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array: treat git_array ptrs as void *

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Avoid sloppy aliasing in our (re-)allocation, which is undefined
behavior. This has been problematic before and was helped by `volatile`
(see b62a6a13b2) but that is not
technically correct, and some compilers / architectures do not
understand that `ptr` is changing due to its aliasing.

Just make `git_array_alloc` behave like `realloc`, taking a `void *` and
returning a `void *`.
This commit is contained in:
Edward Thomson
2024-04-29 19:16:29 +01:00
parent 5f796f881b
commit 54218b5506
1 changed files with 18 additions and 17 deletions
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35
src/util/array.h
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@@ -41,39 +41,40 @@
#define GIT_ERROR_CHECK_ARRAY(a) GIT_ERROR_CHECK_ALLOC((a).ptr)
typedef git_array_t(char) git_array_generic_t;
/* use a generic array for growth, return 0 on success */
GIT_INLINE(int) git_array_grow(void *_a, size_t item_size)
GIT_INLINE(void *) git_array__alloc(void *arr, size_t *size, size_t *asize, size_t item_size)
{
volatile git_array_generic_t *a = _a;
size_t new_size;
char *new_array;
void *new_array;
if (a->size < 8) {
if (*size < *asize)
return arr;
if (*size < 8) {
new_size = 8;
} else {
if (GIT_MULTIPLY_SIZET_OVERFLOW(&new_size, a->size, 3))
if (GIT_MULTIPLY_SIZET_OVERFLOW(&new_size, *asize, 3))
goto on_oom;
new_size /= 2;
}
if ((new_array = git__reallocarray(a->ptr, new_size, item_size)) == NULL)
if ((new_array = git__reallocarray(arr, new_size, item_size)) == NULL)
goto on_oom;
a->ptr = new_array;
a->asize = new_size;
return 0;
*asize = new_size;
return new_array;
on_oom:
git_array_clear(*a);
return -1;
git__free(arr);
*size = 0;
*asize = 0;
return NULL;
}
#define git_array_alloc(a) \
(((a).size < (a).asize || git_array_grow(&(a), sizeof(*(a).ptr)) == 0) ? \
&(a).ptr[(a).size++] : (void *)NULL)
(((a).size < (a).asize || \
((a).ptr = git_array__alloc((a).ptr, &(a).size, &(a).asize, sizeof(*(a).ptr))) != NULL) ? &(a).ptr[(a).size++] : (void *)NULL)
#define git_array_last(a) ((a).size ? &(a).ptr[(a).size - 1] : (void *)NULL)