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Properly handle fencepost with MALLOC_ALIGN_MASK

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This commit is contained in:
H.J. Lu
2012-09-24 08:58:04 -07:00
parent a9f8e53a5b
commit ced6f16ee9
3 changed files with 14 additions and 4 deletions
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10
malloc/arena.c
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@@ -655,15 +655,19 @@ heap_trim(heap_info *heap, size_t pad)
unsigned long pagesz = GLRO(dl_pagesize);
mchunkptr top_chunk = top(ar_ptr), p, bck, fwd;
heap_info *prev_heap;
long new_size, top_size, extra;
long new_size, top_size, extra, prev_size, misalign;
/* Can this heap go away completely? */
while(top_chunk == chunk_at_offset(heap, sizeof(*heap))) {
prev_heap = heap->prev;
p = chunk_at_offset(prev_heap, prev_heap->size - (MINSIZE-2*SIZE_SZ));
prev_size = prev_heap->size - (MINSIZE-2*SIZE_SZ);
p = chunk_at_offset(prev_heap, prev_size);
/* fencepost must be properly aligned. */
misalign = ((long) p) & MALLOC_ALIGN_MASK;
p = chunk_at_offset(prev_heap, prev_size - misalign);
assert(p->size == (0|PREV_INUSE)); /* must be fencepost */
p = prev_chunk(p);
new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ);
new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ) + misalign;
assert(new_size>0 && new_size<(long)(2*MINSIZE));
if(!prev_inuse(p))
new_size += p->prev_size;