fix: issue found by fuzzing (#846)

* Add the beginnings of a fuzzing system for CLI11.  This commit adds the fuzzing code, a simple test, and two fixes to issues(seg faults) found by the initial round of fuzzing.  It also adds a few tests and coverage issues uncovered in the process of developing the fuzz tests. As a side effect adjusts some of the azure tests to specify the vmImage which was being changed on azure.

* update license to match rest of code base

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.codecov.yml

@@ -4,3 +4,4 @@ ignore:
   - "book"
   - "docs"
   - "test_package"
+  - "fuzz"

.github/codecov.yml

@@ -1,6 +1,6 @@
 codecov:
   notify:
-    after_n_builds: 4
+    after_n_builds: 8
 coverage:
   status:
     project:

.github/workflows/fuzz.yml

@@ -0,0 +1,54 @@
+name: Fuzz
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+      - v*
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  quick_fuzz1:
+    name: quickfuzz1
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Configure
+        run: |
+          cmake -S . -B build \
+            -DCMAKE_CXX_STANDARD=17 \
+            -DCLI11_SINGLE_FILE_TESTS=OFF \
+            -DCLI11_BUILD_EXAMPLES=OFF \
+            -DCLI11_FUZZ_TARGET=ON \
+            -DCLI11_BUILD_TESTS=OFF \
+            -DCLI11_BUILD_DOCS=OFF \
+            -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_CXX_COMPILER_FORCED=ON \
+            -DCMAKE_CXX_FLAGS="-g -O1 -fsanitize=fuzzer,undefined,address"
+
+      - name: Build
+        run: cmake --build build -j4
+
+      - name: Test
+        run: |
+          cd build
+          make QUICK_CLI11_APP_FUZZ
+
+      - name: Test2
+        run: |
+          cd build
+          make QUICK_CLI11_FILE_FUZZ
+
+
+      - name: artifacts
+        if: failure()
+        uses: actions/upload-artifact@v3
+        with:
+          name: file_failure
+          path: ./build/fuzz/cli11_*_fail_artifact.txt

.github/workflows/tests.yml

@@ -48,7 +48,7 @@ jobs:
       - name: Prepare coverage
         run: |
           lcov --directory . --capture --output-file coverage.info
-          lcov --remove coverage.info '*/tests/*' '*/examples/*' '/usr/*' '*/book/*' --output-file coverage.info
+          lcov --remove coverage.info '*/tests/*' '*/examples/*' '/usr/*' '*/book/*' '*/fuzz/*' --output-file coverage.info
           lcov --list coverage.info
         working-directory: build
 

.pre-commit-config.yaml

@@ -1,3 +1,4 @@
+exclude: ^(.github/workflows/|docs/img/)
 ci:
   autoupdate_commit_msg: "chore(deps): pre-commit.ci autoupdate"
   autofix_commit_msg: "style: pre-commit.ci fixes"

CMakeLists.txt

@@ -132,6 +132,9 @@ endif()
 
 include(CLI11Warnings)
 
+# build the fuzzing example or fuzz entry point
+add_subdirectory(fuzz)
+
 add_subdirectory(src)
 
 # Allow tests to be run on CUDA

azure-pipelines.yml

@@ -28,7 +28,6 @@ jobs:
       - bash: cpplint --counting=detailed --recursive examples include/CLI tests
         displayName: Checking against google style guide
 
-  # TODO: Fix macOS error and windows warning in c++17 mode
   - job: Native
     strategy:
       matrix:
@@ -38,13 +37,13 @@ jobs:
           vmImage: "ubuntu-latest"
           cli11.precompile: ON
         macOS17:
-          vmImage: "macOS-latest"
+          vmImage: "macOS-12"
           cli11.std: 17
         macOS11:
-          vmImage: "macOS-latest"
+          vmImage: "macOS-11"
           cli11.std: 11
         macOS11PC:
-          vmImage: "macOS-latest"
+          vmImage: "macOS-11"
           cli11.std: 11
           cli11.precompile: ON
         Windows17:

fuzz/CMakeLists.txt

@@ -0,0 +1,48 @@
+# Copyright (c) 2017-2023, University of Cincinnati, developed by Henry Schreiner
+# under NSF AWARD 1414736 and by the respective contributors.
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+if(CMAKE_CXX_STANDARD GREATER 16)
+  if(CLI11_FUZZ_TARGET)
+
+    add_executable(cli11_app_fuzzer cli11_app_fuzz.cpp fuzzApp.cpp fuzzApp.hpp)
+    target_link_libraries(cli11_app_fuzzer PUBLIC CLI11)
+    set_property(TARGET cli11_app_fuzzer PROPERTY FOLDER "Tests")
+
+    add_executable(cli11_file_fuzzer cli11_file_fuzz.cpp fuzzApp.cpp fuzzApp.hpp)
+    target_link_libraries(cli11_file_fuzzer PUBLIC CLI11)
+    set_property(TARGET cli11_file_fuzzer PROPERTY FOLDER "Tests")
+
+    if(NOT CLI11_FUZZ_ARTIFACT_PATH)
+      set(CLI11_FUZZ_ARTIFACT_PATH ${PROJECT_BINARY_DIR}/fuzz)
+    endif()
+
+    if(NOT CLI11_FUZZ_TIME)
+      set(CLI11_FUZZ_TIME 360)
+    endif()
+    add_custom_target(
+      QUICK_CLI11_APP_FUZZ
+      COMMAND ${CMAKE_COMMAND} -E make_directory corp
+      COMMAND
+        cli11_app_fuzzer corp -max_total_time=${CLI11_FUZZ_TIME} -max_len=2048
+        -dict=${CMAKE_CURRENT_SOURCE_DIR}/fuzz_dictionary1.txt
+        -exact_artifact_path=${CLI11_FUZZ_ARTIFACT_PATH}/cli11_app_fail_artifact.txt)
+
+    add_custom_target(
+      QUICK_CLI11_FILE_FUZZ
+      COMMAND ${CMAKE_COMMAND} -E make_directory corp
+      COMMAND
+        cli11_file_fuzzer corp -max_total_time=${CLI11_FUZZ_TIME} -max_len=2048
+        -dict=${CMAKE_CURRENT_SOURCE_DIR}/fuzz_dictionary2.txt
+        -exact_artifact_path=${CLI11_FUZZ_ARTIFACT_PATH}/cli11_file_fail_artifact.txt)
+
+  else()
+    if(CLI11_BUILD_EXAMPLES)
+      add_executable(cli11Fuzz fuzzCommand.cpp fuzzApp.cpp fuzzApp.hpp)
+      target_link_libraries(cli11Fuzz PUBLIC CLI11)
+      set_property(TARGET cli11Fuzz PROPERTY FOLDER "Examples")
+    endif()
+  endif()
+endif()

fuzz/cli11_app_fuzz.cpp

@@ -0,0 +1,30 @@
+// Copyright (c) 2017-2023, University of Cincinnati, developed by Henry Schreiner
+// under NSF AWARD 1414736 and by the respective contributors.
+// All rights reserved.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "fuzzApp.hpp"
+#include <CLI/CLI.hpp>
+#include <cstring>
+#include <exception>
+#include <string>
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+    if(Size == 0) {
+        return 0;
+    }
+    std::string parseString(reinterpret_cast<const char *>(Data), Size);
+
+    CLI::FuzzApp fuzzdata;
+
+    auto app = fuzzdata.generateApp();
+    try {
+        app->parse(parseString);
+    } catch(const CLI::ParseError &e) {
+        //(app)->exit(e);
+        // this just indicates we caught an error known by CLI
+    }
+
+    return 0;  // Non-zero return values are reserved for future use.
+}

fuzz/cli11_file_fuzz.cpp

@@ -0,0 +1,31 @@
+// Copyright (c) 2017-2023, University of Cincinnati, developed by Henry Schreiner
+// under NSF AWARD 1414736 and by the respective contributors.
+// All rights reserved.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "fuzzApp.hpp"
+#include <CLI/CLI.hpp>
+#include <cstring>
+#include <exception>
+#include <sstream>
+#include <string>
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+    if(Size == 0) {
+        return 0;
+    }
+    std::string parseString(reinterpret_cast<const char *>(Data), Size);
+    std::stringstream out(parseString);
+    CLI::FuzzApp fuzzdata;
+
+    auto app = fuzzdata.generateApp();
+    try {
+        app->parse_from_stream(out);
+    } catch(const CLI::ParseError &e) {
+        (app)->exit(e);
+        // this just indicates we caught an error known by CLI
+    }
+
+    return 0;  // Non-zero return values are reserved for future use.
+}

fuzz/fuzzApp.cpp

@@ -0,0 +1,85 @@
+// Copyright (c) 2017-2023, University of Cincinnati, developed by Henry Schreiner
+// under NSF AWARD 1414736 and by the respective contributors.
+// All rights reserved.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "fuzzApp.hpp"
+
+namespace CLI {
+/*
+int32_t val32{0};
+    int16_t val16{0};
+    int8_t val8{0};
+    int64_t val64{0};
+
+    uint32_t uval32{0};
+    uint16_t uval16{0};
+    uint8_t uval8{0};
+    uint64_t uval64{0};
+
+    std::atomic<int64_t> atomicval64{0};
+    std::atomic<uint64_t> atomicuval64{0};
+
+    double v1{0};
+    float v2{0};
+
+    std::vector<double> vv1;
+    std::vector<std::string> vstr;
+    std::vector<std::vector<double>> vecvecd;
+    std::vector<std::vector<std::string>> vvs;
+    std::optional<double> od1;
+    std::optional<std::string> ods;
+    std::pair<double, std::string> p1;
+    std::pair<std::vector<double>, std::string> p2;
+    std::tuple<int64_t, uint16_t, std::optional<double>> t1;
+    std::tuple<std::tuple<std::tuple<std::string, double, std::vector<int>>,std::string, double>,std::vector<int>,
+std::optional<std::string>> tcomplex; std::string_view vstrv;
+
+    bool flag1{false};
+    int flagCnt{0};
+    std::atomic<bool> flagAtomic{false};
+    */
+std::shared_ptr<CLI::App> FuzzApp::generateApp() {
+    auto fApp = std::make_shared<CLI::App>("fuzzing App", "fuzzer");
+    fApp->set_config("--config");
+    fApp->add_flag("-a,--flag");
+    fApp->add_flag("-b,--flag2", flag1);
+    fApp->add_flag("-c{34},--flag3{1}", flagCnt)->disable_flag_override();
+    fApp->add_flag("-e,--flagA", flagAtomic);
+
+    fApp->add_option("-d,--opt1", val8);
+    fApp->add_option("--opt2", val16);
+    fApp->add_option("--opt3", val32);
+    fApp->add_option("--opt4", val64);
+
+    fApp->add_option("--opt5", uval8);
+    fApp->add_option("--opt6", uval16);
+    fApp->add_option("--opt7", uval32);
+    fApp->add_option("--opt8", uval64);
+
+    fApp->add_option("--aopt1", atomicval64);
+    fApp->add_option("--aopt2", atomicuval64);
+
+    fApp->add_option("--dopt1", v1);
+    fApp->add_option("--dopt2", v2);
+
+    fApp->add_option("--vopt1", vv1);
+    fApp->add_option("--vopt2", vvs);
+    fApp->add_option("--vopt3", vstr);
+    fApp->add_option("--vopt4", vecvecd);
+
+    fApp->add_option("--oopt1", od1);
+    fApp->add_option("--oopt2", ods);
+
+    fApp->add_option("--tup1", p1);
+    fApp->add_option("--tup2", t1);
+    fApp->add_option("--tup4", tcomplex);
+
+    fApp->add_option("--dwrap", dwrap);
+    fApp->add_option("--iwrap", iwrap);
+
+    return fApp;
+}
+
+}  // namespace CLI

fuzz/fuzzApp.hpp

@@ -0,0 +1,92 @@
+// Copyright (c) 2017-2023, University of Cincinnati, developed by Henry Schreiner
+// under NSF AWARD 1414736 and by the respective contributors.
+// All rights reserved.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+#pragma once
+
+#ifdef CLI11_SINGLE_FILE
+#include "CLI11.hpp"
+#else
+#include "CLI/CLI.hpp"
+#endif
+
+#include <atomic>
+#include <iostream>
+#include <memory>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <vector>
+
+namespace CLI {
+
+class intWrapper64 {
+  public:
+    intWrapper64() = default;
+    explicit intWrapper64(int64_t v) : val(v){};
+    CLI11_NODISCARD int64_t value() const { return val; }
+
+  private:
+    int64_t val{0};
+};
+
+class doubleWrapper {
+  public:
+    doubleWrapper() = default;
+    explicit doubleWrapper(double v) : val(v){};
+    CLI11_NODISCARD double value() const { return val; }
+
+  private:
+    double val{0.0};
+};
+
+class FuzzApp {
+  public:
+    FuzzApp() = default;
+
+    std::shared_ptr<CLI::App> generateApp();
+
+    int32_t val32{0};
+    int16_t val16{0};
+    int8_t val8{0};
+    int64_t val64{0};
+
+    uint32_t uval32{0};
+    uint16_t uval16{0};
+    uint8_t uval8{0};
+    uint64_t uval64{0};
+
+    std::atomic<int64_t> atomicval64{0};
+    std::atomic<uint64_t> atomicuval64{0};
+
+    double v1{0};
+    float v2{0};
+
+    std::vector<double> vv1{};
+    std::vector<std::string> vstr{};
+    std::vector<std::vector<double>> vecvecd{};
+    std::vector<std::vector<std::string>> vvs{};
+    std::optional<double> od1{};
+    std::optional<std::string> ods{};
+    std::pair<double, std::string> p1{};
+    std::pair<std::vector<double>, std::string> p2{};
+    std::tuple<int64_t, uint16_t, std::optional<double>> t1{};
+    std::tuple<std::tuple<std::tuple<std::string, double, std::vector<int>>, std::string, double>,
+               std::vector<int>,
+               std::optional<std::string>>
+        tcomplex{};
+    std::tuple<std::tuple<std::tuple<std::string, double, std::vector<int>>, std::string, double>,
+               std::vector<int>,
+               std::optional<std::string>>
+        tcomplex2{};
+    std::string_view vstrv = "";
+
+    bool flag1{false};
+    int flagCnt{0};
+    std::atomic<bool> flagAtomic{false};
+
+    intWrapper64 iwrap{0};
+    doubleWrapper dwrap{0.0};
+};
+}  // namespace CLI

fuzz/fuzzCommand.cpp

@@ -0,0 +1,24 @@
+// Copyright (c) 2017-2023, University of Cincinnati, developed by Henry Schreiner
+// under NSF AWARD 1414736 and by the respective contributors.
+// All rights reserved.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "fuzzApp.hpp"
+#include <CLI/CLI.hpp>
+#include <iostream>
+
+int main(int argc, char **argv) {
+
+    CLI::FuzzApp fuzzdata;
+
+    auto app = fuzzdata.generateApp();
+    try {
+
+        app->parse(argc, argv);
+    } catch(const CLI::ParseError &e) {
+        (app)->exit(e);
+        // this just indicates we caught an error known by CLI
+    }
+    return 0;
+}

fuzz/fuzz_dictionary1.txt

@@ -0,0 +1,34 @@
+###### Recommended dictionary.
+"-a"
+"-b"
+"-c"
+"-d"
+"-e"
+"--flag1"
+"--flag"
+"--flag2"
+"--flagA"
+"--opt1"
+"--opt2"
+"--opt3"
+"--opt4"
+"--opt5"
+"--opt6"
+"--opt7"
+"--opt8"
+"--opt9"
+"--aopt1"
+"--aopt2"
+"--dopt1"
+"--dopt2"
+"--vopt1"
+"--vopt2"
+"--vopt3"
+"--vopt4"
+"--oopt1"
+"--oopt2"
+"--tup1"
+"--tup2"
+"--tup4"
+"--dwrap"
+"--iwrap"

fuzz/fuzz_dictionary2.txt

@@ -0,0 +1,37 @@
+###### Recommended dictionary.
+"a"
+"b"
+"c"
+"d"
+"e"
+"flag1"
+"flag"
+"flag2"
+"flagA"
+"opt1"
+"opt2"
+"opt3"
+"opt4"
+"opt5"
+"opt6"
+"opt7"
+"opt8"
+"opt9"
+"aopt1"
+"aopt2"
+"dopt1"
+"dopt2"
+"vopt1"
+"vopt2"
+"vopt3"
+"vopt4"
+"="
+"oopt1"
+"oopt2"
+"tup1"
+"tup2"
+"tup4"
+"tup2"
+"tup4"
+"dwrap"
+"iwrap"

include/CLI/TypeTools.hpp

@@ -1239,9 +1239,17 @@ 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;
@@ -1296,11 +1304,13 @@ 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);
+    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);
     if(strings.size() > 1) {
-        retval = retval && lexical_assign<decltype(v2), decltype(v2)>(strings[1], v2);
+        retval = retval && lexical_assign<SecondType, SecondType>(strings[1], v2);
     }
     if(retval) {
         output = AssignTo{v1, v2};
@@ -1460,7 +1470,7 @@ 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])) {
@@ -1470,7 +1480,11 @@ 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;
 }
 

src/CMakeLists.txt

@@ -66,20 +66,22 @@ target_include_directories(
   CLI11 ${SYSTEM_INCL} ${PUBLIC_OR_INTERFACE} $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
   $<INSTALL_INTERFACE:include>)
 
-if(CMAKE_VERSION VERSION_LESS 3.8)
-  # This might not be a complete list
-  target_compile_features(
-    CLI11
-    INTERFACE cxx_lambdas
-              cxx_nullptr
-              cxx_override
-              cxx_range_for
-              cxx_right_angle_brackets
-              cxx_strong_enums
-              cxx_constexpr
-              cxx_auto_type)
-else()
-  target_compile_features(CLI11 INTERFACE cxx_std_11)
+if(CMAKE_CXX_STANDARD LESS 14)
+  if(CMAKE_VERSION VERSION_LESS 3.8)
+    # This might not be a complete list
+    target_compile_features(
+      CLI11
+      INTERFACE cxx_lambdas
+                cxx_nullptr
+                cxx_override
+                cxx_range_for
+                cxx_right_angle_brackets
+                cxx_strong_enums
+                cxx_constexpr
+                cxx_auto_type)
+  else()
+    target_compile_features(CLI11 INTERFACE cxx_std_11)
+  endif()
 endif()
 
 if(CLI11_SINGLE_FILE)

tests/CMakeLists.txt

@@ -56,6 +56,10 @@ if(WIN32)
   list(APPEND CLI11_TESTS WindowsTest)
 endif()
 
+if(CMAKE_CXX_STANDARD GREATER 16)
+  list(APPEND CLI11_TESTS FuzzFailTest)
+endif()
+
 if(Boost_FOUND)
   list(APPEND CLI11_TESTS BoostOptionTypeTest)
 endif()
@@ -169,6 +173,16 @@ foreach(T IN LISTS CLI11_MULTIONLY_TESTS)
   add_catch_test(${T})
 endforeach()
 
+if(CMAKE_CXX_STANDARD GREATER 16)
+  set(TEST_FILE_FOLDER ${CMAKE_CURRENT_SOURCE_DIR})
+  target_compile_definitions(FuzzFailTest PUBLIC -DTEST_FILE_FOLDER="${TEST_FILE_FOLDER}")
+  target_sources(FuzzFailTest PUBLIC ${PROJECT_SOURCE_DIR}/fuzz/fuzzApp.cpp)
+  if(CLI11_SINGLE_FILE AND CLI11_SINGLE_FILE_TESTS)
+    target_compile_definitions(FuzzFailTest_Single PUBLIC -DTEST_FILE_FOLDER="${TEST_FILE_FOLDER}")
+    target_sources(FuzzFailTest_Single PUBLIC ${PROJECT_SOURCE_DIR}/fuzz/fuzzApp.cpp)
+  endif()
+endif()
+
 # Add -Wno-deprecated-declarations to DeprecatedTest
 set(no-deprecated-declarations $<$<CXX_COMPILER_ID:MSVC>:/wd4996>
                                $<$<NOT:$<CXX_COMPILER_ID:MSVC>>:-Wno-deprecated-declarations>)

tests/FuzzFailTest.cpp

@@ -0,0 +1,37 @@
+// Copyright (c) 2017-2023, University of Cincinnati, developed by Henry Schreiner
+// under NSF AWARD 1414736 and by the respective contributors.
+// All rights reserved.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "../fuzz/fuzzApp.hpp"
+#include "app_helper.hpp"
+
+std::string loadFailureFile(const std::string &type, int index) {
+    std::string fileName(TEST_FILE_FOLDER "/fuzzFail/");
+    fileName.append(type);
+    fileName += std::to_string(index);
+    std::ifstream crashFile(fileName, std::ios::in | std::ios::binary);
+    if(crashFile) {
+        std::vector<char> buffer(std::istreambuf_iterator<char>(crashFile), {});
+
+        std::string cdata(buffer.begin(), buffer.end());
+        return cdata;
+    }
+    return std::string{};
+}
+
+TEST_CASE("app_fail") {
+    CLI::FuzzApp fuzzdata;
+
+    auto app = fuzzdata.generateApp();
+
+    int index = GENERATE(range(1, 3));
+
+    auto parseData = loadFailureFile("fuzz_app_fail", index);
+    try {
+
+        app->parse(parseData);
+    } catch(const CLI::ParseError & /*e*/) {
+    }
+}

tests/NewParseTest.cpp

@@ -305,6 +305,27 @@ template <class X> class objWrapper {
     X val_{};
 };
 
+/// simple class to wrap another  with a very specific type constructor and assignment operators to test out some of the
+/// option assignments
+template <class X> class objWrapperRestricted {
+  public:
+    objWrapperRestricted() = default;
+    explicit objWrapperRestricted(int val) : val_{val} {};
+    objWrapperRestricted(const objWrapperRestricted &) = delete;
+    objWrapperRestricted(objWrapperRestricted &&) = delete;
+    objWrapperRestricted &operator=(const objWrapperRestricted &) = delete;
+    objWrapperRestricted &operator=(objWrapperRestricted &&) = delete;
+
+    objWrapperRestricted &operator=(int val) {
+        val_ = val;
+        return *this;
+    }
+    CLI11_NODISCARD const X &value() const { return val_; }
+
+  private:
+    X val_{};
+};
+
 // I think there is a bug with the is_assignable in visual studio 2015 it is fixed in later versions
 // so this test will not compile in that compiler
 #if !defined(_MSC_VER) || _MSC_VER >= 1910
@@ -347,6 +368,26 @@ TEST_CASE_METHOD(TApp, "doubleWrapper", "[newparse]") {
     CHECK_THROWS_AS(run(), CLI::ConversionError);
 }
 
+TEST_CASE_METHOD(TApp, "intWrapperRestricted", "[newparse]") {
+    objWrapperRestricted<double> dWrapper;
+    app.add_option("-v", dWrapper);
+    args = {"-v", "4"};
+
+    run();
+
+    CHECK(4.0 == dWrapper.value());
+
+    args = {"-v", "thing"};
+
+    CHECK_THROWS_AS(run(), CLI::ConversionError);
+
+    args = {"-v", ""};
+
+    run();
+
+    CHECK(0.0 == dWrapper.value());
+}
+
 static_assert(CLI::detail::is_direct_constructible<objWrapper<int>, int>::value,
               "int wrapper is not constructible from int64");
 

tests/OptionTypeTest.cpp

@@ -336,6 +336,36 @@ TEST_CASE_METHOD(TApp, "pair_check", "[optiontype]") {
     CHECK_THROWS_AS(run(), CLI::ValidationError);
 }
 
+TEST_CASE_METHOD(TApp, "pair_check_string", "[optiontype]") {
+    std::string myfile{"pair_check_file.txt"};
+    bool ok = static_cast<bool>(std::ofstream(myfile.c_str()).put('a'));  // create file
+    CHECK(ok);
+
+    CHECK(CLI::ExistingFile(myfile).empty());
+    std::pair<std::string, std::string> findex;
+
+    auto v0 = CLI::ExistingFile;
+    v0.application_index(0);
+    auto v1 = CLI::PositiveNumber;
+    v1.application_index(1);
+    app.add_option("--file", findex)->check(v0)->check(v1);
+
+    args = {"--file", myfile, "2"};
+
+    CHECK_NOTHROW(run());
+
+    CHECK(myfile == findex.first);
+    CHECK("2" == findex.second);
+
+    args = {"--file", myfile, "-3"};
+
+    CHECK_THROWS_AS(run(), CLI::ValidationError);
+
+    args = {"--file", myfile, "2"};
+    std::remove(myfile.c_str());
+    CHECK_THROWS_AS(run(), CLI::ValidationError);
+}
+
 TEST_CASE_METHOD(TApp, "pair_check_take_first", "[optiontype]") {
     std::string myfile{"pair_check_file2.txt"};
     bool ok = static_cast<bool>(std::ofstream(myfile.c_str()).put('a'));  // create file

tests/fuzzFail/fuzz_app_fail2

@@ -0,0 +1 @@
+1	c	e g0  g0 æß    --tup4 N3CLI10ParseErrorE% 0            %% 0   iÿÿÿÿÿÿÿÿÿÿÿÿÿÿwrap    $