Re: [PATCH perf-tools-next] perf list: Avoid repeated strlen when escaping JSON strings

The %S conversion in fix_escape_fprintf() calls strlen(s) in the loop
condition while escaping each character. GCC 14.2.0 retains this call
inside the loop in a normal DEBUG=0 (-O3) perf build, repeatedly scanning
the whole string.

Test the current character for NUL instead. This processes the same bytes
without rescanning the string. Escaping and buffer growth are unchanged.

Full-command wall-clock measurements on an Apple M5 Pro host running an
aarch64 Linux container with GCC 14.2.0 and glibc 2.41 gave these medians:

  perf list --json metrics       Before (ms)  After (ms)
  Default catalog                    0.5969      0.5855
  PERF_CPUID=0x00000000410fd830        0.7818      0.7033

[ ... ]
Codex assisted with identifying the redundant scan, preparing the change,
and running the comparisons.

Assisted-by: LLM
Signed-off-by: Qerogram <redacted>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260910123839.72285-1-qerogram@naver.com?part=1