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fix for realloc with size 0: returning NULL from realloc now always indicates an error (issue #574)

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This commit is contained in:
Daan Leijen 2022-04-19 10:31:55 -07:00
parent 8713959498
commit a158aef235
2 changed files with 11 additions and 2 deletions
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7
src/alloc.c
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@ -632,8 +632,11 @@ void* mi_expand(void* p, size_t newsize) mi_attr_noexcept {
}
void* _mi_heap_realloc_zero(mi_heap_t* heap, void* p, size_t newsize, bool zero) mi_attr_noexcept {
const size_t size = _mi_usable_size(p,"mi_realloc"); // also works if p == NULL
if (mi_unlikely(newsize <= size && newsize >= (size / 2))) {
// if p == NULL then behave as malloc.
// else if size == 0 then reallocate to a zero-sized block (and don't return NULL, just as mi_malloc(0)).
// (this means that returning NULL always indicates an error, and `p` will not have been freed in that case.)
const size_t size = _mi_usable_size(p,"mi_realloc"); // also works if p == NULL (with size 0)
if (mi_unlikely(newsize <= size && newsize >= (size / 2) && newsize > 0)) { // note: newsize must be > 0 or otherwise we return NULL for realloc(NULL,0)
// todo: adjust potential padding to reflect the new size?
return p; // reallocation still fits and not more than 50% waste
}

6
test/test-api.c
View File

@ -198,6 +198,12 @@ int main(void) {
mi_free(q);
};
CHECK_BODY("reallocarray-null-sizezero") {
void* p = mi_reallocarray(NULL,0,16); // issue #574
result = (p != NULL && errno == 0);
mi_free(p);
};
// ---------------------------------------------------
// Heaps
// ---------------------------------------------------