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gh-115891: Fix debug byte filling in free-threaded build #116018

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Merged
merged 1 commit into from
Feb 28, 2024
Merged

gh-115891: Fix debug byte filling in free-threaded build #116018

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17 changes: 13 additions & 4 deletions Objects/obmalloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2460,14 +2460,23 @@ write_size_t(void *p, size_t n)
}

static void
fill_mem_debug(debug_alloc_api_t *api, void *data, int c, size_t nbytes)
fill_mem_debug(debug_alloc_api_t *api, void *data, int c, size_t nbytes,
bool is_alloc)
{
#ifdef Py_GIL_DISABLED
if (api->api_id == 'o') {
// Don't overwrite the first few bytes of a PyObject allocation in the
// free-threaded build
_PyThreadStateImpl *tstate = (_PyThreadStateImpl *)_PyThreadState_GET();
size_t debug_offset = tstate->mimalloc.current_object_heap->debug_offset;
size_t debug_offset;
if (is_alloc) {
debug_offset = tstate->mimalloc.current_object_heap->debug_offset;
}
else {
char *alloc = (char *)data - 2*SST; // start of the allocation
debug_offset = _mi_ptr_page(alloc)->debug_offset;
}
debug_offset -= 2*SST; // account for pymalloc extra bytes
if (debug_offset < nbytes) {
memset((char *)data + debug_offset, c, nbytes - debug_offset);
}
Expand Down Expand Up @@ -2553,7 +2562,7 @@ _PyMem_DebugRawAlloc(int use_calloc, void *ctx, size_t nbytes)
memset(p + SST + 1, PYMEM_FORBIDDENBYTE, SST-1);

if (nbytes > 0 && !use_calloc) {
fill_mem_debug(api, data, PYMEM_CLEANBYTE, nbytes);
fill_mem_debug(api, data, PYMEM_CLEANBYTE, nbytes, true);
}

/* at tail, write pad (SST bytes) and serialno (SST bytes) */
Expand Down Expand Up @@ -2603,7 +2612,7 @@ _PyMem_DebugRawFree(void *ctx, void *p)
nbytes = read_size_t(q);
nbytes += PYMEM_DEBUG_EXTRA_BYTES - 2*SST;
memset(q, PYMEM_DEADBYTE, 2*SST);
fill_mem_debug(api, p, PYMEM_DEADBYTE, nbytes);
fill_mem_debug(api, p, PYMEM_DEADBYTE, nbytes, false);
api->alloc.free(api->alloc.ctx, q);
}

Expand Down