(1, literalQuote) + arg + literalQuote;
     }
     // handle hex, binary or octal arguments
     if(arg.front() == '0') {
@@ -9074,10 +10148,16 @@ CLI11_INLINE std::string convert_arg_for_ini(const std::string &arg, char string
             }
         }
     }
-    if(arg.find_first_of(stringQuote) == std::string::npos) {
-        return std::string(1, stringQuote) + arg + stringQuote;
+    if(!is_printable(arg)) {
+        return binary_escape_string(arg);
     }
-    return characterQuote + arg + characterQuote;
+    if(detail::has_escapable_character(arg)) {
+        if(arg.size() > 100 && !disable_multi_line) {
+            return std::string(multiline_literal_quote) + arg + multiline_literal_quote;
+        }
+        return std::string(1, stringQuote) + detail::add_escaped_characters(arg) + stringQuote;
+    }
+    return std::string(1, stringQuote) + arg + stringQuote;
 }
 
 CLI11_INLINE std::string ini_join(const std::vector<std::string> &args,
@@ -9085,10 +10165,12 @@ CLI11_INLINE std::string ini_join(const std::vector<std::string> &args,
                                   char arrayStart,
                                   char arrayEnd,
                                   char stringQuote,
-                                  char characterQuote) {
+                                  char literalQuote) {
+    bool disable_multi_line{false};
     std::string joined;
     if(args.size() > 1 && arrayStart != '\0') {
         joined.push_back(arrayStart);
+        disable_multi_line = true;
     }
     std::size_t start = 0;
     for(const auto &arg : args) {
@@ -9098,7 +10180,7 @@ CLI11_INLINE std::string ini_join(const std::vector<std::string> &args,
                 joined.push_back(' ');
             }
         }
-        joined.append(convert_arg_for_ini(arg, stringQuote, characterQuote));
+        joined.append(convert_arg_for_ini(arg, stringQuote, literalQuote, disable_multi_line));
     }
     if(args.size() > 1 && arrayEnd != '\0') {
         joined.push_back(arrayEnd);
@@ -9111,22 +10193,22 @@ generate_parents(const std::string &section, std::string &name, char parentSepar
     std::vector<std::string> parents;
     if(detail::to_lower(section) != "default") {
         if(section.find(parentSeparator) != std::string::npos) {
-            parents = detail::split(section, parentSeparator);
+            parents = detail::split_up(section, parentSeparator);
         } else {
             parents = {section};
         }
     }
     if(name.find(parentSeparator) != std::string::npos) {
-        std::vector<std::string> plist = detail::split(name, parentSeparator);
+        std::vector<std::string> plist = detail::split_up(name, parentSeparator);
         name = plist.back();
-        detail::remove_quotes(name);
         plist.pop_back();
         parents.insert(parents.end(), plist.begin(), plist.end());
     }
-
     // clean up quotes on the parents
-    for(auto &parent : parents) {
-        detail::remove_quotes(parent);
+    try {
+        detail::remove_quotes(parents);
+    } catch(const std::invalid_argument &iarg) {
+        throw CLI::ParseError(iarg.what(), CLI::ExitCodes::InvalidError);
     }
     return parents;
 }
@@ -9179,30 +10261,59 @@ checkParentSegments(std::vector<ConfigItem> &output, const std::string &currentS
     output.back().parents = std::move(parents);
     output.back().name = "++";
 }
+
+/// @brief  checks if a string represents a multiline comment
+CLI11_INLINE bool hasMLString(std::string const &fullString, char check) {
+    if(fullString.length() < 3) {
+        return false;
+    }
+    auto it = fullString.rbegin();
+    return (*it == check) && (*(it + 1) == check) && (*(it + 2) == check);
+}
 }  // namespace detail
 
 inline std::vector<ConfigItem> ConfigBase::from_config(std::istream &input) const {
     std::string line;
+    std::string buffer;
     std::string currentSection = "default";
     std::string previousSection = "default";
     std::vector<ConfigItem> output;
     bool isDefaultArray = (arrayStart == '[' && arrayEnd == ']' && arraySeparator == ',');
     bool isINIArray = (arrayStart == '\0' || arrayStart == ' ') && arrayStart == arrayEnd;
     bool inSection{false};
+    bool inMLineComment{false};
+    bool inMLineValue{false};
+
     char aStart = (isINIArray) ? '[' : arrayStart;
     char aEnd = (isINIArray) ? ']' : arrayEnd;
     char aSep = (isINIArray && arraySeparator == ' ') ? ',' : arraySeparator;
     int currentSectionIndex{0};
-    while(getline(input, line)) {
+
+    std::string line_sep_chars{parentSeparatorChar, commentChar, valueDelimiter};
+    while(getline(input, buffer)) {
         std::vector<std::string> items_buffer;
         std::string name;
-
-        detail::trim(line);
+        line = detail::trim_copy(buffer);
         std::size_t len = line.length();
         // lines have to be at least 3 characters to have any meaning to CLI just skip the rest
         if(len < 3) {
             continue;
         }
+        if(line.compare(0, 3, multiline_string_quote) == 0 || line.compare(0, 3, multiline_literal_quote) == 0) {
+            inMLineComment = true;
+            auto cchar = line.front();
+            while(inMLineComment) {
+                if(getline(input, line)) {
+                    detail::trim(line);
+                } else {
+                    break;
+                }
+                if(detail::hasMLString(line, cchar)) {
+                    inMLineComment = false;
+                }
+            }
+            continue;
+        }
         if(line.front() == '[' && line.back() == ']') {
             if(currentSection != "default") {
                 // insert a section end which is just an empty items_buffer
@@ -9234,49 +10345,130 @@ inline std::vector<ConfigItem> ConfigBase::from_config(std::istream &input) cons
         if(line.front() == ';' || line.front() == '#' || line.front() == commentChar) {
             continue;
         }
-
+        std::size_t search_start = 0;
+        if(line.find_first_of("\"'`") != std::string::npos) {
+            while(search_start < line.size()) {
+                auto test_char = line[search_start];
+                if(test_char == '\"' || test_char == '\'' || test_char == '`') {
+                    search_start = detail::close_sequence(line, search_start, line[search_start]);
+                    ++search_start;
+                } else if(test_char == valueDelimiter || test_char == commentChar) {
+                    --search_start;
+                    break;
+                } else if(test_char == ' ' || test_char == '\t' || test_char == parentSeparatorChar) {
+                    ++search_start;
+                } else {
+                    search_start = line.find_first_of(line_sep_chars, search_start);
+                }
+            }
+        }
         // Find = in string, split and recombine
-        auto pos = line.find(valueDelimiter);
-        if(pos != std::string::npos) {
-            name = detail::trim_copy(line.substr(0, pos));
-            std::string item = detail::trim_copy(line.substr(pos + 1));
-            auto cloc = item.find(commentChar);
-            if(cloc != std::string::npos) {
-                item.erase(cloc, std::string::npos);  // NOLINT(readability-suspicious-call-argument)
-                detail::trim(item);
-            }
-            if(item.size() > 1 && item.front() == aStart) {
+        auto delimiter_pos = line.find_first_of(valueDelimiter, search_start + 1);
+        auto comment_pos = line.find_first_of(commentChar, search_start);
+        if(comment_pos < delimiter_pos) {
+            delimiter_pos = std::string::npos;
+        }
+        if(delimiter_pos != std::string::npos) {
+
+            name = detail::trim_copy(line.substr(0, delimiter_pos));
+            std::string item = detail::trim_copy(line.substr(delimiter_pos + 1, std::string::npos));
+            bool mlquote =
+                (item.compare(0, 3, multiline_literal_quote) == 0 || item.compare(0, 3, multiline_string_quote) == 0);
+            if(!mlquote && comment_pos != std::string::npos) {
+                auto citems = detail::split_up(item, commentChar);
+                item = detail::trim_copy(citems.front());
+            }
+            if(mlquote) {
+                // mutliline string
+                auto keyChar = item.front();
+                item = buffer.substr(delimiter_pos + 1, std::string::npos);
+                detail::ltrim(item);
+                item.erase(0, 3);
+                inMLineValue = true;
+                bool lineExtension{false};
+                bool firstLine = true;
+                if(!item.empty() && item.back() == '\\') {
+                    item.pop_back();
+                    lineExtension = true;
+                }
+                while(inMLineValue) {
+                    std::string l2;
+                    if(!std::getline(input, l2)) {
+                        break;
+                    }
+                    line = l2;
+                    detail::rtrim(line);
+                    if(detail::hasMLString(line, keyChar)) {
+                        line.pop_back();
+                        line.pop_back();
+                        line.pop_back();
+                        if(lineExtension) {
+                            detail::ltrim(line);
+                        } else if(!(firstLine && item.empty())) {
+                            item.push_back('\n');
+                        }
+                        firstLine = false;
+                        item += line;
+                        inMLineValue = false;
+                        if(!item.empty() && item.back() == '\n') {
+                            item.pop_back();
+                        }
+                        if(keyChar == '\"') {
+                            try {
+                                item = detail::remove_escaped_characters(item);
+                            } catch(const std::invalid_argument &iarg) {
+                                throw CLI::ParseError(iarg.what(), CLI::ExitCodes::InvalidError);
+                            }
+                        }
+                    } else {
+                        if(lineExtension) {
+                            detail::trim(l2);
+                        } else if(!(firstLine && item.empty())) {
+                            item.push_back('\n');
+                        }
+                        lineExtension = false;
+                        firstLine = false;
+                        if(!l2.empty() && l2.back() == '\\') {
+                            lineExtension = true;
+                            l2.pop_back();
+                        }
+                        item += l2;
+                    }
+                }
+                items_buffer = {item};
+            } else if(item.size() > 1 && item.front() == aStart) {
                 for(std::string multiline; item.back() != aEnd && std::getline(input, multiline);) {
                     detail::trim(multiline);
                     item += multiline;
                 }
-                items_buffer = detail::split_up(item.substr(1, item.length() - 2), aSep);
+                if(item.back() == aEnd) {
+                    items_buffer = detail::split_up(item.substr(1, item.length() - 2), aSep);
+                } else {
+                    items_buffer = detail::split_up(item.substr(1, std::string::npos), aSep);
+                }
             } else if((isDefaultArray || isINIArray) && item.find_first_of(aSep) != std::string::npos) {
                 items_buffer = detail::split_up(item, aSep);
             } else if((isDefaultArray || isINIArray) && item.find_first_of(' ') != std::string::npos) {
-                items_buffer = detail::split_up(item);
+                items_buffer = detail::split_up(item, '\0');
             } else {
                 items_buffer = {item};
             }
         } else {
-            name = detail::trim_copy(line);
-            auto cloc = name.find(commentChar);
-            if(cloc != std::string::npos) {
-                name.erase(cloc, std::string::npos);  // NOLINT(readability-suspicious-call-argument)
-                detail::trim(name);
-            }
-
+            name = detail::trim_copy(line.substr(0, comment_pos));
             items_buffer = {"true"};
         }
-        if(name.find(parentSeparatorChar) == std::string::npos) {
-            detail::remove_quotes(name);
-        }
-        // clean up quotes on the items
-        for(auto &it : items_buffer) {
-            detail::remove_quotes(it);
+        std::vector<std::string> parents;
+        try {
+            parents = detail::generate_parents(currentSection, name, parentSeparatorChar);
+            detail::process_quoted_string(name);
+            // clean up quotes on the items and check for escaped strings
+            for(auto &it : items_buffer) {
+                detail::process_quoted_string(it, stringQuote, literalQuote);
+            }
+        } catch(const std::invalid_argument &ia) {
+            throw CLI::ParseError(ia.what(), CLI::ExitCodes::InvalidError);
         }
 
-        std::vector<std::string> parents = detail::generate_parents(currentSection, name, parentSeparatorChar);
         if(parents.size() > maximumLayers) {
             continue;
         }
@@ -9313,6 +10505,23 @@ inline std::vector<ConfigItem> ConfigBase::from_config(std::istream &input) cons
     return output;
 }
 
+CLI11_INLINE std::string &clean_name_string(std::string &name, const std::string &keyChars) {
+    if(name.find_first_of(keyChars) != std::string::npos || (name.front() == '[' && name.back() == ']') ||
+       (name.find_first_of("'`\"\\") != std::string::npos)) {
+        if(name.find_first_of('\'') == std::string::npos) {
+            name.insert(0, 1, '\'');
+            name.push_back('\'');
+        } else {
+            if(detail::has_escapable_character(name)) {
+                name = detail::add_escaped_characters(name);
+            }
+            name.insert(0, 1, '\"');
+            name.push_back('\"');
+        }
+    }
+    return name;
+}
+
 CLI11_INLINE std::string
 ConfigBase::to_config(const App *app, bool default_also, bool write_description, std::string prefix) const {
     std::stringstream out;
@@ -9320,6 +10529,18 @@ ConfigBase::to_config(const App *app, bool default_also, bool write_description,
     commentLead.push_back(commentChar);
     commentLead.push_back(' ');
 
+    std::string commentTest = "#;";
+    commentTest.push_back(commentChar);
+    commentTest.push_back(parentSeparatorChar);
+
+    std::string keyChars = commentTest;
+    keyChars.push_back(literalQuote);
+    keyChars.push_back(stringQuote);
+    keyChars.push_back(arrayStart);
+    keyChars.push_back(arrayEnd);
+    keyChars.push_back(valueDelimiter);
+    keyChars.push_back(arraySeparator);
+
     std::vector<std::string> groups = app->get_groups();
     bool defaultUsed = false;
     groups.insert(groups.begin(), std::string("Options"));
@@ -9345,13 +10566,17 @@ ConfigBase::to_config(const App *app, bool default_also, bool write_description,
                         continue;
                     }
                 }
-                std::string name = prefix + opt->get_single_name();
+                std::string single_name = opt->get_single_name();
+                if(single_name.empty()) {
+                    continue;
+                }
+
                 std::string value = detail::ini_join(
-                    opt->reduced_results(), arraySeparator, arrayStart, arrayEnd, stringQuote, characterQuote);
+                    opt->reduced_results(), arraySeparator, arrayStart, arrayEnd, stringQuote, literalQuote);
 
                 if(value.empty() && default_also) {
                     if(!opt->get_default_str().empty()) {
-                        value = detail::convert_arg_for_ini(opt->get_default_str(), stringQuote, characterQuote);
+                        value = detail::convert_arg_for_ini(opt->get_default_str(), stringQuote, literalQuote, false);
                     } else if(opt->get_expected_min() == 0) {
                         value = "false";
                     } else if(opt->get_run_callback_for_default()) {
@@ -9360,13 +10585,35 @@ ConfigBase::to_config(const App *app, bool default_also, bool write_description,
                 }
 
                 if(!value.empty()) {
+
                     if(!opt->get_fnames().empty()) {
-                        value = opt->get_flag_value(name, value);
+                        try {
+                            value = opt->get_flag_value(single_name, value);
+                        } catch(const CLI::ArgumentMismatch &) {
+                            bool valid{false};
+                            for(const auto &test_name : opt->get_fnames()) {
+                                try {
+                                    value = opt->get_flag_value(test_name, value);
+                                    single_name = test_name;
+                                    valid = true;
+                                } catch(const CLI::ArgumentMismatch &) {
+                                    continue;
+                                }
+                            }
+                            if(!valid) {
+                                value = detail::ini_join(
+                                    opt->results(), arraySeparator, arrayStart, arrayEnd, stringQuote, literalQuote);
+                            }
+                        }
                     }
                     if(write_description && opt->has_description()) {
                         out << '\n';
                         out << commentLead << detail::fix_newlines(commentLead, opt->get_description()) << '\n';
                     }
+                    clean_name_string(single_name, keyChars);
+
+                    std::string name = prefix + single_name;
+
                     out << name << valueDelimiter << value << '\n';
                 }
             }
@@ -9375,31 +10622,56 @@ ConfigBase::to_config(const App *app, bool default_also, bool write_description,
     auto subcommands = app->get_subcommands({});
     for(const App *subcom : subcommands) {
         if(subcom->get_name().empty()) {
+            if(!default_also && (subcom->count_all() == 0)) {
+                continue;
+            }
             if(write_description && !subcom->get_group().empty()) {
                 out << '\n' << commentLead << subcom->get_group() << " Options\n";
             }
+            /*if (!prefix.empty() || app->get_parent() == nullptr) {
+                out << '[' << prefix << "___"<< subcom->get_group() << "]\n";
+            } else {
+                std::string subname = app->get_name() + parentSeparatorChar + "___"+subcom->get_group();
+                const auto *p = app->get_parent();
+                while(p->get_parent() != nullptr) {
+                    subname = p->get_name() + parentSeparatorChar +subname;
+                    p = p->get_parent();
+                }
+                out << '[' << subname << "]\n";
+            }
+            */
             out << to_config(subcom, default_also, write_description, prefix);
         }
     }
 
     for(const App *subcom : subcommands) {
         if(!subcom->get_name().empty()) {
+            if(!default_also && (subcom->count_all() == 0)) {
+                continue;
+            }
+            std::string subname = subcom->get_name();
+            clean_name_string(subname, keyChars);
+
             if(subcom->get_configurable() && app->got_subcommand(subcom)) {
                 if(!prefix.empty() || app->get_parent() == nullptr) {
-                    out << '[' << prefix << subcom->get_name() << "]\n";
+
+                    out << '[' << prefix << subname << "]\n";
                 } else {
-                    std::string subname = app->get_name() + parentSeparatorChar + subcom->get_name();
+                    std::string appname = app->get_name();
+                    clean_name_string(appname, keyChars);
+                    subname = appname + parentSeparatorChar + subname;
                     const auto *p = app->get_parent();
                     while(p->get_parent() != nullptr) {
-                        subname = p->get_name() + parentSeparatorChar + subname;
+                        std::string pname = p->get_name();
+                        clean_name_string(pname, keyChars);
+                        subname = pname + parentSeparatorChar + subname;
                         p = p->get_parent();
                     }
                     out << '[' << subname << "]\n";
                 }
                 out << to_config(subcom, default_also, write_description, "");
             } else {
-                out << to_config(
-                    subcom, default_also, write_description, prefix + subcom->get_name() + parentSeparatorChar);
+                out << to_config(subcom, default_also, write_description, prefix + subname + parentSeparatorChar);
             }
         }
     }
@@ -9463,7 +10735,7 @@ CLI11_INLINE std::string Formatter::make_description(const App *app) const {
     auto min_options = app->get_require_option_min();
     auto max_options = app->get_require_option_max();
     if(app->get_required()) {
-        desc += " REQUIRED ";
+        desc += " " + get_label("REQUIRED") + " ";
     }
     if((max_options == min_options) && (min_options > 0)) {
         if(min_options == 1) {
@@ -9485,6 +10757,11 @@ CLI11_INLINE std::string Formatter::make_description(const App *app) const {
 }
 
 CLI11_INLINE std::string Formatter::make_usage(const App *app, std::string name) const {
+    std::string usage = app->get_usage();
+    if(!usage.empty()) {
+        return usage + "\n";
+    }
+
     std::stringstream out;
 
     out << get_label("Usage") << ":" << (name.empty() ? "" : " ") << name;
@@ -9521,7 +10798,7 @@ CLI11_INLINE std::string Formatter::make_usage(const App *app, std::string name)
             << (app->get_require_subcommand_min() == 0 ? "]" : "");
     }
 
-    out << std::endl;
+    out << '\n';
 
     return out.str();
 }
@@ -9602,7 +10879,10 @@ CLI11_INLINE std::string Formatter::make_subcommands(const App *app, AppFormatMo
 
 CLI11_INLINE std::string Formatter::make_subcommand(const App *sub) const {
     std::stringstream out;
-    detail::format_help(out, sub->get_display_name(true), sub->get_description(), column_width_);
+    detail::format_help(out,
+                        sub->get_display_name(true) + (sub->get_required() ? " " + get_label("REQUIRED") : ""),
+                        sub->get_description(),
+                        column_width_);
     return out.str();
 }