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Don't add to NULL in iterator.

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In C it is undefined to add anything to NULL. Clang recently began
taking advantage of this and can assume that if anything is added or
subtracted from a pointer that the pointer can be assumed non-NULL. The
Address Sanitizer has been updated to report when this happens at
runtime and produces messages like

expat/lib/xmlparse.c:6509:23: runtime error: applying zero offset to null pointer
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior expat/lib/xmlparse.c:6509:23

This can be mitigated with 'p ? p + n : NULL' which optimizes to just
the add in all optimizing compilers, but avoids the undefined behavior.
This commit is contained in:
Ben Wagner 2020-04-07 13:12:18 -04:00
parent c0bfb97ddd
commit 49c165c5a8
1 changed files with 1 additions and 1 deletions
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2
expat/lib/xmlparse.c
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@ -6506,7 +6506,7 @@ hashTableInit(HASH_TABLE *p, const XML_Memory_Handling_Suite *ms) {
static void FASTCALL
hashTableIterInit(HASH_TABLE_ITER *iter, const HASH_TABLE *table) {
iter->p = table->v;
iter->end = iter->p + table->size;
iter->end = iter->p ? iter->p + table->size : NULL;
}
static NAMED *FASTCALL