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

The previous code had two bugs. First, the debug offset in the mimalloc
heap includes the two pymalloc debug words, but the pointer passed to
fill_mem_debug does not include them. Second, the current object heap is
correct source for allocations, but not deallocations.
This commit is contained in:
Sam Gross 2024-02-28 15:50:09 -05:00 committed by GitHub
parent df5212df6c
commit 75c6c05fea
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GPG Key ID: B5690EEEBB952194
1 changed files with 13 additions and 4 deletions
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17
Objects/obmalloc.c
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@ -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);
}
@ -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) */
@ -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);
}