[LLD] [COFF] Add a separate option for allowing duplicate weak symbols #68077
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The MinGW mode (enabled with the flag -lldmingw) does allow duplicate weak symbols. A test in compiler-rt/test/profile/Windows/coverage-weak-lld.cpp does currently enable the -lldmingw flag in an MSVC context, in order to deal with duplicate weak symbols. Add a new, separate, lld specific flag for enabling this. In MinGW mode, this is enabled by default, otherwise it is disabled. This allows making the MinGW mode more restrictive in adding libpaths from the surrounding environment; in MinGW mode, all libpaths are passed explicitly by the compiler driver to the linker, which is attempted in https://reviews.llvm.org/D144084.
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@MaskRay This relates to the use of |
I added the test in in 2021 when investigating Windows's weak symbols: https://maskray.me/blog/2021-04-25-weak-symbol#pecoff I haven't added similar tests elsewhere. Thank you for making a standalone option. I wonder whether anyone has a channel to tell MSVC that this is a desired feature that should be enabled by default. |
| RUN: lld-link -lld-allow-duplicate-weak %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe | ||
| RUN: not lld-link %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe 2>&1 | FileCheck %s --check-prefix=DEFAULT-ERROR | ||
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| DEFAULT-ERROR: error: duplicate symbol: weakfunc |
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If this is the last line, consider adding DEFAULT-ERROR-NOT: {{.}} as a change detector when the diagnostic improves.
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There are more lines following this diagnostic (defined at /path/to/object/file), so I'll leave this as is.
Ok, thanks for the info!
I guess one could post a feature request at https://developercommunity.visualstudio.com/cpp; I'm not very hopeful that it'd be implemented, but it would at least be the official way of signaling the request. |
In mingw mode, all linker paths are passed explicitly to the linker by the compiler driver. Don't try to implicitly add linker paths from the LIB environment variable or by detecting an MSVC installation directory. If the /winsysroot command line parameter is explicitly passed to lld-link while /lldmingw is specified, it could be considered reasonable to actually include those paths. However, modifying the code to handle only the /winsysroot case but not the other ones, when the mingw mode has been enabled, seems like much more code complexity for a mostly hypothetical case. Add a test for this when case when using LIB. (The code paths for trying to detect an MSVC installation aren't really regression tested.) Also fix an issue in the existing test for "Check that when /winsysroot is specified, %LIB% is ignored.", where the LIB variable pointed to a nonexistent directory, so the test would pass even if /winsysroot wouldn't be specified. Reland this after #68077 and #69781 - the compiler-rt test that used -lldmingw in MSVC environments has been updated to use a more specific option. Differential Revision: https://reviews.llvm.org/D144084
llvm#68077) The MinGW mode (enabled with the flag -lldmingw) does allow duplicate weak symbols. A test in compiler-rt/test/profile/Windows/coverage-weak-lld.cpp does currently enable the -lldmingw flag in an MSVC context, in order to deal with duplicate weak symbols. Add a new, separate, lld specific flag for enabling this. In MinGW mode, this is enabled by default, otherwise it is disabled. This allows making the MinGW mode more restrictive in adding libpaths from the surrounding environment; in MinGW mode, all libpaths are passed explicitly by the compiler driver to the linker, which is attempted in https://reviews.llvm.org/D144084.
The MinGW mode (enabled with the flag -lldmingw) does allow duplicate weak symbols. A test in
compiler-rt/test/profile/Windows/coverage-weak-lld.cpp does currently enable the -lldmingw flag in an MSVC context, in order to deal with duplicate weak symbols.
Add a new, separate, lld specific flag for enabling this. In MinGW mode, this is enabled by default, otherwise it is disabled.
This allows making the MinGW mode more restrictive in adding libpaths from the surrounding environment; in MinGW mode, all libpaths are passed explicitly by the compiler driver to the linker, which is attempted in https://reviews.llvm.org/D144084.