I’m (semi-)maintaining a private copy of pthreads4w, which is one of those libraries which uses one “.c” file and different definitions to output several variants of the library. One variant uses C++ exceptions to clean up threads, and when I last used 3.14, I could use:
This would allow the one specific target to compile pthread.c as if it were C++ code. CMake 3.18 seems to really insist on having the MSVC “/TC” flag on the command line, completely ignoring my target_compile_options.
The regression, issue, and fix Ben mentioned were all in the 3.19 series.
To answer the original question, don’t try to use /TP directly. You need to tell CMake that you want the file treated as C++ by setting the LANGUAGE source file property to CXX. There is also ongoing work to make that work in more cases.
Meanwhile, I suggest creating a pthread.cxx that just has #include "pthread.c", and list pthread.cxx as the source instead.
Brad: I think we resolved this on the gitlab issue tracker and I decided to take the #include route.
One problem with the LANGUAGE approach: It’s a property that’s inspected at generation time. Consequently, if one sets LANGUAGE for foo.c in target_a as “C”, then set LANGUAGE as “CXX” in target_b, then target_a will compile foo.c as “CXX”.
That’s the reason why I suggested making LANGUAGE a target-specific property.
I agree that /TP is a hack, but it was one that worked for a long time.
