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Explicitly check for GCC's atomic functions instead of depending on the __GNUC__ define.

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Add a comment mentioning the limitation even though the _ref_count value is hanled atomically.
This commit is contained in:
Eric Haszlakiewicz
2017-09-02 14:48:17 -04:00
parent ab0d4dbc69
commit 5b11e9adff
2 changed files with 32 additions and 2 deletions
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10
json_object.c
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@@ -165,7 +165,7 @@ extern struct json_object* json_object_get(struct json_object *jso)
{
if (!jso) return jso;
#if defined __GNUC__
#ifdef HAVE_ATOMIC_BUILTINS
__sync_add_and_fetch(&jso->_ref_count, 1);
#else
++jso->_ref_count;
@@ -178,7 +178,13 @@ int json_object_put(struct json_object *jso)
{
if(!jso) return 0;
#if defined __GNUC__
#ifdef HAVE_ATOMIC_BUILTINS
/* Note: this only allow the refcount to remain correct
* when multiple threads are adjusting it. It is still an error
* for a thread to decrement the refcount if it doesn't "own" it,
* as that can result in the thread that loses the race to 0
* operating on an already-freed object.
*/
if (__sync_sub_and_fetch(&jso->_ref_count, 1) > 0) return 0;
#else
if (--jso->_ref_count > 0) return 0;