[PATCH 06/10] test-lib: add a SANITIZE=leak logging mode

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Add the ability to run the test suite under a new
"GIT_TEST_SANITIZE_LEAK_LOG=true" mode, when true we'll log the leaks
we find an a new "test-results/<test-name>.leak" directory.

That new path is consistent with the existing
"test-results/<test-name>.<type>" results, except that those are all
files, not directories.

We also set "log_exe_name=1" to include the name of the executable in
the filename. This gives us files like "trace.git.<pid>" instead of
the default of "trace.<pid>". I.e. we'll be able to distinguish "git"
leaks from "test-tool", "git-daemon" etc.

We then set "dedup_token_length" to non-zero ("0" is the default) to
succinctly log a token we can de-duplicate these stacktraces on. The
string is simply a one-line stack-trace with only function names up to
N frames, which we limit at "9999" as a shorthand for
"infinite" (there appears to be no way to say "no limit").

With these combined we can now easily get e.g. the top 10 leaks in the
test suite grouped by full stacktrace:

    grep -o -P -h '(?<=DEDUP_TOKEN: ).*' test-results/*.leak/trace.git.* | sort | uniq -c | sort -nr | head -n 10

Or add "grep -E -o '[^-]+'" to that to group by functions instead of
stack traces:

    grep -o -P -h '(?<=DEDUP_TOKEN: ).*' test-results/*.leak/trace.git.* | grep -E -o '[^-]+' | sort | uniq -c | sort -nr | head -n 20

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 t/README      |  6 ++++++
 t/test-lib.sh | 21 +++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/t/README b/t/README
index 7f409392537..c2f996656d3 100644
--- a/t/README
+++ b/t/README
@@ -371,6 +371,12 @@ declared themselves as leak-free by setting
 "TEST_PASSES_SANITIZE_LEAK=true" before sourcing "test-lib.sh". This
 test mode is used by the "linux-leaks" CI target.
 
+GIT_TEST_SANITIZE_LEAK_LOG=true will log memory leaks to
+"test-results/$TEST_NAME.leak/trace.*" files. Useful in combination
+with "GIT_TEST_PASSING_SANITIZE_LEAK" to check if we're falsely
+reporting a test as "passing" with SANITIZE=leak due to ignored exit
+codes.
+
 GIT_TEST_PROTOCOL_VERSION=<n>, when set, makes 'protocol.version'
 default to n.
 
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 7f730b0f94f..73600c4d887 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -305,6 +305,10 @@ TEST_NUMBER="${TEST_NAME%%-*}"
 TEST_NUMBER="${TEST_NUMBER#t}"
 TEST_RESULTS_DIR="$TEST_OUTPUT_DIRECTORY/test-results"
 TEST_RESULTS_BASE="$TEST_RESULTS_DIR/$TEST_NAME$TEST_STRESS_JOB_SFX"
+TEST_RESULTS_SAN_FILE_PFX=trace
+TEST_RESULTS_SAN_DIR_SFX=leak
+TEST_RESULTS_SAN_FILE=
+TEST_RESULTS_SAN_DIR="$TEST_RESULTS_DIR/$TEST_NAME.$TEST_RESULTS_SAN_DIR_SFX"
 TRASH_DIRECTORY="trash directory.$TEST_NAME$TEST_STRESS_JOB_SFX"
 test -n "$root" && TRASH_DIRECTORY="$root/$TRASH_DIRECTORY"
 case "$TRASH_DIRECTORY" in
@@ -1455,6 +1459,23 @@ then
 			test_done
 		fi
 	fi
+
+	if test_bool_env GIT_TEST_SANITIZE_LEAK_LOG false
+	then
+		if ! mkdir -p "$TEST_RESULTS_SAN_DIR"
+		then
+			BAIL_OUT "cannot create $TEST_RESULTS_SAN_DIR"
+		fi &&
+		TEST_RESULTS_SAN_FILE="$TEST_RESULTS_SAN_DIR/$TEST_RESULTS_SAN_FILE_PFX"
+
+		# Don't litter *.leak dirs if there was nothing to report
+		test_atexit "rmdir \"$TEST_RESULTS_SAN_DIR\" 2>/dev/null || :"
+
+		prepend_var LSAN_OPTIONS : dedup_token_length=9999
+		prepend_var LSAN_OPTIONS : log_exe_name=1
+		prepend_var LSAN_OPTIONS : log_path=\"$TEST_RESULTS_SAN_FILE\"
+		export LSAN_OPTIONS
+	fi
 elif test_bool_env GIT_TEST_PASSING_SANITIZE_LEAK false
 then
 	BAIL_OUT "GIT_TEST_PASSING_SANITIZE_LEAK=true has no effect except when compiled with SANITIZE=leak"
-- 
2.37.1.1062.g385eac7fccf