Windows-Clang platform adds -fPIC for shared dlls

Usage
1

Hello. I am compiling on linux host using clang-12 and CMAKE_SYSTEM_NAME Windows-Clang in my toolchain file. I have studied the Modules/Platform/Windows-Clang.cmake which makes a decission on choosing msvc/gnu variant basing on CMAKE_C_SIMULATE_ID and CMAKE_CXX_SIMULATE_ID variables. Setting them to “MSVC” makes the static libs and executables build succefully EXCEPT for dlls, with error

clang-12: unsupported option '-fPIC' for target i386-pc-windows-msvc

But the thing is this flag is not being set anywhere… there even are comments in the Windows toolchains:

Windows-Clang.cmake:37:  # No -fPIC on Windows
Windows-GNU.cmake:68:  # No -fPIC on Windows

So where does this -fPIC come from??
For now it is enough to sed after cmake project files generation to remove this flag from compile line and entire projects builds and runs.

2

Position Independent Code (PIC) is enabled by default for SHARED libraries. You can set CMAKE_POSITION_INDEPENDENT_CODE to False in order to disable that behavior.

3

That was it! :slight_smile:

4

That sounds like more like a hack, not like a solution.

5

The CMAKE_SYSTEM_NAME should be Windows, not Windows-Clang.

6

You may be right but I’ve went through so much of steps i do not remember what exactly was wrong with WIndows. I think it was assumming mingw ABI/commandline which is incompatible with clang, but i dont have will to dig right now.