System-headers-only harness timing the five L1 string functions
(strlen, strcmp, memcpy, memmove, memset) at 8- and 64-byte inputs.
Calls go through volatile function pointers to defeat builtin
substitution and LICM hoisting; correctness self-asserts route through
the same pointers. Prints FUNC@SIZE ns/call lines.
bench_string uses empty per-target CPPFLAGS (no -I include) so it links
against whichever libc --with-libc= selects; the bench target runs it
always and bench_vlibc only under BENCH_LINK_VLIBC. Both programs
relink when config.status changes, so a reconfigure cannot silently
reuse a binary from the previous libc.
Measured vs glibc 2.44 (median of 3 runs): mem* 1.0-3.3x,
strlen/strcmp 3.2-3.9x — word-at-a-time vs AVX2, all sane.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <[email protected]>
