PkgConfig of protobuf not compatible with CMAKE_BUILD_TYPE=Debug

[andresailer]

What version of protobuf and what language are you using?
Version: 5.25.4
Language: C++

What operating system (Linux, Windows, ...) and version?

Alma Linux 9

What runtime / compiler are you using (e.g., python version or gcc version)
gcc13

What did you do?
Steps to reproduce the behavior:
Configured protobuf with

-D CMAKE_BUILD_TYPE=Debug

And then try linking another project that uses pkgconfig to find protobuf

What did you expect to see

A successfully linked package

What did you see instead?

linker cannot find -lprotobuf

The problem

CMake defines a postfix for debug builds

protobuf/CMakeLists.txt

Lines 54 to 55 in 3ba0709

	set(protobuf_DEBUG_POSTFIX "d"
	CACHE STRING "Default debug postfix")

But the pkgconfig template does not account for this possible postfix

protobuf/cmake/protobuf.pc.cmake

Line 10 in 3ba0709

Libs: -L${libdir} -lprotobuf @CMAKE_THREAD_LIBS_INIT@

[acozzette]

Thank you for the bug report. I don't think we have time to work on this right now but we would be happy to review a pull request if you would like to send us a fix. It seems like we need to fix the pkg-config output to account for this d suffix on debug builds. Or possibly we could consider dropping the special d suffix altogether.