-fno-ident prevents compilers from emitting compiler name and version number information that can needlessly bloat binaries.
For example, in the v0.19.0.1 Windows release binaries, there are > 1000 GCC compiler version strings embedded:
# GCC: (GNU) 7.3-posix 20180312... & GCC: (GNU) 6.3.0 20170415.......
strings bitcoind.exe | rg GCC | wc -l
1021
They end up collected in the end of the.rdata section, and cannot be removed by strip. i.e:
objdump --section=.rdata --full-contents bitcoind.exe
...
cfcc00 00000000 00000000 00000000 00000000 ................
cfcc10 00000000 00000000 00000000 00000000 ................
cfcc20 4743433a 2028474e 55292036 2e332e30 GCC: (GNU) 6.3.0
cfcc30 20323031 37303431 35000000 00000000 20170415.......
cfcc40 4743433a 2028474e 55292037 2e332d70 GCC: (GNU) 7.3-p
cfcc50 6f736978 20323031 38303331 32000000 osix 20180312...
cfcc60 4743433a 2028474e 55292037 2e332d70 GCC: (GNU) 7.3-p
cfcc70 6f736978 20323031 38303331 32000000 osix 20180312...
The flag is available for Clang and GCC.
Relevant code in GCC:
/* Attach a special .ident directive to the end of the file to identify
the version of GCC which compiled this code. The format of the .ident
string is patterned after the ones produced by native SVR4 compilers. */
if (!flag_no_ident)
{
const char *pkg_version = "(GNU) ";
char *ident_str;
if (strcmp ("(GCC) ", pkgversion_string))
pkg_version = pkgversion_string;
ident_str = ACONCAT (("GCC: ", pkg_version, version_string, NULL));
targetm.asm_out.output_ident (ident_str);
}
