GH-141212: Fix possible memory leak in gc_mark_span_push (gh-141213)

sergey-miryanov · web-flow · commit f835552946e2 · 2025-11-10T11:19:13.000-05:00
diff --git a/Python/gc_free_threading.c b/Python/gc_free_threading.c
@@ -675,10 +675,11 @@ gc_mark_span_push(gc_span_stack_t *ss, PyObject **start, PyObject **end)
         else {
             ss->capacity *= 2;
         }
-        ss->stack = (gc_span_t *)PyMem_Realloc(ss->stack, ss->capacity * sizeof(gc_span_t));
-        if (ss->stack == NULL) {
+        gc_span_t *new_stack = (gc_span_t *)PyMem_Realloc(ss->stack, ss->capacity * sizeof(gc_span_t));
+        if (new_stack == NULL) {
             return -1;
         }
+        ss->stack = new_stack;
     }
     assert(end > start);
     ss->stack[ss->size].start = start;

Original file line number	Diff line number	Diff line change
`@@ -675,10 +675,11 @@ gc_mark_span_push(gc_span_stack_t ss, PyObject start, PyObject *end)`
`675`	`675`	`else {`
`676`	`676`	`ss->capacity *= 2;`
`677`	`677`	`}`
`678`		`- ss->stack = (gc_span_t )PyMem_Realloc(ss->stack, ss->capacity sizeof(gc_span_t));`
`679`		`- if (ss->stack == NULL) {`
	`678`	`+ gc_span_t new_stack = (gc_span_t )PyMem_Realloc(ss->stack, ss->capacity * sizeof(gc_span_t));`
	`679`	`+ if (new_stack == NULL) {`
`680`	`680`	`return -1;`
`681`	`681`	`}`
	`682`	`+ ss->stack = new_stack;`
`682`	`683`	`}`
`683`	`684`	`assert(end > start);`
`684`	`685`	`ss->stack[ss->size].start = start;`