1. test_plocks.c: add comment to test_upgrade_under_contention clarifying
it verifies towrlock completion and holding_wrlock; notes that concurrent
exclusivity is covered by test_stress().
2. test_pfsupload.c / make_fake_api: replace static-local psock_t with
caller-supplied stack allocation (out parameter) to eliminate the
multiple-calls-per-test footgun.
3. test_pfsupload.c / find_str_param: replace ternary
`paramnamelen == strlen ? paramname : ""` with explicit length check +
strncmp, matching the cleaner pattern used in find_num_param.
4. Makefile: add comment next to -Wl,--wrap=papi_send noting it redirects
papi_send to __wrap_papi_send and is GNU ld only (not macOS Apple ld).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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