[release/5.0] Re-enable support for using the system libunwind #42853
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We can now build runtime against the system libunwind using:
./build.sh -cmakeargs -DCLR_CMAKE_USE_SYSTEM_LIBUNWIND
This allows Linux distributions that already ship a compatible version
of libunwind library to use that instead of carrying a duplicate in
.NET. This provides some benefits to them, including smaller build
sizes, slightly faster builds and fewer places to fix any
vulnerabilities
This functionality was already supported in .NET Core 3.1 and has
regressed since.
CoreCLR already handles `-DCLR_CMAKE_USE_SYSTEM_LIBUNWIND`, so no
changes are needed there.
The libraries build doesn't care about this cmake varibale, but cmake
itself fails if the variable is not used:
EXEC : CMake error : [runtime/src/libraries/Native/build-native.proj]
Manually-specified variables were not used by the project:
CLR_CMAKE_USE_SYSTEM_LIBUNWIND
So libraries just needs to check and ignore this variable.
The singlefilehost needs to link against libunwind too. Otherwise the
linker fails to resolve symbols, making the build fail:
/usr/bin/ld: runtime/artifacts/bin/coreclr/Linux.x64.Debug//lib/libcoreclrpal.a(seh.cpp.o): in function `UnwindContextToWinContext(unw_cursor*, _CONTEXT*)':
dotnet/runtime/src/coreclr/src/pal/src/exception/seh-unwind.cpp:176: undefined reference to `_ULx86_64_get_reg'
/usr/bin/ld: runtime/src/coreclr/src/pal/src/exception/seh-unwind.cpp:177: undefined reference to `_ULx86_64_get_reg'
/usr/bin/ld: runtime/src/coreclr/src/pal/src/exception/seh-unwind.cpp:178: undefined reference to `_ULx86_64_get_reg'
/usr/bin/ld: runtime/src/coreclr/src/pal/src/exception/seh-unwind.cpp:179: undefined reference to `_ULx86_64_get_reg'
/usr/bin/ld: runtime/src/coreclr/src/pal/src/exception/seh-unwind.cpp:180: undefined reference to `_ULx86_64_get_reg'
/usr/bin/ld: runtime/artifacts/bin/coreclr/Linux.x64.Debug//lib/libcoreclrpal.a(seh.cpp.o): runtime/src/coreclr/src/pal/src/exception/seh-unwind.cpp:181: more undefined references to `_ULx86_64_get_reg' follow
/usr/bin/ld: runtime/artifacts/bin/coreclr/Linux.x64.Debug//lib/libcoreclrpal.a(seh.cpp.o): in function `GetContextPointer(unw_cursor*, ucontext_t*, int, unsigned long**)':
runtime/src/coreclr/src/pal/src/exception/seh-unwind.cpp:227: undefined reference to `_ULx86_64_get_save_loc'
/usr/bin/ld: runtime/artifacts/bin/coreclr/Linux.x64.Debug//lib/libcoreclrpal.a(seh.cpp.o): in function `PAL_VirtualUnwind':
runtime/src/coreclr/src/pal/src/exception/seh-unwind.cpp:340: undefined reference to `_ULx86_64_init_local'
/usr/bin/ld: runtime/src/coreclr/src/pal/src/exception/seh-unwind.cpp:351: undefined reference to `_ULx86_64_step'
/usr/bin/ld: runtime/src/coreclr/src/pal/src/exception/seh-unwind.cpp:360: undefined reference to `_ULx86_64_is_signal_frame'
clang-10: error: linker command failed with exit code 1 (use -v to see invocation)
Fixes: #42661
VSadov
approved these changes
Sep 29, 2020
This was referenced Sep 29, 2020
|
@jeffschwMSFT This has already been approved, right? |
|
@agocke once we have verified and feel this is good, we can merge as part of tell mode for GA. |
jeffschwMSFT
approved these changes
Oct 1, 2020
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Backport of #42689 to release/5.0
/cc @agocke @omajid
Customer Impact
Source build uses the system libunwind, so without this change the singlefilehost cannot build.
Testing
source build has been tested with the change, and succeeds.
Risk
Low, passing existing options for the CoreCLR build to the singlefilehost build in the same way.