fail builds in CI on compiler warnings

.github/workflows/CI-unixish.yml

@@ -30,10 +30,18 @@ jobs:
       run: |
         sudo apt-get update
         sudo apt-get install libc++-18-dev
-
+
+    # coreutils contains "nproc"
+    - name: Install missing software on macos
+      if: contains(matrix.os, 'macos')
+      run: |
+        brew install coreutils
+
+    # TODO: bail out on warning
     - name: make simplecpp
       run: make -j$(nproc)
 
+    # TODO: bail out on warning
     - name: make test
       run: make -j$(nproc) test
 
@@ -43,7 +51,7 @@ jobs:
 
     - name: Run CMake
       run: |
-        cmake -S . -B cmake.output
+        cmake -S . -B cmake.output -DCMAKE_COMPILE_WARNING_AS_ERROR=On
 
     - name: CMake simplecpp
       run: |
@@ -66,31 +74,31 @@ jobs:
       if: matrix.os == 'ubuntu-24.04' && matrix.compiler == 'g++'
       run: |
         make clean
-        make -j$(nproc) test selfcheck CXXFLAGS="-g3 -D_GLIBCXX_DEBUG"
+        make -j$(nproc) test selfcheck CXXFLAGS="-Werror -Wno-multichar -g3 -D_GLIBCXX_DEBUG"
 
     - name: Run with libc++ hardening mode
       if: matrix.os == 'ubuntu-24.04' && matrix.compiler == 'clang++'
       run: |
         make clean
-        make -j$(nproc) test selfcheck CXXFLAGS="-stdlib=libc++ -g3 -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_DEBUG" LDFLAGS="-lc++"
+        make -j$(nproc) test selfcheck CXXFLAGS="-Werror -Wno-multichar -stdlib=libc++ -g3 -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_DEBUG" LDFLAGS="-lc++"
 
     - name: Run AddressSanitizer
       if: matrix.os == 'ubuntu-24.04'
       run: |
         make clean
-        make -j$(nproc) test selfcheck CXXFLAGS="-O2 -g3 -fsanitize=address" LDFLAGS="-fsanitize=address"
+        make -j$(nproc) test selfcheck CXXFLAGS="-Werror -Wno-multichar -O2 -g3 -fsanitize=address" LDFLAGS="-fsanitize=address"
       env:
         ASAN_OPTIONS: detect_stack_use_after_return=1
 
     - name: Run UndefinedBehaviorSanitizer
       if: matrix.os == 'ubuntu-24.04'
       run: |
         make clean
-        make -j$(nproc) test selfcheck CXXFLAGS="-O2 -g3 -fsanitize=undefined -fno-sanitize=signed-integer-overflow" LDFLAGS="-fsanitize=undefined -fno-sanitize=signed-integer-overflow"
+        make -j$(nproc) test selfcheck CXXFLAGS="-Werror -Wno-multichar -O2 -g3 -fsanitize=undefined -fno-sanitize=signed-integer-overflow" LDFLAGS="-fsanitize=undefined -fno-sanitize=signed-integer-overflow"
 
     # TODO: requires instrumented libc++
     - name: Run MemorySanitizer
       if: false && matrix.os == 'ubuntu-24.04' && matrix.compiler == 'clang++'
       run: |
         make clean
-        make -j$(nproc) test selfcheck CXXFLAGS="-O2 -g3 -stdlib=libc++ -fsanitize=memory" LDFLAGS="-lc++ -fsanitize=memory"
+        make -j$(nproc) test selfcheck CXXFLAGS="-Werror -Wno-multichar -O2 -g3 -stdlib=libc++ -fsanitize=memory" LDFLAGS="-lc++ -fsanitize=memory"

.github/workflows/CI-windows.yml

@@ -30,16 +30,18 @@ jobs:
       - name: Run cmake
         if: matrix.os == 'windows-2019'
         run: |
-          cmake -G "Visual Studio 16 2019" -A x64 . || exit /b !errorlevel!
+          cmake -G "Visual Studio 16 2019" -A x64 -DCMAKE_COMPILE_WARNING_AS_ERROR=On . || exit /b !errorlevel!
 
       - name: Run cmake
         if: matrix.os == 'windows-2022'
         run: |
-          cmake -G "Visual Studio 17 2022" -A x64 . || exit /b !errorlevel!
+          cmake -G "Visual Studio 17 2022" -A x64 -DCMAKE_COMPILE_WARNING_AS_ERROR=On . || exit /b !errorlevel!
 
       - name: Build
         run: |
            msbuild -m simplecpp.sln /p:Configuration=${{ matrix.config }} /p:Platform=x64 || exit /b !errorlevel!
+        env:
+          _CL_: /WX
 
       - name: Test
         run: |

.github/workflows/clang-tidy.yml

@@ -30,7 +30,7 @@ jobs:
 
       - name: Prepare CMake
         run: |
-          cmake -S . -B cmake.output -G "Unix Makefiles" -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DDISABLE_CPP03_SYNTAX_CHECK=ON
+          cmake -S . -B cmake.output -G "Unix Makefiles" -DCMAKE_COMPILE_WARNING_AS_ERROR=On -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DDISABLE_CPP03_SYNTAX_CHECK=ON
         env:
           CXX: clang-19
 

CMakeLists.txt

@@ -20,6 +20,7 @@ endfunction()
 
 if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
     add_compile_options(-Wall -Wextra -pedantic -Wcast-qual -Wfloat-equal -Wmissing-declarations -Wmissing-format-attribute -Wredundant-decls -Wshadow -Wundef -Wold-style-cast -Wno-multichar)
+    add_compile_options(-Wno-shadow) # TODO: fix these
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
     add_compile_definitions(_CRT_SECURE_NO_WARNINGS)
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
@@ -38,6 +39,10 @@ elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     # TODO: fix these?
     add_compile_options(-Wno-padded -Wno-sign-conversion -Wno-implicit-int-conversion -Wno-shorten-64-to-32 -Wno-shadow-field-in-constructor)
 
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
+        add_compile_options(-Wno-c++11-long-long)
+    endif()
+
     if (CMAKE_CXX_COMPILER_VERSION VERSION_EQUAL 14 OR CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 14)
         # TODO: verify this regression still exists in clang-15
         if (CMAKE_BUILD_TYPE STREQUAL "Release" OR CMAKE_BUILD_TYPE STREQUAL "RelWithDebInfo")