Fix Cygwin/MSYS2 CI, ARM64 SSE2 compile failure, and Win32 calling convention mismatch in fast_float plugin

[mm2]

Three CI failures introduced by the Cygwin/MSYS2 build job additions, plus a pre-existing Win32 compile error in the fast_float plugin.

Cygwin CI job (cygwin/install-action → cygwin/cygwin-install-action@v6)

The action name was wrong — cygwin/install-action doesn't exist. Fixed to use the correct cygwin/cygwin-install-action@v6 with explicit install-dir: 'C:\cygwin64' matching the configured shell path.

macOS ARM64 (fast_8_matsh_sse.c including <x86intrin.h>)

LCMS2_DEFINE_CMS_DONT_USE_SSE2=1 was propagated to the main lcms2 library but not to the lcms2_fast_float plugin, causing fast_8_matsh_sse.c to include x86 headers on ARM64. Added the define to the plugin target in Lcms2Plugins.cmake:

if(LCMS2_DEFINE_CMS_DONT_USE_SSE2)
  target_compile_definitions(lcms2_fast_float PRIVATE CMS_DONT_USE_SSE2=1)
endif()

Win32 calling convention (_cmsFree and Formatter_15Bit_Factory)

On 32-bit Windows, CMSEXPORT = __stdcall, but callback typedefs (_cmsFreeUserDataFn, cmsFormatterFactory) use __cdecl. Two issues:

• _cmsFree assigned to _cmsFreeUserDataFn in three files (fast_8_curves.c, fast_float_tethra.c, fast_float_cmyk.c): added an inline __cdecl wrapper _fast_float_free_user_data in fast_float_internal.h.

• Formatter_15Bit_Factory assigned to cmsFormatterFactory in fast_float_sup.c: CMSEXPORT must be kept on the function (it's called directly by fast_float_testbed.c and must be exported from the DLL). Fixed by adding a __cdecl wrapper in fast_float_sup.c that delegates to the __stdcall function:

// Bridges __stdcall (CMSEXPORT) → __cdecl (cmsFormatterFactory)
static cmsFormatter Formatter_15Bit_Factory_wrapper(cmsUInt32Number Type,
                                                    cmsFormatterDirection Dir,
                                                    cmsUInt32Number dwFlags)
{
    return Formatter_15Bit_Factory(Type, Dir, dwFlags);
}

static cmsPluginFormatters PluginFastFloat = {
    { cmsPluginMagicNumber, REQUIRED_LCMS_VERSION, cmsPluginFormattersSig, NULL },
    Formatter_15Bit_Factory_wrapper
};

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[mm2]

@copilot could you check and fix the failing tests?

[Copilot]

@copilot could you check and fix the failing tests?

Fixed in commit 8e04a2d. Three failures were addressed:

1. Cygwin-cmake: Wrong action name cygwin/install-action → cygwin/cygwin-install-action@v6, with install-dir: 'C:\cygwin64' to match the configured shell path.

2. macOS-cmake (arm64): The CMS_DONT_USE_SSE2 compile definition was applied to the main lcms2 library but not to the lcms2_fast_float plugin. On ARM64, SSE2 is unsupported, so fast_8_matsh_sse.c was still trying to include <x86intrin.h>. Added the define to the plugin target in Lcms2Plugins.cmake.

3. Windows-cmake (Win32): On 32-bit Windows, CMSEXPORT = __stdcall, causing calling convention mismatches:

   • _cmsFree (__stdcall) was being assigned to _cmsFreeUserDataFn (__cdecl) in three files. Added a _fast_float_free_user_data cdecl wrapper in fast_float_internal.h.
   • Formatter_15Bit_Factory had CMSEXPORT (__stdcall) but cmsFormatterFactory typedef is __cdecl. Removed CMSEXPORT from that function's declaration and definition.

[mm2]

Ok, it seems the robot got it working this time.