fix: parse special floating point values (#499)

* Avoid undefined std::abs(INT_MIN) in integer_parser

When parsing a negative integer into a signed type whose minimum value
equals INTMAX_MIN (e.g. int64_t on typical platforms), integer_parser
computes the limit as std::abs(static_cast<intmax_t>(min())). Negating
INTMAX_MIN cannot be represented in intmax_t, so the std::abs call is
undefined behaviour. UBSan flags this on every negative int64_t parse,
including a trivial one like "-1":

  runtime error: negation of -9223372036854775808 cannot be represented
  in type 'long'; cast to an unsigned type to negate this value to itself

Build the same unsigned magnitude (|min| == max + 1 for two's-complement)
directly in the unsigned arithmetic type instead. For unsigned T the
expression wraps to 0, which matches the previous std::abs(0) value, so
behaviour for unsigned types is preserved.

* test: cover INT64_MIN parse and run parser tests under UBSan

* test: skip UBSan flags on Windows clang-cl/MinGW builds

.clang-format

@@ -0,0 +1,19 @@
+---
+Language:        Cpp
+BasedOnStyle:  LLVM
+AccessModifierOffset: 0
+AlignConsecutiveAssignments: true
+AlwaysBreakAfterReturnType: TopLevel
+BreakBeforeBraces: Custom
+BraceWrapping:
+  AfterEnum: true
+  AfterClass: true
+  AfterStruct: true
+  AfterFunction: true
+  AfterNamespace: true
+  AfterControlStatement: Always
+  BeforeElse: true
+ConstructorInitializerIndentWidth: 2
+ContinuationIndentWidth: 2
+PenaltyReturnTypeOnItsOwnLine: 200
+PointerAlignment: Left

.github/workflows/build.yml

@@ -0,0 +1,24 @@
+name: Build cxxopts
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+  workflow_dispatch:
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: setup
+      run: mkdir build
+    - name: cmake
+      run: cd build; cmake ..
+    - name: Build
+      run: cd build; make -j$(nproc)
+    - name: test
+      run: cd build; ctest

.github/workflows/cifuzz.yml

@@ -0,0 +1,24 @@
+name: CIFuzz
+on: [pull_request]
+jobs:
+ Fuzzing:
+   runs-on: ubuntu-latest
+   steps:
+   - name: Build Fuzzers
+     id: build
+     uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
+     with:
+       oss-fuzz-project-name: 'cxxopts'
+       language: c++
+   - name: Run Fuzzers
+     uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
+     with:
+       oss-fuzz-project-name: 'cxxopts'
+       language: c++
+       fuzz-seconds: 300
+   - name: Upload Crash
+     uses: actions/upload-artifact@v4
+     if: failure() && steps.build.outcome == 'success'
+     with:
+       name: artifacts
+       path: ./out/artifacts

.github/workflows/cmake.yml

@@ -0,0 +1,75 @@
+name: CMake
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+  workflow_dispatch:
+
+env:
+  # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)
+  BUILD_TYPE: Release
+
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  build-ubuntu:
+    strategy:
+      matrix:
+        os: [ ubuntu-22.04, ubuntu-24.04 ]
+        compiler: [ g++-9, g++-10, clang++ ]
+
+    name: Build and Test on Ubuntu
+    runs-on: ${{matrix.os}}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup g++-9 if not exists
+        if: matrix.compiler == 'g++-9'
+        run: which g++-9 || (sudo apt-get update && sudo apt-get -y install g++-9)
+      - name: Setup g++10 if not exists
+        if: matrix.compiler == 'g++-10'
+        run: which g++10 || (sudo apt-get update && sudo apt-get -y install g++-10)
+      - name: Configure CMake
+        run: cmake -S "${{github.workspace}}" -B "${{github.workspace}}/build" -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DCMAKE_CXX_COMPILER=${{matrix.compiler}}
+      - name: Build
+        run: cmake --build "${{github.workspace}}/build" --config $BUILD_TYPE
+      - name: Test
+        working-directory: ${{github.workspace}}/build/test
+        run: ctest -C $BUILD_TYPE --output-on-failure
+
+  build-macos:
+    name: Build and Test on MacOS
+    strategy:
+      matrix:
+        os: [macos-latest]
+    runs-on: ${{matrix.os}}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Configure CMake
+        run: cmake -S "${{github.workspace}}" -B "${{github.workspace}}/build" -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+      - name: Show compile commands
+        run: cat build/compile_commands.json
+      - name: Build
+        run: cmake --build "${{github.workspace}}/build" --config $BUILD_TYPE
+      - name: Test
+        working-directory: ${{github.workspace}}/build/test
+        shell: bash
+        run: ctest -C $BUILD_TYPE --output-on-failure
+
+  build-windows:
+    name: Build and Test on Windows
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ilammy/msvc-dev-cmd@v1
+      - name: Configure CMake
+        run: cmake -S "${{github.workspace}}" -B "${{github.workspace}}/build" -DCMAKE_BUILD_TYPE=$BUILD_TYPE -T "ClangCl"
+      - name: Build
+        run: cmake --build "${{github.workspace}}/build" --config $BUILD_TYPE
+      - name: Test
+        working-directory: ${{github.workspace}}/build/test
+        run: cd $BUILD_TYPE && ./link_test && ./options_test

.github/workflows/meson.yml

@@ -0,0 +1,59 @@
+name: Meson
+
+on:
+  push:
+    branches: [ master, main ]
+  pull_request:
+    branches: [ master, main ]
+  workflow_dispatch:
+
+jobs:
+  build-ubuntu:
+    strategy:
+      matrix:
+        icu: [enabled, disabled]
+    name: Build and Test on Ubuntu
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-python@v5
+      - uses: BSFishy/meson-build@v1.0.3
+        with:
+          action: build
+          setup-options: -Dicu=${{ matrix.icu }}
+          meson-version: 0.64.1
+          directory: builddir
+      - name: Run Tests
+        run: meson test -C builddir
+      - name: Run examples
+        run: builddir/example
+
+  build-macos:
+    name: Build and Test on MacOS
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-python@v5
+      - uses: BSFishy/meson-build@v1.0.3
+        with:
+          action: build
+          meson-version: 1.10.0
+          directory: builddir
+      - name: Run Tests
+        run: meson test -C builddir
+
+  build-windows:
+    name: Build and Test on Windows
+    runs-on: windows-latest
+    steps:
+      - uses: ilammy/msvc-dev-cmd@v1
+      - uses: actions/checkout@v6
+      - uses: actions/setup-python@v5
+      - uses: BSFishy/meson-build@v1.0.3
+        with:
+          action: test
+          setup-options: -Dcpp_std=c++14  # MSVC doesn't actually support C++11, hide the warning
+          meson-version: 0.64.1
+          directory: builddir
+      - name: Run Tests
+        run: meson test -C builddir

.gitignore

@@ -1,8 +1,77 @@
+syntax: glob
+
+# Temporary, cache, swap files
+\#\#* 
 *.swp
-build*
+*.bkp
+
+# Files which "ask" to be hidden
+*~
+.*
+unused/
+
+# Build artifacts
+*.a
+*.o
+*.so
+*.ptx
+bin/*
+lib/*
+build/
+build-*/
+bazel-*
+
+# Core dumps
+core
+core.*
+core-*
+
+# CMake & CTest-generated files
 CMakeCache.txt
-Makefile
 CMakeFiles/
-Testing/
-CTestTestfile.cmake
 cmake_install.cmake
+CMakeScripts/*
+CMakeTmp/*
+Makefile
+CTestTestfile.cmake
+Testing/
+
+# Eclise IDE-related files
+.project
+.cproject
+.settings
+
+# CLion IDE-related files
+.idea/
+cmake-build-*/
+
+# Patching
+*.diff
+*.rej
+*.orig
+
+# Files/folders downloaded from other repositories as part of the build
+external/*
+third-party/*
+
+# Miscellaneous
+tags
+log
+*.log
+*.v3breakpoints
+gmon.out
+.DS_Store
+
+# Doxygen
+doxygen.log
+Doxyfile
+docs/
+
+# Archives
+*.zip
+*.gz
+*.bz2
+*.tgz
+*.tar
+*.xz
+

.tipi/deps

@@ -0,0 +1 @@
+{ }

.tipi/opts

@@ -0,0 +1 @@
+ 

.travis.yml

@@ -2,18 +2,47 @@ sudo: required
 dist: trusty
 language: cpp
 os:
-  - osx
+  - linux
 matrix:
   include:
+    - os: linux
+      env: COMPILER=g++-6
+      addons:
+        apt:
+          packages:
+            - g++-6
+          sources: &sources
+            - llvm-toolchain-trusty-3.8
+            - llvm-toolchain-trusty-5.0
+            - ubuntu-toolchain-r-test
+    - os: linux
+      env: COMPILER=g++-6 UNICODE_OPTIONS=-DCXXOPTS_USE_UNICODE_HELP=Yes
+      addons:
+        apt:
+          packages:
+            - g++-6
+          sources: *sources
+    - os: linux
+      env: COMPILER=g++-7
+      addons:
+        apt:
+          packages:
+            - g++-7
+          sources: *sources
+    - os: linux
+      env: COMPILER=g++-7 UNICODE_OPTIONS=-DCXXOPTS_USE_UNICODE_HELP=Yes
+      addons:
+        apt:
+          packages:
+            - g++-7
+          sources: *sources
     - os: linux
       env: COMPILER=g++-5
       addons:
         apt:
           packages:
             - g++-5
-          sources: &sources
-            - llvm-toolchain-precise-3.8
-            - ubuntu-toolchain-r-test
+          sources: *sources
     - os: linux
       env: COMPILER=g++-5 UNICODE_OPTIONS=-DCXXOPTS_USE_UNICODE_HELP=Yes
       addons:
@@ -21,6 +50,20 @@ matrix:
           packages:
             - g++-5
           sources: *sources
+    - os: linux
+      env: COMPILER=g++-4.8
+      addons:
+        apt:
+          packages:
+            - g++-4.8
+          sources: *sources
+    - os: linux
+      env: COMPILER=g++-4.8 UNICODE_OPTIONS=-DCXXOPTS_USE_UNICODE_HELP=Yes
+      addons:
+        apt:
+          packages:
+            - g++-4.8
+          sources: *sources
     - os: linux
       env: COMPILER=clang++-3.8 CXXFLAGS=-stdlib=libc++
       addons:
@@ -37,9 +80,17 @@ matrix:
             - clang-3.8
             - libc++-dev
           sources: *sources
+    - os: linux
+      env: COMPILER=clang++-5.0 CMAKE_OPTIONS=-DCXXOPTS_CXX_STANDARD=17
+      addons:
+        apt:
+          packages:
+            - clang-5.0
+            - g++-5
+          sources: *sources
 script: >
-    cmake -DCXXOPTS_BUILD_TESTS=ON -DCMAKE_CXX_COMPILER=$COMPILER
-    -DCMAKE_CXX_FLAGS=$CXXFLAGS $UNICODE_OPTIONS .
+    cmake -Werror=dev -DCXXOPTS_BUILD_TESTS=ON -DCMAKE_CXX_COMPILER=$COMPILER
+    -DCMAKE_CXX_FLAGS=$CXXFLAGS $UNICODE_OPTIONS $CMAKE_OPTIONS .
     && make && make ARGS=--output-on-failure test
 
 before_install:

BUILD.bazel

@@ -0,0 +1,16 @@
+load("@rules_cc//cc:defs.bzl", "cc_library")
+
+cc_library(
+    name = "cxxopts",
+    hdrs = ["include/cxxopts.hpp"],
+    strip_include_prefix = "include",
+    visibility = ["//visibility:public"],
+)
+
+load("@rules_fuzzing//fuzzing:cc_defs.bzl", "cc_fuzz_test")
+
+cc_fuzz_test(
+    name = "cxxopts_fuzz_test",
+    srcs = ["test/fuzz.cpp"],
+    deps = [":cxxopts"],
+)

CHANGELOG.md

@@ -0,0 +1,183 @@
+# Changelog
+
+This is the changelog for `cxxopts`, a C++11 library for parsing command line
+options. The project adheres to semantic versioning.
+
+## 3.3.1
+
+### Bug fixes
+
+* Added missing version bump
+
+## 3.3.0
+
+### Bug fixes
+
+* Added missing header for GCC 15
+* Fix some CMake packaging problems
+
+### Added
+
+* `as_optional`
+* `ParseResult::contains`
+* `std::filesystem` support
+* CMake 4 compatibility
+
+## 3.2.1
+
+### Bug fixes
+
+* Fix compilation with optional on C++20.
+
+## 3.2
+
+### Bug fixes
+
+* Fix unannotated fallthrough.
+* Fix sign conversion with Unicode output.
+* Don't initialize regex in static initialiser.
+* Fix incorrect integer overflow checks.
+
+### Added
+
+* Add fuzzing to CI
+
+### Changed
+
+* Change quote output to '' to match Windows.
+* Don't split positional arguments by the list delimiter.
+* Order help groups by the order they were added.
+
+## 3.1.1
+
+### Bug Fixes
+
+* Fixed version number in header.
+* Fixed cast warning in Unicode function.
+
+## 3.1
+
+### Added
+
+* Support for multiple long names for the same option (= multiple long aliases)
+* Add a `program()` function to retrieve the program name.
+* Added a .clang-format file.
+* Added iterator and printing for a ParseResult.
+
+### Changed
+
+* Cleanup exception code, add cxxopts::exceptions namespace.
+* Renamed several exceptions to be more descriptive, and added to a nested namespace.
+
+### Bug Fixes
+
+* Fix `arguments()` having no key for options that only have a short name.
+
+## 3.0
+
+### Changed
+
+* Only search for a C++ compiler in CMakeLists.txt.
+* Allow for exceptions to be disabled.
+* Fix duplicate default options when there is a short and long option.
+* Add `CXXOPTS_NO_EXCEPTIONS` to disable exceptions.
+* Fix char parsing for space and check for length.
+* Change argument type in `Options::parse` from `char**` to `const char**`.
+* Refactor parser to not change its arguments.
+* `ParseResult` doesn't depend on a reference to the parser.
+* Fixed several warnings and code quality issues.
+* Improved formatting for help descriptions.
+* Improve integer parsing.
+
+### Added
+
+* A list of unmatched arguments is available in `ParseResult`.
+* Support single letter options with argument attached.
+* Use <optional> if it is present.
+
+### Bug Fixes
+
+* Fix missing option name in exception.
+
+## 2.2
+
+### Changed
+
+* Allow integers to have leading zeroes.
+* Build the tests by default.
+* Don't check for container when showing positional help.
+
+### Added
+
+* Iterator inputs to `parse_positional`.
+* Throw an exception if the option in `parse_positional` doesn't exist.
+* Parse a delimited list in a single argument for vector options.
+* Add an option to disable implicit value on booleans.
+
+### Bug Fixes
+
+* Fix a warning about possible loss of data.
+* Fix version numbering in CMakeLists.txt
+* Remove unused declaration of the undefined `ParseResult::get_option`.
+* Throw on invalid option syntax when beginning with a `-`.
+* Throw in `as` when option wasn't present.
+* Fix catching exceptions by reference.
+* Fix out of bounds errors parsing integers.
+
+## 2.1.1
+
+### Bug Fixes
+
+* Revert the change adding `const` type for `argv`, because most users expect
+  to pass a non-const `argv` from `main`.
+
+## 2.1
+
+### Changed
+
+* Options with implicit arguments now require the `--option=value` form if
+  they are to be specified with an option. This is to remove the ambiguity
+  when a positional argument could follow an option with an implicit value.
+  For example, `--foo value`, where `foo` has an implicit value, will be
+  parsed as `--foo=implicit` and a positional argument `value`.
+* Boolean values are no longer special, but are just an option with a default
+  and implicit value.
+
+### Added
+
+* Added support for `std::optional` as a storage type.
+* Allow the help string to be customised.
+* Use `const` for the type in the `argv` parameter, since the contents of the
+  arguments is never modified.
+
+### Bug Fixes
+
+* Building against GCC 4.9 was broken due to overly strict shadow warnings.
+* Fixed an ambiguous overload in the `parse_positional` function when an
+  `initializer_list` was directly passed.
+* Fixed precedence in the Boolean value regex.
+
+## 2.0
+
+### Changed
+
+* `Options::parse` returns a ParseResult rather than storing the parse
+  result internally.
+* Options with default values now get counted as appearing once if they
+  were not specified by the user.
+
+### Added
+
+* A new `ParseResult` object that is the immutable result of parsing. It
+  responds to the same `count` and `operator[]` as `Options` of 1.x did.
+* The function `ParseResult::arguments` returns a vector of the parsed
+  arguments to iterate through in the order they were provided.
+* The symbol `cxxopts::version` for the version of the library.
+* Booleans can be specified with various strings and explicitly set false.
+
+## 1.x
+
+The 1.x series was the first major version of the library, with release numbers
+starting to follow semantic versioning, after 0.x being unstable.  It never had
+a changelog maintained for it. Releases mostly contained bug fixes, with the
+occasional feature added.

CMakeLists.txt

@@ -17,72 +17,67 @@
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
-cmake_minimum_required(VERSION 3.1)
-project(cxxopts)
+cmake_minimum_required(VERSION 3.5...3.19)
 
-enable_testing()
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/")
+include(cxxopts)
 
-set(VERSION "1.2.0")
+# Get the version of the library
+cxxopts_getversion(VERSION)
 
-option(CXXOPTS_BUILD_EXAMPLES "Set to ON to build examples" ON)
-option(CXXOPTS_BUILD_TESTS "Set to ON to build tests" OFF)
+project(cxxopts
+    VERSION "${VERSION}"
+    LANGUAGES CXX
+)
 
-# request c++11 without gnu extension for the whole project and enable more warnings
-set(CMAKE_CXX_STANDARD   11)
-set(CMAKE_CXX_EXTENSIONS OFF)
-if(MSVC)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W2")
-elseif(CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang" OR CMAKE_CXX_COMPILER_ID MATCHES "GNU")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Werror -Wextra -Wshadow")
+set("PROJECT_DESCRIPTION" "A header-only lightweight C++ command line option parser")
+set("PROJECT_HOMEPAGE_URL" "https://github.com/jarro2783/cxxopts")
+
+# Must include after the project call due to GNUInstallDirs requiring a language be enabled (IE. CXX)
+include(GNUInstallDirs)
+
+# Determine whether this is a standalone project or included by other projects
+set(CXXOPTS_STANDALONE_PROJECT OFF)
+if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
+    set(CXXOPTS_STANDALONE_PROJECT ON)
+endif()
+
+# Establish the project options
+option(CXXOPTS_BUILD_EXAMPLES "Set to ON to build examples" ${CXXOPTS_STANDALONE_PROJECT})
+option(CXXOPTS_BUILD_TESTS "Set to ON to build tests" ${CXXOPTS_STANDALONE_PROJECT})
+option(CXXOPTS_ENABLE_INSTALL "Generate the install target" ${CXXOPTS_STANDALONE_PROJECT})
+option(CXXOPTS_ENABLE_WARNINGS "Add warnings to CMAKE_CXX_FLAGS" ${CXXOPTS_STANDALONE_PROJECT})
+option(CXXOPTS_USE_UNICODE_HELP "Use ICU Unicode library" OFF)
+
+if (CXXOPTS_STANDALONE_PROJECT)
+    cxxopts_set_cxx_standard()
+endif()
+
+if (CXXOPTS_ENABLE_WARNINGS)
+    cxxopts_enable_warnings()
 endif()
 
 add_library(cxxopts INTERFACE)
+add_library(cxxopts::cxxopts ALIAS cxxopts)
+add_subdirectory(include)
 
-# optionally, enable unicode support using the ICU library
-set(CXXOPTS_USE_UNICODE_HELP FALSE CACHE BOOL "Use ICU Unicode library")
+# Link against the ICU library when requested
 if(CXXOPTS_USE_UNICODE_HELP)
-    find_package(PkgConfig)
-    pkg_check_modules(ICU REQUIRED icu-uc)
-
-    target_link_libraries(cxxopts INTERFACE ${ICU_LDFLAGS})
-    target_compile_options(cxxopts INTERFACE ${ICU_CFLAGS})
-    target_compile_definitions(cxxopts INTERFACE CXXOPTS_USE_UNICODE)
+    cxxopts_use_unicode()
 endif()
 
-target_include_directories(cxxopts INTERFACE
-    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
-    $<INSTALL_INTERFACE:include>
-    )
+# Install cxxopts when requested by the user
+if (CXXOPTS_ENABLE_INSTALL)
+    cxxopts_install_logic()
+endif()
 
-include(CMakePackageConfigHelpers)
-set(CXXOPTS_CMAKE_DIR "lib/cmake/cxxopts" CACHE STRING
-  "Installation directory for cmake files, relative to ${CMAKE_INSTALL_PREFIX}.")
-set(version_config "${PROJECT_BINARY_DIR}/cxxopts-config-version.cmake")
-set(project_config "${PROJECT_BINARY_DIR}/cxxopts-config.cmake")
-set(targets_export_name cxxopts-targets)
+# Build examples when requested by the user
+if (CXXOPTS_BUILD_EXAMPLES)
+    add_subdirectory(src)
+endif()
 
-# Generate the version, config and target files into the build directory.
-write_basic_package_version_file(
-    ${version_config}
-    VERSION ${VERSION}
-    COMPATIBILITY AnyNewerVersion)
-configure_package_config_file(
-    ${PROJECT_SOURCE_DIR}/cxxopts-config.cmake.in
-    ${project_config}
-    INSTALL_DESTINATION ${CXXOPTS_CMAKE_DIR})
-export(TARGETS cxxopts NAMESPACE cxxopts::
-    FILE ${PROJECT_BINARY_DIR}/${targets_export_name}.cmake)
-
-# Install version, config and target files.
-install(
-    FILES ${project_config} ${version_config}
-    DESTINATION ${CXXOPTS_CMAKE_DIR})
-install(EXPORT ${targets_export_name} DESTINATION ${CXXOPTS_CMAKE_DIR}
-    NAMESPACE cxxopts::)
-
-# Install the header file and export the target
-install(TARGETS cxxopts EXPORT ${targets_export_name} DESTINATION lib)
-install(FILES ${PROJECT_SOURCE_DIR}/include/cxxopts.hpp DESTINATION include)
-
-add_subdirectory(src)
-add_subdirectory(test)
+# Enable testing when requested by the user
+if (CXXOPTS_BUILD_TESTS)
+    enable_testing()
+    add_subdirectory(test)
+endif()

INSTALL

@@ -1,10 +1,46 @@
-It is preferable to build out of source.
+== System installation ==
 
-cmake ${CXXOPTS_DIR}
-make
+This library is header only. So you can either copy `include/cxxopts.hpp` to `/usr/include` or `/usr/local/include`, or add `include` to your search path.
 
+== Building the examples and tests ==
+
+It is preferable to build out of source. Make a build directory somewhere, and then
+do the following, where `${CXXOPTS_DIR}` is the path that you checked out `cxxopts`
+to:
+
+  cmake ${CXXOPTS_DIR}
+  make
 
 You can use another build tool, such as ninja.
 
-cmake -G Ninja ${CXXOPTS_DIR}
-ninja
+  cmake -G Ninja ${CXXOPTS_DIR}
+  ninja
+
+
+To run the tests, you have to configure `cxxopts` with another flag:
+   cmake -D CXXOPTS_BUILD_TESTS=On ${CXXOPTS_DIR}
+   make
+   make test
+
+== Using cxxopts in tipi.build projects ==
+
+`cxxopts` can be easily used in [tipi.build](https://tipi.build) projects simply by adding the following entry to your `.tipi/deps`:
+
+```json
+{
+  "jarro2783/cxxopts": { "@": "v3.0.0" }
+}
+```
+
+To try this you can run the following command in `/src` (change the target name appropriately to `linux` or `macos` or `windows`):
+
+```bash
+tipi . -t <target>
+./build/linux-cxx17/bin/test_package -v
+```
+
+To develop `cxxopts` using tipi run the following command at the root of the repository:
+
+```bash
+tipi . -t <target> --test all -v
+```

README.md

@@ -1,4 +1,41 @@
-[![Build Status](https://travis-ci.org/jarro2783/cxxopts.svg?branch=master)](https://travis-ci.org/jarro2783/cxxopts)
+<div align="center">
+
+[![Build Status](https://img.shields.io/github/actions/workflow/status/jarro2783/cxxopts/cmake.yml?label=build)](https://github.com/jarro2783/cxxopts/actions/workflows/cmake.yml)
+[![Conan](https://img.shields.io/conan/v/cxxopts)](https://conan.io/center/recipes/cxxopts)
+[![vcpkg](https://img.shields.io/vcpkg/v/cxxopts)](https://vcpkg.io/en/package/cxxopts)
+[![GitHub release](https://img.shields.io/github/v/release/jarro2783/cxxopts?label=github%20release)](https://github.com/jarro2783/cxxopts/releases)
+
+[![Header Only](https://img.shields.io/badge/header--only-yes-green.svg)](https://github.com/jarro2783/cxxopts)
+[![Mentioned in Awesome C++](https://awesome.re/mentioned-badge.svg)](https://github.com/fffaraz/awesome-cpp)
+[![Homebrew](https://img.shields.io/homebrew/installs/dy/cxxopts?label=brew%20downloads&logo=homebrew)](https://formulae.brew.sh/formula/cxxopts)
+
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](./LICENSE)
+
+</div>
+
+# Release versions
+
+Note that `master` is generally a work in progress, and you probably want to use a
+tagged release version.
+
+## Version 3 breaking changes
+
+If you have used version 2, there are a couple of breaking changes in version 3
+that you should be aware of. If you are new to `cxxopts` you can skip this
+section.
+
+The parser no longer modifies its arguments, so you can pass a const `argc` and
+`argv` and expect them not to be changed.
+
+The `ParseResult` object no longer depends on the parser. So it can be returned
+from a scope outside the parser and still work. Now that the inputs are not
+modified, `ParseResult` stores a list of the unmatched arguments. These are
+retrieved like follows:
+
+```cpp
+auto result = options.parse(argc, argv);
+result.unmatched(); // get the unmatched arguments
+```
 
 # Quick start
 
@@ -20,18 +57,26 @@ Additionally, anything after `--` will be parsed as a positional argument.
 
 ## Basics
 
-    #include <cxxopts.hpp>
+```cpp
+#include <cxxopts.hpp>
+```
 
-Create a cxxopts::Options instance.
+Create a `cxxopts::Options` instance.
 
-    cxxopts::Options options("MyProgram", "One line description of MyProgram");
+```cpp
+cxxopts::Options options("MyProgram", "One line description of MyProgram");
+```
 
 Then use `add_options`.
 
-    options.add_options()
-      ("d,debug", "Enable debugging")
-      ("f,file", "File name", cxxopts::value<std::string>())
-      ;
+```cpp
+options.add_options()
+  ("d,debug", "Enable debugging") // a bool parameter
+  ("i,integer", "Int param", cxxopts::value<int>())
+  ("f,file", "File name", cxxopts::value<std::string>())
+  ("v,verbose", "Verbose output", cxxopts::value<bool>()->default_value("false"))
+  ;
+```
 
 Options are declared with a long and an optional short option. A description
 must be provided. The third argument is the value, if omitted it is boolean.
@@ -39,32 +84,91 @@ Any type can be given as long as it can be parsed, with operator>>.
 
 To parse the command line do:
 
-    options.parse(argc, argv);
+```cpp
+auto result = options.parse(argc, argv);
+```
 
-To retrieve an option use `options.count("option")` to get the number of times
+To retrieve an option use `result.count("option")` to get the number of times
 it appeared, and
 
-    options["opt"].as<type>()
+```cpp
+result["opt"].as<type>()
+```
 
 to get its value. If "opt" doesn't exist, or isn't of the right type, then an
 exception will be thrown.
 
+## Unrecognised arguments
+
+You can allow unrecognised arguments to be skipped. This applies to both
+positional arguments that are not parsed into another option, and `--`
+arguments that do not match an argument that you specify. This is done by
+calling:
+
+```cpp
+options.allow_unrecognised_options();
+```
+
+and in the result object they are retrieved with:
+
+```cpp
+result.unmatched()
+```
+
+## Exceptions
+
+Exceptional situations throw C++ exceptions. There are two types of
+exceptions: errors defining the options, and errors when parsing a list of
+arguments. All exceptions derive from `cxxopts::exceptions::exception`. Errors
+defining options derive from `cxxopts::exceptions::specification` and errors
+parsing arguments derive from `cxxopts::exceptions::parsing`.
+
+All exceptions define a `what()` function to get a printable string
+explaining the error.
+
 ## Help groups
 
 Options can be placed into groups for the purposes of displaying help messages.
-To place options in a group, pass the group as a string to `add_options`. Then,
-when displaying the help, pass the groups that you would like displayed as a
-vector to the `help` function.
-
+To place options in a group, pass the group as a string to `add_options`. Then, when displaying the help, `help` by default prints help for all groups. If you want to only print help for a specific group, pass the groups that you would like displayed as a vector to the `help` function.
 ## Positional Arguments
 
-Positional arguments can be optionally parsed into one or more options.
-To set up positional arguments, call
+Positional arguments are those given without a preceding flag and can be used
+alongside non-positional arguments. There may be multiple positional arguments,
+and the final positional argument may be a container type to hold a list of all
+remaining positionals.
 
-    options.parse_positional({"first", "second", "last"})
+To set up positional arguments, first declare the options, then configure a
+set of those arguments as positional like:
 
-where "last" should be the name of an option with a container type, and the
-others should have a single value.
+```cpp
+options.add_options()
+  ("script", "The script file to execute", cxxopts::value<std::string>())
+  ("server", "The server to execute on", cxxopts::value<std::string>())
+  ("filenames", "The filename(s) to process", cxxopts::value<std::vector<std::string>>());
+
+options.parse_positional({"script", "server", "filenames"});
+
+// Parse options the usual way
+options.parse(argc, argv);
+```
+
+Note : `parse_positional` defaults to replacing the positionals with the arguments provided in the function call. To append to the existing list of positionals, please use `cxxopts::PositionalMode::Append`.
+
+```cpp
+options.parse_positional("another_option", cxxopts::PositionalMode::Append);
+```
+
+For example, parsing the following arguments:
+~~~
+my_script.py my_server.com file1.txt file2.txt file3.txt
+~~~
+will result in parsed arguments like the following table:
+
+| Field         | Value                                     |
+| ------------- | ----------------------------------------- |
+| `"script"`    | `"my_script.py"`                          |
+| `"server"`    | `"my_server.com"`                         |
+| `"filenames"` | `{"file1.txt", "file2.txt", "file3.txt"}` |
 
 ## Default and implicit values
 
@@ -73,29 +177,141 @@ An option can be declared with a default or an implicit value, or both.
 A default value is the value that an option takes when it is not specified
 on the command line. The following specifies a default value for an option:
 
-    cxxopts::value<std::string>()->default_value("value")
+```cpp
+cxxopts::value<std::string>()->default_value("value")
+```
 
 An implicit value is the value that an option takes when it is given on the
 command line without an argument. The following specifies an implicit value:
 
-    cxxopts::value<std::string>()->implicit_value("implicit")
+```cpp
+cxxopts::value<std::string>()->implicit_value("implicit")
+```
 
 If an option had both, then not specifying it would give the value `"value"`,
 writing it on the command line as `--option` would give the value `"implicit"`,
 and writing `--option=another` would give it the value `"another"`.
 
+Note that if `option` has an implicit value, specifying `--option another` will not work. You must use `=` syntax - `--option=another` or `-o=another`(assumming `o` is a short name for the option). This is because no argument is required. Hence, there is no good way to determine if the next string is an argument to your option or a positional argument.
+
+Note that the default and implicit value is always stored as a string,
+regardless of the type that you want to store it in. It will be parsed as
+though it was given on the command line.
+
+Default values are not counted by `Options::count`.
+
+### Implicit values with disabled arguments
+
+You can specify an option for which an argument cannot be specified using below syntax.
+
+```cpp
+cxxopts::value<bool>()->implicit_value("true", cxxopts::ImplicitArgPolicy::Disabled)
+```
+
+In this case specifying option as `--option=<value>` is disallowed and will throw `specified_disabled_args` exception. Note that `--option value` is not supported for implicit values. It is treated as positional/unmatched.
+
+## Boolean values
+
+Boolean options have a default implicit value of `"true"`, which can be
+overridden. The effect is that writing `-o` by itself will set option `o` to
+`true`. However, they can also be written with various strings using `=value`.
+There is no way to disambiguate positional arguments from the value following
+a boolean, so we have chosen that they will be positional arguments, and
+therefore, `-o false` does not work.
+
+## `std::vector<T>` values
+
+Parsing a list of values into a `std::vector<T>` is also supported, as long as `T`
+can be parsed. To separate single values in a list the define symbol `CXXOPTS_VECTOR_DELIMITER`
+is used, which is ',' by default. Ensure that you use no whitespaces between values
+(unless the entire list is double quoted) because those would be interpreted as the
+next command line option. Example for a command line option
+that can be parsed as a `std::vector<double>`:
+
+~~~
+--my_list=1,-2.1,3,4.5
+~~~
+
+If the list of values is quoted, then spaces can be included. For example:
+
+~~~
+--my_list="review,memory sanitize,build help,reformat"
+~~~
+
+This will be parsed into `review`, `memory sanitize`, `build help`, and `reformat`.
+
+## Options specified multiple times
+
+The same option can be specified several times, with different arguments, which will all
+be recorded in order of appearance. An example:
+
+~~~
+--use train --use bus --use ferry
+~~~
+
+this is supported through the use of a vector of value for the option:
+
+~~~
+options.add_options()
+  ("use", "Usable means of transport", cxxopts::value<std::vector<std::string>>())
+~~~
+
+## Custom help
+
+The string after the program name on the first line of the help can be
+completely replaced by calling `options.custom_help`. Note that you might
+also want to override the positional help by calling `options.positional_help`.
+
+
+## Example
+
+Putting all together:
+```cpp
+#include <iostream>
+#include "cxxopts.hpp"
+
+int main(int argc, char** argv)
+{
+    cxxopts::Options options("test", "A brief description");
+
+    options.add_options()
+        ("b,bar", "Param bar", cxxopts::value<std::string>())
+        ("d,debug", "Enable debugging", cxxopts::value<bool>()->default_value("false"))
+        ("f,foo", "Param foo", cxxopts::value<int>()->default_value("10"))
+        ("h,help", "Print usage")
+    ;
+
+    auto result = options.parse(argc, argv);
+
+    if (result.count("help"))
+    {
+      std::cout << options.help() << std::endl;
+      exit(0);
+    }
+    bool debug = result["debug"].as<bool>();
+    std::string bar;
+    if (result.count("bar"))
+      bar = result["bar"].as<std::string>();
+    int foo = result["foo"].as<int>();
+
+    return 0;
+}
+```
+
 # Linking
 
 This is a header only library.
 
 # Requirements
 
-The only build requirement is a C++ compiler that supports C++11 regular
-expressions. For example GCC >= 4.9 or clang with libc++.
+The only build requirement is a C++ compiler that supports C++11 features such as:
 
+* regex
+* constexpr
+* default constructors
 
-# TODO list
+GCC >= 4.9 or clang >= 3.1 with libc++ are known to work.
 
-* Allow unrecognised options.
-* Various help strings.
-* Unicode aware for help strings.
+The following compilers are known not to work:
+
+* MSVC 2013

WORKSPACE

@@ -0,0 +1,16 @@
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+    name = "rules_fuzzing",
+    sha256 = "d9002dd3cd6437017f08593124fdd1b13b3473c7b929ceb0e60d317cb9346118",
+    strip_prefix = "rules_fuzzing-0.3.2",
+    urls = ["https://github.com/bazelbuild/rules_fuzzing/archive/v0.3.2.zip"],
+)
+
+load("@rules_fuzzing//fuzzing:repositories.bzl", "rules_fuzzing_dependencies")
+
+rules_fuzzing_dependencies()
+
+load("@rules_fuzzing//fuzzing:init.bzl", "rules_fuzzing_init")
+
+rules_fuzzing_init()

cmake/cxxopts.cmake

@@ -0,0 +1,169 @@
+# Copyright (c) 2014 Jarryd Beck
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+if (CMAKE_VERSION VERSION_GREATER 3.10 OR CMAKE_VERSION VERSION_EQUAL 3.10)
+    # Use include_guard() added in cmake 3.10
+    include_guard()
+endif()
+
+include(CMakePackageConfigHelpers)
+
+function(cxxopts_getversion version_arg)
+    # Parse the current version from the cxxopts header
+    file(STRINGS "${CMAKE_CURRENT_SOURCE_DIR}/include/cxxopts.hpp" cxxopts_version_defines
+        REGEX "#define CXXOPTS__VERSION_(MAJOR|MINOR|PATCH)")
+    foreach(ver ${cxxopts_version_defines})
+        if(ver MATCHES "#define CXXOPTS__VERSION_(MAJOR|MINOR|PATCH) +([^ ]+)$")
+            set(CXXOPTS__VERSION_${CMAKE_MATCH_1} "${CMAKE_MATCH_2}" CACHE INTERNAL "")
+        endif()
+    endforeach()
+    set(VERSION ${CXXOPTS__VERSION_MAJOR}.${CXXOPTS__VERSION_MINOR}.${CXXOPTS__VERSION_PATCH})
+
+    # Give feedback to the user. Prefer DEBUG when available since large projects tend to have a lot
+    # going on already
+    if (CMAKE_VERSION VERSION_GREATER 3.15 OR CMAKE_VERSION VERSION_EQUAL 3.15)
+        message(DEBUG "cxxopts version ${VERSION}")
+    else()
+        message(STATUS "cxxopts version ${VERSION}")
+    endif()
+
+    # Return the information to the caller
+    set(${version_arg} ${VERSION} PARENT_SCOPE)
+endfunction()
+
+# Optionally, enable unicode support using the ICU library
+function(cxxopts_use_unicode)
+    find_package(PkgConfig)
+    pkg_check_modules(ICU REQUIRED icu-uc)
+
+    target_link_libraries(cxxopts INTERFACE ${ICU_LDFLAGS})
+    target_compile_options(cxxopts INTERFACE ${ICU_CFLAGS})
+    target_compile_definitions(cxxopts INTERFACE CXXOPTS_USE_UNICODE)
+endfunction()
+
+# Request C++11 without gnu extension for the whole project and enable more warnings
+macro(cxxopts_set_cxx_standard)
+    if (CXXOPTS_CXX_STANDARD)
+        set(CMAKE_CXX_STANDARD ${CXXOPTS_CXX_STANDARD})
+    else()
+        set(CMAKE_CXX_STANDARD 11)
+    endif()
+
+    set(CMAKE_CXX_EXTENSIONS OFF)
+endmacro()
+
+# Helper function to enable warnings
+function(cxxopts_enable_warnings)
+    if(MSVC)
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W2")
+    elseif(CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang" OR CMAKE_CXX_COMPILER_ID MATCHES "GNU")
+      if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
+          if (${CMAKE_CXX_COMPILER_VERSION} VERSION_GREATER_EQUAL 5.0)
+            set(COMPILER_SPECIFIC_FLAGS "-Wsuggest-override")
+          endif()
+      endif()
+
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Werror -Wextra -Wshadow -Weffc++ -Wsign-compare -Wshadow -Wwrite-strings -Wpointer-arith -Winit-self -Wconversion -Wno-sign-conversion ${COMPILER_SPECIFIC_FLAGS}")
+    endif()
+
+    set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} PARENT_SCOPE)
+endfunction()
+
+# Helper function to ecapsulate install logic
+function(cxxopts_install_logic)
+    if(NOT CXXOPTS_USE_UNICODE_HELP)
+        if(CMAKE_LIBRARY_ARCHITECTURE)
+            string(REPLACE "/${CMAKE_LIBRARY_ARCHITECTURE}" "" CMAKE_INSTALL_LIBDIR_ARCHIND "${CMAKE_INSTALL_LIBDIR}")
+        else()
+            # On some systems (e.g. NixOS), `CMAKE_LIBRARY_ARCHITECTURE` can be empty
+            set(CMAKE_INSTALL_LIBDIR_ARCHIND "${CMAKE_INSTALL_DATAROOTDIR}")
+        endif()
+        if(${CMAKE_VERSION} VERSION_GREATER "3.14")
+            set(OPTIONAL_ARCH_INDEPENDENT "ARCH_INDEPENDENT")
+        endif()
+    else()
+        set(CMAKE_INSTALL_LIBDIR_ARCHIND "${CMAKE_INSTALL_LIBDIR}")
+    endif()
+    set(CXXOPTS_CMAKE_DIR "${CMAKE_INSTALL_LIBDIR_ARCHIND}/cmake/cxxopts" CACHE STRING "Installation directory for cmake files, relative to ${CMAKE_INSTALL_PREFIX}.")
+    set(version_config "${PROJECT_BINARY_DIR}/cxxopts-config-version.cmake")
+    set(project_config "${PROJECT_BINARY_DIR}/cxxopts-config.cmake")
+    set(targets_export_name cxxopts-targets)
+    set(PackagingTemplatesDir "${PROJECT_SOURCE_DIR}/packaging")
+
+    # Generate the version, config and target files into the build directory.
+    write_basic_package_version_file(
+        ${version_config}
+        VERSION ${VERSION}
+        COMPATIBILITY AnyNewerVersion
+        ${OPTIONAL_ARCH_INDEPENDENT}
+    )
+    configure_package_config_file(
+        ${PackagingTemplatesDir}/cxxopts-config.cmake.in
+        ${project_config}
+        INSTALL_DESTINATION ${CXXOPTS_CMAKE_DIR})
+    export(TARGETS cxxopts NAMESPACE cxxopts::
+        FILE ${PROJECT_BINARY_DIR}/${targets_export_name}.cmake)
+
+    # Install version, config and target files.
+    install(
+        FILES ${project_config} ${version_config}
+        DESTINATION ${CXXOPTS_CMAKE_DIR})
+    install(EXPORT ${targets_export_name} DESTINATION ${CXXOPTS_CMAKE_DIR}
+        NAMESPACE cxxopts::)
+
+    # Install the header file and export the target
+    install(TARGETS cxxopts EXPORT ${targets_export_name} DESTINATION ${CMAKE_INSTALL_LIBDIR})
+    install(FILES ${PROJECT_SOURCE_DIR}/include/cxxopts.hpp DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+
+
+    set(CPACK_PACKAGE_NAME "${PROJECT_NAME}")
+    set(CPACK_PACKAGE_VENDOR "cxxopt developers")
+    set(CPACK_PACKAGE_DESCRIPTION "${PROJECT_DESCRIPTION}")
+    set(CPACK_DEBIAN_PACKAGE_NAME "${CPACK_PACKAGE_NAME}")
+    set(CPACK_RPM_PACKAGE_NAME "${CPACK_PACKAGE_NAME}")
+    set(CPACK_PACKAGE_HOMEPAGE_URL "${PROJECT_HOMEPAGE_URL}")
+    set(CPACK_PACKAGE_MAINTAINER "${CPACK_PACKAGE_VENDOR}")
+    set(CPACK_DEBIAN_PACKAGE_MAINTAINER "${CPACK_PACKAGE_MAINTAINER}")
+    set(CPACK_RESOURCE_FILE_LICENSE "${CMAKE_CURRENT_SOURCE_DIR}/LICENSE")
+    set(CPACK_RESOURCE_FILE_README "${CMAKE_CURRENT_SOURCE_DIR}/README.md")
+
+    set(CPACK_DEBIAN_PACKAGE_NAME "lib${PROJECT_NAME}-dev")
+    set(CPACK_DEBIAN_PACKAGE_DEPENDS "libc6-dev")
+    set(CPACK_DEBIAN_PACKAGE_SUGGESTS "cmake, pkg-config, pkg-conf")
+
+    set(CPACK_RPM_PACKAGE_NAME "lib${PROJECT_NAME}-devel")
+    set(CPACK_RPM_PACKAGE_SUGGESTS "${CPACK_DEBIAN_PACKAGE_SUGGESTS}")
+
+    set(CPACK_DEB_COMPONENT_INSTALL ON)
+    set(CPACK_RPM_COMPONENT_INSTALL ON)
+    set(CPACK_NSIS_COMPONENT_INSTALL ON)
+    set(CPACK_DEBIAN_COMPRESSION_TYPE "xz")
+
+    set(PKG_CONFIG_FILE_NAME "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}.pc")
+    if(CXXOPTS_USE_UNICODE_HELP)
+        set(PKG_CONFIG_REQUIRES "icu-uc")
+        set(PKG_CONFIG_EXTRA_CFLAGS "-DCXXOPTS_USE_UNICODE")
+    endif()
+    configure_file("${PackagingTemplatesDir}/pkgconfig.pc.in" "${PKG_CONFIG_FILE_NAME}" @ONLY)
+    install(FILES "${PKG_CONFIG_FILE_NAME}"
+            DESTINATION "${CMAKE_INSTALL_LIBDIR_ARCHIND}/pkgconfig"
+    )
+
+    include(CPack)
+endfunction()

include/CMakeLists.txt

@@ -0,0 +1,23 @@
+# Copyright (c) 2014 Jarryd Beck
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+target_include_directories(cxxopts INTERFACE
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
+    $<INSTALL_INTERFACE:include>
+)

meson.build

@@ -0,0 +1,97 @@
+# Copyright © 2024-2026 Dylan Baker
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+project(
+  'cxxopts',
+  'cpp',
+  version : run_command(
+    'meson/version.py', files('include/cxxopts.hpp'), capture : true, check : true).stdout().strip(),
+  meson_version : '>= 0.64',
+  license : 'MIT',
+  default_options : ['cpp_std=c++11', 'warning_level=2'],
+)
+
+cpp = meson.get_compiler('cpp')
+
+with_warnings = get_option('warnings').disable_auto_if(meson.is_subproject()).allowed()
+if with_warnings
+  add_project_arguments(
+    cpp.get_supported_arguments(
+      '-Wsuggest-override',
+      '-Wshadow',
+      '-Weffc++',
+      '-Wsign-compare',
+      '-Wshadow',
+      '-Wwrite-strings',
+      '-Wpointer-arith',
+      '-Winit-self',
+      '-Wconversion',
+      '-Wno-sign-conversion',
+    ),
+    language : 'cpp',
+  )
+endif
+
+install_headers('include/cxxopts.hpp')
+
+dep_icu = dependency('icu-uc', required : get_option('icu'))
+if dep_icu.found()
+  add_project_arguments('-DCXXOPTS_USE_UNICODE', language : 'cpp')
+endif
+
+with_examples = get_option('examples').disable_auto_if(meson.is_subproject()).allowed()
+if with_examples
+  executable(
+    'example',
+    'src/example.cpp',
+    include_directories : 'include',
+    dependencies : dep_icu,
+    override_options : ['cpp_std=c++17'],
+  )
+endif
+
+with_tests = get_option('tests').disable_auto_if(meson.is_subproject()).allowed()
+if with_tests
+  subdir('test')
+endif
+
+extra_cflags = []
+if dep_icu.found()
+  extra_cflags += ['-DCXXOPTS_USE_UNICODE']
+endif
+
+dep_cxxopts = declare_dependency(
+  include_directories : 'include',
+  dependencies : dep_icu,
+  compile_args : extra_cflags,
+)
+
+meson.override_dependency('cxxopts', dep_cxxopts)
+
+pkg = import('pkgconfig')
+
+pkg.generate(
+  name : 'cxxopts',
+  description : 'A header-only lightweight C++ command line option parser',
+  url : 'https://github.com/jarro2783/cxxopts',
+  extra_cflags : extra_cflags,
+  requires : dep_icu,
+  dataonly : not dep_icu.found(),
+)

meson/version.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+# Copyright © 2024-2026 Dylan Baker
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+"""Parse the cxxopts.hpp header to get the version."""
+
+import sys
+
+def main():
+    versions = [None, None, None]
+    with open(sys.argv[1], 'r', encoding='ascii') as f:
+        for line in f:
+            if line.startswith('#define CXXOPTS__VERSION_'):
+                ver = line.rstrip().rsplit(' ', 1)[-1]
+                if 'MAJOR' in line:
+                    versions[0] = ver
+                elif 'MINOR' in line:
+                    versions[1] = ver
+                elif 'PATCH' in line:
+                    versions[2] = ver
+                if None not in versions:
+                    break
+
+    assert None not in versions, \
+        "Did not find all of the expected version strings in cxxopts.hpp"
+    print('.'.join(versions))
+
+
+if __name__ == "__main__":
+    main()

meson_options.txt

@@ -0,0 +1,41 @@
+# Copyright © 2024-2026 Dylan Baker
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+option(
+  'examples',
+  type : 'feature',
+  description : 'Whether to build examples. Defaults to enabled when not built as a subproject, otherwise disabled.',
+)
+option(
+  'tests',
+  type : 'feature',
+  description : 'Whether to build tests. Defaults to enabled when not built as a subproject, otherwise disabled.',
+)
+option(
+  'warnings',
+  type : 'feature',
+  description : 'Whether to add additional warnings. Defaults to enabled when not built as a subproject, otherwise disabled.',
+)
+option(
+  'icu',
+  type : 'feature',
+  value : 'disabled',
+  description : 'use ICU Unicode library.',
+)

packaging/pkgconfig.pc.in

@@ -0,0 +1,9 @@
+prefix=@CMAKE_INSTALL_PREFIX@
+includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+
+Name: @PROJECT_NAME@
+Description: @PROJECT_DESCRIPTION@
+URL: @PROJECT_HOMEPAGE_URL@
+Version: @PROJECT_VERSION@
+Requires: @PKG_CONFIG_REQUIRES@
+Cflags: -I${includedir} @PKG_CONFIG_EXTRA_CFLAGS@

src/.tipi/deps

@@ -0,0 +1,3 @@
+{
+    "jarro2783/cxxopts": { }
+}

src/CMakeLists.txt

@@ -18,7 +18,9 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
-if(CXXOPTS_BUILD_EXAMPLES)
-    add_executable(example example.cpp)
-    target_link_libraries(example cxxopts)
-endif()
+add_executable(example example.cpp)
+target_link_libraries(example cxxopts)
+
+target_compile_features(example PRIVATE cxx_std_17)
+target_compile_options(example PRIVATE
+    "$<$<CXX_COMPILER_ID:MSVC>:/utf-8;>")

src/example.cpp

@@ -21,36 +21,51 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 
 */
-
-#include <iostream>
-
 #include "cxxopts.hpp"
 
-int main(int argc, char* argv[])
+#include <iostream>
+#include <memory>
+
+int
+parse(int argc, const char* argv[])
 {
   try
   {
-    cxxopts::Options options(argv[0], " - example command line options");
-    options.positional_help("[optional args]");
+    std::unique_ptr<cxxopts::Options> allocated(new cxxopts::Options(argv[0], " - example command line options"));
+    auto& options = *allocated;
+    options
+      .positional_help("[optional args]")
+      .show_positional_help();
 
     bool apple = false;
 
-    options.add_options()
-      ("a,apple", "an apple", cxxopts::value<bool>(apple))
+    options
+      .set_width(70)
+      .set_tab_expansion()
+      .allow_unrecognised_options()
+      .add_options()
+      ("a,apple,ringo", "an apple", cxxopts::value<bool>(apple))
       ("b,bob", "Bob")
+      ("char", "A character", cxxopts::value<char>())
+      ("t,true", "True", cxxopts::value<bool>()->default_value("true"))
       ("f, file", "File", cxxopts::value<std::vector<std::string>>(), "FILE")
       ("i,input", "Input", cxxopts::value<std::string>())
       ("o,output", "Output file", cxxopts::value<std::string>()
           ->default_value("a.out")->implicit_value("b.def"), "BIN")
+      ("x", "A short-only option", cxxopts::value<std::string>())
       ("positional",
         "Positional arguments: these are the arguments that are entered "
         "without an option", cxxopts::value<std::vector<std::string>>())
       ("long-description",
         "thisisareallylongwordthattakesupthewholelineandcannotbebrokenataspace")
       ("help", "Print help")
+      ("tab-expansion", "Tab\texpansion")
       ("int", "An integer", cxxopts::value<int>(), "N")
       ("float", "A floating point number", cxxopts::value<float>())
+      ("vector", "A list of doubles", cxxopts::value<std::vector<double>>())
       ("option_that_is_too_long_for_the_help", "A very long option")
+      ("l,list", "List all parsed arguments (including default values)")
+      ("range", "Use range-for to list arguments")
     #ifdef CXXOPTS_USE_UNICODE
       ("unicode", u8"A help option with non-ascii: à. Here the size of the"
         " string should be correct")
@@ -63,28 +78,49 @@ int main(int argc, char* argv[])
 
     options.parse_positional({"input", "output", "positional"});
 
-    options.parse(argc, argv);
+    auto result = options.parse(argc, argv);
 
-    if (options.count("help"))
+    if (result.count("help"))
     {
       std::cout << options.help({"", "Group"}) << std::endl;
-      exit(0);
+      return true;
+    }
+
+    if(result.count("list"))
+    {
+      if(result.count("range"))
+      {
+        for(const auto &kv: result)
+        {
+          std::cout << kv.key() << " = " << kv.value() << std::endl;
+        }
+      }
+      else
+      {
+        std::cout << result.arguments_string() << std::endl;
+      }
+      return true;
     }
 
     if (apple)
     {
-      std::cout << "Saw option ‘a’ " << options.count("a") << " times " <<
+      std::cout << "Saw option ‘a’ " << result.count("a") << " times " <<
         std::endl;
     }
 
-    if (options.count("b"))
+    if (result.count("b"))
     {
       std::cout << "Saw option ‘b’" << std::endl;
     }
 
-    if (options.count("f"))
+    if (result.count("char"))
     {
-      auto& ff = options["f"].as<std::vector<std::string>>();
+      std::cout << "Saw a character ‘" << result["char"].as<char>() << "’" << std::endl;
+    }
+
+    if (result.count("f"))
+    {
+      auto& ff = result["f"].as<std::vector<std::string>>();
       std::cout << "Files" << std::endl;
       for (const auto& f : ff)
       {
@@ -92,44 +128,74 @@ int main(int argc, char* argv[])
       }
     }
 
-    if (options.count("input"))
+    if (result.count("input"))
     {
-      std::cout << "Input = " << options["input"].as<std::string>()
+      std::cout << "Input = " << result["input"].as<std::string>()
         << std::endl;
     }
 
-    if (options.count("output"))
+    if (result.count("output"))
     {
-      std::cout << "Output = " << options["output"].as<std::string>()
+      std::cout << "Output = " << result["output"].as<std::string>()
         << std::endl;
     }
 
-    if (options.count("positional"))
+    if (result.count("positional"))
     {
       std::cout << "Positional = {";
-      auto& v = options["positional"].as<std::vector<std::string>>();
+      auto& v = result["positional"].as<std::vector<std::string>>();
       for (const auto& s : v) {
         std::cout << s << ", ";
       }
       std::cout << "}" << std::endl;
     }
 
-    if (options.count("int"))
+    if (result.count("int"))
     {
-      std::cout << "int = " << options["int"].as<int>() << std::endl;
+      std::cout << "int = " << result["int"].as<int>() << std::endl;
     }
 
-    if (options.count("float"))
+    if (result.count("float"))
     {
-      std::cout << "float = " << options["float"].as<float>() << std::endl;
+      std::cout << "float = " << result["float"].as<float>() << std::endl;
+    }
+
+    if (result.count("vector"))
+    {
+      std::cout << "vector = ";
+      const auto values = result["vector"].as<std::vector<double>>();
+      for (const auto& v : values) {
+        std::cout << v << ", ";
+      }
+      std::cout << std::endl;
     }
 
     std::cout << "Arguments remain = " << argc << std::endl;
 
-  } catch (const cxxopts::OptionException& e)
+    auto arguments = result.arguments();
+    std::cout << "Saw " << arguments.size() << " arguments" << std::endl;
+
+    std::cout << "Unmatched options: ";
+    for (const auto& option: result.unmatched())
+    {
+      std::cout << "'" << option << "' ";
+    }
+    std::cout << std::endl;
+  }
+  catch (const cxxopts::exceptions::exception& e)
   {
     std::cout << "error parsing options: " << e.what() << std::endl;
-    exit(1);
+    return false;
+  }
+
+  return true;
+}
+
+int main(int argc, const char* argv[])
+{
+  if (!parse(argc, argv))
+  {
+    return 1;
   }
 
   return 0;

test/.tipiignore

@@ -0,0 +1,2 @@
+link_a.cpp
+link_b.cpp

test/CMakeLists.txt

@@ -1,32 +1,78 @@
-if (CXXOPTS_BUILD_TESTS)
-    add_executable(options_test main.cpp options.cpp)
-    target_link_libraries(options_test cxxopts)
-    add_test(options options_test)
+# Copyright (c) 2014 Jarryd Beck
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
 
-    # test if the targets are findable from the build directory
-    add_test(find-package-test ${CMAKE_CTEST_COMMAND}
-        -C ${CMAKE_BUILD_TYPE}
-        --build-and-test
-        "${CMAKE_CURRENT_SOURCE_DIR}/find-package-test"
-        "${CMAKE_CURRENT_BINARY_DIR}/find-package-test"
-        --build-generator ${CMAKE_GENERATOR}
-        --build-makeprogram ${CMAKE_MAKE_PROGRAM}
-        --build-options
-        "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
-        "-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}"
-        "-Dcxxopts_DIR=${PROJECT_BINARY_DIR}"
-    )
+add_executable(options_test main.cpp options.cpp)
+target_link_libraries(options_test cxxopts)
+add_test(options options_test)
 
-    # test if the targets are findable when add_subdirectory is used
-    add_test(add-subdirectory-test ${CMAKE_CTEST_COMMAND}
-        -C ${CMAKE_BUILD_TYPE}
-        --build-and-test
-        "${CMAKE_CURRENT_SOURCE_DIR}/add-subdirectory-test"
-        "${CMAKE_CURRENT_BINARY_DIR}/add-subdirectory-test"
-        --build-generator ${CMAKE_GENERATOR}
-        --build-makeprogram ${CMAKE_MAKE_PROGRAM}
-        --build-options
-        "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
-        "-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}"
-    )
+add_executable(options_test_noregex main.cpp options.cpp)
+target_link_libraries(options_test_noregex cxxopts)
+target_compile_definitions(options_test_noregex PRIVATE CXXOPTS_NO_REGEX)
+add_test(options_no_regex options_test_noregex)
+
+# Run the parser tests under UBSan so undefined behaviour in integer parsing
+# (e.g. std::abs(INT64_MIN)) fails the build instead of going unnoticed.
+if(CMAKE_CXX_COMPILER_ID MATCHES "Clang|GNU" AND NOT WIN32)
+    foreach(test_target options_test options_test_noregex)
+        target_compile_options(${test_target} PRIVATE -fsanitize=undefined -fno-sanitize-recover=undefined)
+        set_target_properties(${test_target} PROPERTIES LINK_FLAGS "-fsanitize=undefined -fno-sanitize-recover=undefined")
+    endforeach()
+endif()
+
+# test if the targets are findable from the build directory
+add_test(find-package-test ${CMAKE_CTEST_COMMAND}
+    -C ${CMAKE_BUILD_TYPE}
+    --build-and-test
+    "${CMAKE_CURRENT_SOURCE_DIR}/find-package-test"
+    "${CMAKE_CURRENT_BINARY_DIR}/find-package-test"
+    --build-generator ${CMAKE_GENERATOR}
+    --build-makeprogram ${CMAKE_MAKE_PROGRAM}
+    --build-options
+    "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
+    "-DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}"
+    "-DCMAKE_CXX_EXTENSIONS=${CMAKE_CXX_EXTENSIONS}"
+    "-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}"
+    "-Dcxxopts_DIR=${PROJECT_BINARY_DIR}"
+)
+
+# test if the targets are findable when add_subdirectory is used
+add_test(add-subdirectory-test ${CMAKE_CTEST_COMMAND}
+    -C ${CMAKE_BUILD_TYPE}
+    --build-and-test
+    "${CMAKE_CURRENT_SOURCE_DIR}/add-subdirectory-test"
+    "${CMAKE_CURRENT_BINARY_DIR}/add-subdirectory-test"
+    --build-generator ${CMAKE_GENERATOR}
+    --build-makeprogram ${CMAKE_MAKE_PROGRAM}
+    --build-options
+    "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
+    "-DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}"
+    "-DCMAKE_CXX_EXTENSIONS=${CMAKE_CXX_EXTENSIONS}"
+    "-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}"
+)
+
+add_executable(link_test link_a.cpp link_b.cpp)
+target_link_libraries(link_test cxxopts)
+
+if(("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang") AND ("${CMAKE_SYSTEM}" MATCHES "Linux"))
+    add_executable(fuzzer fuzz.cpp)
+    target_link_libraries(fuzzer PRIVATE cxxopts)
+    target_compile_options(fuzzer PRIVATE -fsanitize=fuzzer)
+    target_link_options(fuzzer PRIVATE -fsanitize=fuzzer)
 endif()

test/add-subdirectory-test/CMakeLists.txt

@@ -1,10 +1,7 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.5...3.19)
 
 project(cxxopts-test)
 
-set(CMAKE_CXX_STANDARD   11)
-set(CMAKE_CXX_EXTENSIONS OFF)
-
 add_subdirectory(../.. cxxopts EXCLUDE_FROM_ALL)
 
 add_executable(library-test "../../src/example.cpp")

test/find-package-test/CMakeLists.txt

@@ -1,10 +1,7 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.5...3.19)
 
 project(cxxopts-test)
 
-set(CMAKE_CXX_STANDARD   11)
-set(CMAKE_CXX_EXTENSIONS OFF)
-
 find_package(cxxopts REQUIRED)
 
 add_executable(library-test "../../src/example.cpp")

test/fuzz.cpp

@@ -0,0 +1,107 @@
+#include <cassert>
+#include <cxxopts.hpp>
+#include <fuzzer/FuzzedDataProvider.h>
+
+constexpr int kMaxOptions = 1024;
+constexpr int kMaxArgSize = 1024;
+
+enum class ParseableTypes
+{
+  kInt,
+  kString,
+  kVectorString,
+  kFloat,
+  kDouble,
+
+  // Marker for fuzzer.
+  kMaxValue,
+};
+
+template <typename T>
+void
+add_fuzzed_option(cxxopts::Options* options, FuzzedDataProvider* provider)
+{
+  assert(options);
+  assert(provider);
+
+  options->add_options()(provider->ConsumeRandomLengthString(kMaxArgSize),
+                         provider->ConsumeRandomLengthString(kMaxArgSize),
+                         cxxopts::value<T>());
+}
+
+extern "C" int
+LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
+{
+  try
+  {
+    FuzzedDataProvider provider(data, size);
+
+    // Randomly generate a usage string.
+    cxxopts::Options options(provider.ConsumeRandomLengthString(kMaxArgSize),
+                             provider.ConsumeRandomLengthString(kMaxArgSize));
+
+    // Randomly generate a set of flags configurations.
+    for (int i = 0; i < provider.ConsumeIntegralInRange<int>(0, kMaxOptions);
+         i++)
+    {
+      switch (provider.ConsumeEnum<ParseableTypes>())
+      {
+      case ParseableTypes::kInt:
+        add_fuzzed_option<int>(&options, &provider);
+        break;
+      case ParseableTypes::kString:
+        add_fuzzed_option<std::string>(&options, &provider);
+        break;
+      case ParseableTypes::kVectorString:
+        add_fuzzed_option<std::vector<std::string>>(&options, &provider);
+        break;
+      case ParseableTypes::kFloat:
+        add_fuzzed_option<float>(&options, &provider);
+        break;
+      case ParseableTypes::kDouble:
+        add_fuzzed_option<double>(&options, &provider);
+        break;
+      default:
+        break;
+      }
+    }
+    // Sometimes allow unrecognised options.
+    if (provider.ConsumeBool())
+    {
+      options.allow_unrecognised_options();
+    }
+    // Sometimes allow trailing positional arguments.
+    if (provider.ConsumeBool())
+    {
+      std::string positional_option_name =
+        provider.ConsumeRandomLengthString(kMaxArgSize);
+      options.add_options()(positional_option_name,
+                            provider.ConsumeRandomLengthString(kMaxArgSize),
+                            cxxopts::value<std::vector<std::string>>());
+      options.parse_positional({positional_option_name});
+    }
+
+    // Build command line input.
+    const int argc = provider.ConsumeIntegralInRange<int>(1, kMaxOptions);
+
+    std::vector<std::string> command_line_container;
+    command_line_container.reserve(argc);
+
+    std::vector<const char*> argv;
+    argv.reserve(argc);
+
+    for (int i = 0; i < argc; i++)
+    {
+      command_line_container.push_back(
+        provider.ConsumeRandomLengthString(kMaxArgSize));
+      argv.push_back(command_line_container[i].c_str());
+    }
+
+    // Parse command line;
+    auto result = options.parse(argc, argv.data());
+  } catch (...)
+  {
+  }
+
+  return 0;
+}

test/link_a.cpp

@@ -0,0 +1,6 @@
+#include "cxxopts.hpp"
+
+int main(int, char**)
+{
+  return 0;
+}

test/link_b.cpp

@@ -0,0 +1 @@
+#include <cxxopts.hpp>

test/meson.build

@@ -0,0 +1,55 @@
+# Copyright © 2024-2026 Dylan Baker
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+inc = include_directories('../include')
+
+test(
+  'link',
+  executable(
+    'link_test',
+    'link_a.cpp', 'link_b.cpp',
+    dependencies : dep_icu,
+    include_directories : inc,
+  )
+)
+
+test(
+  'options',
+  executable(
+    'options_test',
+    'main.cpp', 'options.cpp',
+    dependencies : dep_icu,
+    include_directories : inc,
+  )
+)
+
+if cpp.get_id() == 'clang' and host_machine.system() == 'linux'
+  executable(
+    'fuzzer',
+    'fuzz.cpp',
+    cpp_args : ['-fsanitize=fuzzer'],
+    link_args : ['-fsanitize=fuzzer'],
+    dependencies : dep_icu,
+    include_directories : inc,
+  )
+endif
+
+# Meson can generate basic cmake-configs files, but not when targets are used,
+# so these tests don't make sense