Hi, consider the following MWE: |$ touch bar/foo.h $ cat bar/main.cpp #include "foo.h" int main(){} With this most simple setup calling GCC with `g++ "bar\main.cpp"` results in GCC failing to find the include file. However using `g++ "bar/main.cpp"` works as expected. | |So the compiler does find the CPP file and also is able to resolve others paths passed with backslashes (e.g. -I arguments) but basically disables resolving includes relative to the file including it. For context: This turned up on CI for Boost where "|C:\cygwin64\bin" is added to the PATH env variable to be able to use the Cygwin GCC with B2. The build system, finding it is running on Windows, will pass paths with backward slashes to the compiler. This happens on both CMD with the added PATH and using the bash. For reference I tried the same with MinGW and there either path separator worked. So it seems to be an issue in the Cygwin builds of GCC. I tried both 11.2 and 11.3, the latest currently available. Best Regards, Alexander Grund ||