symbol table VS debug symbols

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symbol table : one symbol is a address of data or function.

debug symbol : A debug symbol is a special kind of symbol that attaches additional information to the symbol table of an object file.

So, debug symbol is entry in the symbol table.

view symbol table

objdump -t

tt@ZHANGKAIWEN01:~$ objdump a.out -t

a.out:     file format elf64-x86-64

SYMBOL TABLE:
0000000000000318 l    d  .interp        0000000000000000              .interp
0000000000000338 l    d  .note.gnu.property     0000000000000000              .note.gnu.property
0000000000000358 l    d  .note.gnu.build-id     0000000000000000              .note.gnu.build-id
000000000000037c l    d  .note.ABI-tag  0000000000000000              .note.ABI-tag
...
...
# no .debug*** in symbol table, if build with `gcc hello.c`
tt@xxx:~$ objdump -t a.out | grep debug
tt@xxx:~$

view debug symbols, build with gcc -g ***

grep .debug in symbol table

tt@xxx:~$ objdump a.out -t | grep .debug
0000000000000000 l    d  .debug_aranges 0000000000000000              .debug_aranges
0000000000000000 l    d  .debug_info    0000000000000000              .debug_info
0000000000000000 l    d  .debug_abbrev  0000000000000000              .debug_abbrev
0000000000000000 l    d  .debug_line    0000000000000000              .debug_line
0000000000000000 l    d  .debug_str     0000000000000000              .debug_str

Check if there is a debug symbol using file command

# no debug symbols, build with `gcc hello.c`
tt@xxx:~$ file a.out
a.out: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=30bd96750c22e4e2f8ff3e214318aa17dc80a900, for GNU/Linux 3.2.0, not stripped

# there is debug symbols, build with `gcc hello.c -g`
tt@xxx:~$ file a.out
a.out: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=a1c6d8cf4ac556b017cd1de27cba47f98dd0ac25, for GNU/Linux 3.2.0, with debug_info, not stripped