merge-ort: fix small memory leak in detect_and_process_renames()

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, just remove the
if-check; free() knows to skip NULL pointers.  This change 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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/merge-ort.c b/merge-ort.c
index d85b1cd99e9a4c9527cca8ef684d4b8aed0f6a07..3d7f9feb6f755a09fd0b85257402c4ac01c96c00 100644 (file)
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -3086,12 +3086,11 @@ static int detect_and_process_renames(struct merge_options *opt,
                                      struct tree *side1,
                                      struct tree *side2)
 {
-       struct diff_queue_struct combined;
+       struct diff_queue_struct combined = { 0 };
        struct rename_info *renames = &opt->priv->renames;
-       int need_dir_renames, s, clean = 1;
+       int need_dir_renames, s, i, clean = 1;
        unsigned detection_run = 0;
 
-       memset(&combined, 0, sizeof(combined));
        if (!possible_renames(renames))
                goto cleanup;
 
@@ -3175,13 +3174,9 @@ simple_cleanup:
                free(renames->pairs[s].queue);
                DIFF_QUEUE_CLEAR(&renames->pairs[s]);
        }
-       if (combined.nr) {
-               int i;
-               for (i = 0; i < combined.nr; i++)
-                       pool_diff_free_filepair(&opt->priv->pool,
-                                               combined.queue[i]);
-               free(combined.queue);
-       }
+       for (i = 0; i < combined.nr; i++)
+               pool_diff_free_filepair(&opt->priv->pool, combined.queue[i]);
+       free(combined.queue);
 
        return clean;
 }