[CMake] Localize a build hack #12895
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The '-Wl,-z,defs' flag is useful, so let's disable it only where needed.
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@swift-ci please smoke test |
| # into swift. The use of this flag pollutes all targets, and we are not able | ||
| # to remove it on a per-target basis which breaks cross-compilation. | ||
| string(REGEX REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}") | ||
| if("${CMAKE_SYSTEM_NAME}" STREQUAL "Windows") |
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This is wrong. This flag only comes in cross compiling. The CMAKE_SYSTEM_NAME is UNIX.
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I'm happy to refine this. What is the right way to check for Windows in this case?
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You cannot at this level, hence I was suggesting that we sink this further. Pushing this into the add_library call would be sufficiently low that we can check the target for the library being built.
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Is it really necessary on Windows to modify add_library? What specific Swift binaries need this flag removed? For example, on Linux only SwiftRemoteMirror "needs" the flag removed, and after I looked into the scenario, I'm convinced that -Wl,-z,defs is correctly identifying a bug, so removing the flag only makes the problem worse, not better.
Rather than add infrastructure to formalize the removal of -Wl,-z,defs, it seems better/wiser to contain the problem to the affected libraries until they can be cleaned up.
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Yes, it really is necessary to modify add_library. The point is that we are sharing the flags incorrectly. The flag is for build not for host when cross-compiling. Im compiling a compiler for Linux and the stdlib and tests for Windows. The flags are not valid for the host, but are valid for the build. It is any library that is going to run on the host that needs the alteration. This would include things like the stdlib, the runtime, SwiftDemangle, SwiftRemoteMirror, etc.
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The '-Wl,-z,defs' flag is useful, so let's disable it only where needed.