decorate: add clear_decoration() function

There's not currently any way to free the resources associated with a
decoration struct. As a result, we have several memory leaks which
cannot easily be plugged.

Let's add a "clear" function and make use of it in the example code of
t9004. This removes the only leak from that script, so we can mark it as
passing the leak sanitizer.

Curiously this leak is found only when running SANITIZE=leak with clang,
but not with gcc.  But it is a bog-standard leak: we allocate some
memory in a local variable struct, and then exit main() without
releasing it. I'm not sure why gcc doesn't find it. After this
patch, both compilers report it as leak-free.

Note that the clear function takes a callback to free the individual
entries. That's not needed for our example (which is just decorating
with ints), but will be for real callers.

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

diff --git a/decorate.c b/decorate.c
index a5c43c0c1461761bb808b4d6b833222b181843a6..69aeb142b45e9fee08d61dace73f6dc2bce1c2d0 100644 (file)
--- a/decorate.c
+++ b/decorate.c
@@ -81,3 +81,18 @@ void *lookup_decoration(struct decoration *n, const struct object *obj)
                        j = 0;
        }
 }
+
+void clear_decoration(struct decoration *n, void (*free_cb)(void *))
+{
+       if (free_cb) {
+               unsigned int i;
+               for (i = 0; i < n->size; i++) {
+                       void *d = n->entries[i].decoration;
+                       if (d)
+                               free_cb(d);
+               }
+       }
+
+       FREE_AND_NULL(n->entries);
+       n->size = n->nr = 0;
+}

diff --git a/decorate.h b/decorate.h
index ee43dee1f008882094ca9c85f6b28b86ec88fdf6..cdeb17c9df2eb680d85e73e8ed2f48b52f44569f 100644 (file)
--- a/decorate.h
+++ b/decorate.h
@@ -58,4 +58,14 @@ void *add_decoration(struct decoration *n, const struct object *obj, void *decor
  */
 void *lookup_decoration(struct decoration *n, const struct object *obj);
 
+/*
+ * Clear all decoration entries, releasing any memory used by the structure.
+ * If free_cb is not NULL, it is called for every decoration value currently
+ * stored.
+ *
+ * After clearing, the decoration struct can be used again. The "name" field is
+ * retained.
+ */
+void clear_decoration(struct decoration *n, void (*free_cb)(void *));
+
 #endif

diff --git a/t/helper/test-example-decorate.c b/t/helper/test-example-decorate.c
index 2ed910adaa3da3b5db771679ccb1eefb0a8da2f5..8f59f6be4cff6c53da68ebb4ea7201e71793cbe1 100644 (file)
--- a/t/helper/test-example-decorate.c
+++ b/t/helper/test-example-decorate.c
@@ -72,5 +72,7 @@ int cmd__example_decorate(int argc UNUSED, const char **argv UNUSED)
        if (objects_noticed != 2)
                BUG("should have 2 objects");
 
+       clear_decoration(&n, NULL);
+
        return 0;
 }

diff --git a/t/t9004-example.sh b/t/t9004-example.sh
index 7e8894a4a70648fd12d3ab4425f1beac2c3e4641..590aab0304c679b6559df0e840ddce6dacc684af 100755 (executable)
--- a/t/t9004-example.sh
+++ b/t/t9004-example.sh
@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='check that example code compiles and runs'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'decorate' '