test-lib: add a few comments to LSan log checking

Commit b119a687d4 (test-lib: ignore leaks in the sanitizer's thread
code, 2025-01-01) added code to suppress a false positive in the leak
checker. But if you're just reading the code, the obscure grep call is a
bit of a head-scratcher. Let's add a brief comment explaining what's
going on (and anybody digging further can find this commit or that one
for all the details).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/test-lib.sh b/t/test-lib.sh
index 898c2267b8a400db91e919f3169e0982f9fba7e4..9f27a49995160e885fc5f31474f82c37c41c3fb8 100644 (file)
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1172,6 +1172,11 @@ test_atexit_handler () {
 check_test_results_san_file_has_entries_ () {
        test -z "$TEST_RESULTS_SAN_FILE" && return 1
 
+       # Lines marked with DEDUP_TOKEN show unique leaks. We only care that we
+       # found at least one.
+       #
+       # But also suppress any false positives caused by bugs or races in the
+       # sanitizer itself.
        grep -s ^DEDUP_TOKEN "$TEST_RESULTS_SAN_FILE".* |
        grep -qv sanitizer::GetThreadStackTopAndBottom
 }