D13550 added the diagnostic to address/work around a crash.
The rule was refined by D19836 (test/ELF/tls-archive.s) to exclude Lazy symbols.
https://bugs.llvm.org/show_bug.cgi?id=45598 reported another case where the current logic has a false positive:
Bitcode does not record undefined module-level inline assembly symbols
(`IRSymtab.cpp:Builder::addSymbol`). Such an undefined symbol does not
have the FB_tls bit and lld will not consider it STT_TLS. When the symbol is
later replaced by a STT_TLS Defined, lld will error "TLS attribute mismatch".
This patch fixes this false positive by allowing a STT_NOTYPE undefined
symbol to be replaced by a STT_TLS.
Considered alternative:
Moving the diagnostics to scanRelocs() can improve the diagnostics (PR36049)
but that requires a fair amount of refactoring. We will need more
RelExpr members. It requires more thoughts whether it is worthwhile.
See `test/ELF/tls-mismatch.s` for behavior differences. We will fail to
diagnose a likely runtime bug (STT_NOTYPE non-TLS relocation referencing
a TLS definition). This is probably acceptable because compiler
generated code sets symbol types properly.
Reviewed By: grimar, psmith
Differential Revision: https://reviews.llvm.org/D78438
This patch is intended to improve readability of "duplicate symbol"
error messages.
Without this patch:
/ssd/clang/bin/ld.lld: error: /ssd/llvm-project/lld/ELF/Relocations.cpp:1054: duplicate symbol 'lld:🧝:demangle(llvm::StringRef)'
/ssd/clang/bin/ld.lld: error: /ssd/llvm-project/lld/ELF/Strings.cpp:93: previous definition was here
With this patch:
/ssd/clang/bin/ld.lld: error: duplicate symbol: lld:🧝:demangle(llvm::StringRef)
>>> defined at Strings.cpp:93 (/ssd/llvm-project/lld/ELF/Strings.cpp:93)
>>> Strings.cpp.o:(lld:🧝:demangle(llvm::StringRef)) in archive lib/liblldELF.a
>>> defined at Relocations.cpp:1054 (/ssd/llvm-project/lld/ELF/Relocations.cpp:1054)
>>> Relocations.cpp.o:(.text+0x4C30) in archive lib/liblldELF.a
Discussion thread:
http://lists.llvm.org/pipermail/llvm-dev/2017-March/111459.html
Differential Revision: https://reviews.llvm.org/D31507
llvm-svn: 299280
Fangrui Song