[PATCH 1/2] merge-ort: fix small memory leak in detect_and_process_renames()

["Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>]

From: Elijah Newren <newren@gmail.com>

detect_and_process_renames() detects renames on both sides of history
and then combines these into a single diff_queue_struct.  The combined
diff_queue_struct needs to be able to hold the renames found on either
side, and since it knows the (maximum) size it needs, it pre-emptively
grows the array to the appropriate size:

	ALLOC_GROW(combined.queue,
		   renames->pairs[1].nr + renames->pairs[2].nr,
		   combined.alloc);

It then collects the items from each side:

	collect_renames(opt, &combined, MERGE_SIDE1, ...)
	collect_renames(opt, &combined, MERGE_SIDE2, ...)

Note, though, that collect_renames() sometimes determines that some
pairs are unnecessary and does not include them in the combined array.
When it is done, detect_and_process_renames() frees this memory:

	if (combined.nr) {
                ...
		free(combined.queue);
        }

The problem is that sometimes even when there are pairs, none of them are
necessary.  Instead of checking combined.nr, we should check
combined.alloc.  Doing so fixes the following memory leak, as reported
by valgrind:

==PID== 192 bytes in 1 blocks are definitely lost in loss record 107 of 134
==PID==    at 0xADDRESS: malloc
==PID==    by 0xADDRESS: realloc
==PID==    by 0xADDRESS: xrealloc (wrapper.c:126)
==PID==    by 0xADDRESS: detect_and_process_renames (merge-ort.c:3134)
==PID==    by 0xADDRESS: merge_ort_nonrecursive_internal (merge-ort.c:4610)
==PID==    by 0xADDRESS: merge_ort_internal (merge-ort.c:4709)
==PID==    by 0xADDRESS: merge_incore_recursive (merge-ort.c:4760)
==PID==    by 0xADDRESS: merge_ort_recursive (merge-ort-wrappers.c:57)
==PID==    by 0xADDRESS: try_merge_strategy (merge.c:753)
==PID==    by 0xADDRESS: cmd_merge (merge.c:1676)
==PID==    by 0xADDRESS: run_builtin (git.c:461)
==PID==    by 0xADDRESS: handle_builtin (git.c:713)
==PID==    by 0xADDRESS: run_argv (git.c:780)
==PID==    by 0xADDRESS: cmd_main (git.c:911)
==PID==    by 0xADDRESS: main (common-main.c:52)

Reported-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
---
 merge-ort.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/merge-ort.c b/merge-ort.c
index d85b1cd99e9..4f5abc558c5 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -3175,7 +3175,7 @@ simple_cleanup:
 		free(renames->pairs[s].queue);
 		DIFF_QUEUE_CLEAR(&renames->pairs[s]);
 	}
-	if (combined.nr) {
+	if (combined.alloc) {
 		int i;
 		for (i = 0; i < combined.nr; i++)
 			pool_diff_free_filepair(&opt->priv->pool,
-- 
gitgitgadget