GDB: DebugInfo

Binary with DebugInfo

Build binary with debug info.

  gcc -g ...
  g++ -g ...

List sections using objdump.

  objdump --section-headers binary


Sample: Build binary with debuginfo.

int sum(int a, int b)
{
    return a + b;
}

int main()
{
    sum(1, 2);
}
  
#-------------------------------
gcc -g demo.c -o demo

objdump --section-headers demo
#-------------------------------

Binary with debuginfo.

0.  note.gnu.build-id
1.  interp
2.  gnu.hash
3.  dynsym
4.  dynstr
5.  gnu.version
6.  gnu.version_r
7.  rela.dyn
8.  rela.plt
9.  init
10. plt
11. text
12. fini
13. rodata
14. eh_frame_hdr
15. eh_frame
16. note.ABI-tag
17. init_array
18. fini_array
19. dynamic
20. got
21. got.plt
22. data
23. bss
24. comment
25. annobin.notes
26. gnu.build.attributes
#-----------------------
27. debug_aranges
28. debug_info
29. debug_abbrev
30. debug_line
31. debug_str
32. debug_line_str

Split DebugInfo

GDB allows to split the debuginfo of a binary into a separate file. The purpose is to optimize binary size. When debugging is needed later, the debug information can be reattached.

Extract debuginfo into a file.

  objcopy --only-keep-debug binary debuginfo

Remove debuginfo from binary.

  strip --strip-debug binary


Sample: Strip a binary.

#-------------------------------
gcc -g demo.c -o demo

objcopy --only-keep-debug demo demo.debuginfo
strip --strip-debug demo

objdump --section-headers demo
#-------------------------------

Without debuginfo.

0.  note.gnu.build-id
1.  interp
2.  gnu.hash
3.  dynsym
4.  dynstr
5.  gnu.version
6.  gnu.version_r
7.  rela.dyn
8.  rela.plt
9.  init
10. plt
11. text
12. fini
13. rodata
14. eh_frame_hdr
15. eh_frame
16. note.ABI-tag
17. init_array
18. fini_array
19. dynamic
20. got
21. got.plt
22. data
23. bss
24. comment
25. annobin.notes
26. gnu.build.attributes

Attach DebugInfo

Creates a .gnu_debuglink section which contains a reference to debuginfo file and adds it to the binary file.

  objcopy --add-gnu-debuglink=debuginfo binary


Sample: Attach debuginfo to binary

objcopy --add-gnu-debuglink=demo.debuginfo demo

With debuglink.

0.  note.gnu.build-id
1.  interp
2.  gnu.hash
..  .....
24. comment
25. annobin.notes
26. gnu.build.attributes
#-----------------------
27. gnu_debuglink

Search Directory

Default, GDB searches for debuginfo files in the below directories.

However, we can change the search directories.

  set debug-file-directory dirs
  show debug-file-directory