percent signs in target_compile_definitions on Windows

Consider a target with compile definitions like this

target_compile_definitions(myapp PRIVATE

This works fine on Linux, but on Windows there will be errors. For example, MSVC’s cl.exe yields “cl : Command line error D8038 : invalid argument”.

According to MS docs at /D (Preprocessor Definitions) | Microsoft Docs percent sign should be written as doubled percent sign when passing it to the compiler with -D.

A more thorough explanation of the issue can be found in this blog post: Percent-sign in preprocessor definition breaks CMake Visual Studio generator

Given that target_compile_definitions already does some escaping, should it also take care of doubling the percent sign on Windows?

Yes, this sounds like something that CMake should be doing. Please file an issue.