https://bugs.llvm.org/show_bug.cgi?id=45516
Bug ID: 45516
Summary: `error: --rtlib=libgcc requires --unwindlib=libgcc`
emitted twice
Product: clang
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Driver
Assignee: unassignedclangb...@nondot.org
Reporter: i...@maskray.me
CC: llvm-bugs@lists.llvm.org, neeil...@live.com,
richard-l...@metafoo.co.uk
% clang --unwindlib=libunwind /dev/null '-###'
...
clang-11: error: --rtlib=libgcc requires --unwindlib=libgcc
clang-11: error: --rtlib=libgcc requires --unwindlib=libgcc
...
% clang --unwindlib=invalid /dev/null '-###'
...
clang-11: error: invalid unwind library name in argument '--unwindlib=invalid'
clang-11: error: invalid unwind library name in argument '--unwindlib=invalid'
...
clang/lib/Driver/ToolChain.cpp GetUnwindLibType can be called twice. We need to
record whether the diagnostic has been reported to address the issue. Another
idea is to not add -l:libunwind.a or -l:libunwind.so twice.
In the GNU toolchain, libgcc and libgcc_s are duplicated (before and after -lc)
to address the interdependency issue with libc. __absvsi2 may reference abort.
In some GCC configurations, __builtin_trap may call abort. These unneeded
abort/raise calls are the root cause that libgcc libgcc_s or libgcc_eh are
duplicated.
The things around -lc:
gcc exe: -lgcc --as-needed -lgcc_s --no-as-needed
g++ or -shared: -lgcc_s -lgcc
-static or -static-pie: -lgcc -lgcc_eh
In compiler-rt, we may be able to fix these and only add -l:libunwind.{a,so}
once. This can bypass the duplicate diagnostic issue.
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