[3.6] bpo-31626: Fixed a bug in debug memory allocator. (GH-3844) by miss-islington · Pull Request #4191 · python/cpython

Expand Up @@ -1914,7 +1914,7 @@ static void * _PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes) { debug_alloc_api_t *api = (debug_alloc_api_t *)ctx; uint8_t *q = (uint8_t *)p, *oldq; uint8_t *q = (uint8_t *)p; uint8_t *tail; size_t total; /* nbytes + 4*SST */ size_t original_nbytes; Expand All @@ -1931,20 +1931,11 @@ _PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes) /* overflow: can't represent total as a Py_ssize_t */ return NULL;
/* Resize and add decorations. We may get a new pointer here, in which * case we didn't get the chance to mark the old memory with DEADBYTE, * but we live with that. */ oldq = q; /* Resize and add decorations. */ q = (uint8_t *)api->alloc.realloc(api->alloc.ctx, q - 2*SST, total); if (q == NULL) return NULL;
if (q == oldq && nbytes < original_nbytes) { /* shrinking: mark old extra memory dead */ memset(q + nbytes, DEADBYTE, original_nbytes - nbytes); }
write_size_t(q, nbytes); assert(q[SST] == (uint8_t)api->api_id); for (i = 1; i < SST; ++i) Expand Down