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llvm-mirror/test/DebugInfo/Symbolize/ELF/symtab-file2.yaml
Fangrui Song 16779dce78 DebugInfo/Symbolize: Retrieve filename from the preceding STT_FILE for .symtab symbolization
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++).

GNU addr2line can assign STT_FILE filename to a non-local symbol, too, but the trick
only works if no regular symbol precede STT_FILE. This patch does not implement this corner case
(not useful for most executables which have more than one files).

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.

Differential Revision: https://reviews.llvm.org/D95927
2021-02-10 09:47:10 -08:00

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1.8 KiB
YAML

# RUN: yaml2obj --docnum=1 %s -o %t1
# RUN: llvm-symbolizer --obj=%t1 0 1 2 | FileCheck %s
## The local symbol has no preceding STT_FILE. Its filename is unavailable.
# CHECK: local
# CHECK-NEXT: ??:0:0
# CHECK-EMPTY:
## All local symbols precede all non-local symbols. When there are multiple
## STT_FILE symbols, we cannot tell which file defines the non-local symbol in
## question. We could tell if there is only one STT_FILE but in reality there
## are always more than one file, so implementing the special case is not useful.
# CHECK-NEXT: global
# CHECK-NEXT: ??:0:0
# CHECK-EMPTY:
# CHECK-NEXT: weak
# CHECK-NEXT: ??:0:0
# CHECK-EMPTY:
--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_DYN
Machine: EM_X86_64
Sections:
- Name: .text
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
Size: 3
Symbols:
- Name: local
Section: .text
Value: 0
- Name: 1.c
Type: STT_FILE
Index: SHN_ABS
- Name: global
Binding: STB_GLOBAL
Section: .text
Value: 1
- Name: weak
Binding: STB_WEAK
Section: .text
Value: 2
## If st_name of the STT_FILE symbols is invalid, the symbol name is lost as well.
## TODO Keep the symbol name.
# RUN: yaml2obj --docnum=2 %s -o %t2
# RUN: llvm-symbolizer --obj=%t2 0 0 2>&1 | FileCheck %s --check-prefix=CHECK2
# CHECK2: error reading file: st_name (0xffff) is past the end of the string table of size
# CHECK2-NEXT: ??
# CHECK2-NEXT: ??:0:0
# CHECK2-EMPTY:
# CHECK2-NEXT: ??
# CHECK2-NEXT: ??:0:0
--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_DYN
Machine: EM_X86_64
Sections:
- Name: .text
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
Size: 1
Symbols:
- StName: 0xffff
Type: STT_FILE
Index: SHN_ABS
- Name: local
Section: .text