Fix compiler errors from check third-party dependency on Windows

[sbmueller]

Issue

The check unit testing framework (used as a third-party dependency) emits compiler diagnostics that break the build on Windows platforms, even though it's configured as an external dependency with SYSTEM_INCLUDES.

Specific error:

D:\a\libsbp\libsbp\c\third_party\check\lib\timer_delete.c:48:5: error: implicit declaration of function 'alarm' [-Wimplicit-function-declaration]

Root Cause

The check library has platform compatibility issues on Windows:

1. Missing POSIX functions: Windows lacks POSIX functions like alarm(), setitimer(), and proper timer support
2. Incomplete fallback detection: While check includes compatibility shims (e.g., alarm.c), the file timer_delete.c calls alarm() directly without proper header inclusion or declaration checking
3. SYSTEM_INCLUDES limitation: The SYSTEM_INCLUDES flag in CMake only suppresses warnings from headers consumed via target_include_directories(). However, check adds its compatibility source files (including timer_delete.c) directly to the target via target_sources(), so these files are compiled as part of the target itself and inherit all parent compile flags including -Werror

Note: The check project has been unmaintained for over 4 years (last release: 0.15.2 in 2020), making an upstream fix unlikely.

Solution

Modified cmake/common/FindCheck.cmake to temporarily adjust CMAKE_C_FLAGS during the check library's configuration and compilation:

1. Save original flags before including the dependency
2. Apply platform-specific suppressions:

• MinGW/GCC: Remove -Werror and add -Wno-error=implicit-function-declaration
• MSVC: Remove /WX and add /wd4013 (disables C4013: implicit function declaration)

3. Restore original flags immediately after the dependency is added

This approach:

• ✅ Doesn't modify third-party code
• ✅ Only affects check library compilation
• ✅ Preserves strict warnings for project code
• ✅ Supports both MinGW and MSVC toolchains

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[martin4861]

lgtm! Thanks for fixing!

[jakalm]

LGTM!