[PATCH] D95927: DebugInfo/Symbolize: Retrieve filename from the preceding STT_FILE for .symtab symbolization

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
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The ELF spec says:

> STT_FILE: Conventionally, the symbol's name gives the name of the source file associated with the object file. A file symbol has STB_LOCAL binding, its section index is SHN_ABS, and it precedes the other STB_LOCAL symbols for the file, if it is present.

For a local symbol, the preceding STT_FILE symbol is almost always in the same
file[1]. GNU addr2line uses this heuristic to retrieve the filename associated
with a local symbol (e.g. internal linkage functions in C/C++).

In case of filename mismatch between .debug_line & .symtab, arbitrarily make .debug_line win.

[1]: LLD does not synthesize STT_FILE symbols
(https://bugs.llvm.org/show_bug.cgi?id=48023 see also
https://sourceware.org/bugzilla/show_bug.cgi?id=26822).  An assembly file
without `.file` directives can cause mis-attribution. This is an edge case.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D95927

Files:
  llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp
  llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.h
  llvm/test/DebugInfo/Symbolize/ELF/symtab-file.yaml
  llvm/test/DebugInfo/Symbolize/ELF/symtab-notype.s

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