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#include "stddef.h" // for NULL
#include <errno.h> // for errno, EINVAL, ENOMEM
#include <stdint.h> // for uintptr_t
#include <stdlib.h> // for size_t, aligned_alloc, malloc
void *aligned_alloc(size_t alignment, size_t size)
{
if (alignment == 0 || (alignment & (alignment - 1)) != 0) {
errno = EINVAL;
return NULL;
}
if (size % alignment != 0) {
errno = EINVAL;
return NULL;
}
if (size == 0) {
return NULL;
}
size_t total_size = size + alignment - 1 + sizeof(void *);
void *raw_ptr = malloc(total_size);
if (raw_ptr == NULL) {
errno = ENOMEM;
return NULL;
}
uintptr_t raw_addr = (uintptr_t)raw_ptr;
uintptr_t aligned_addr = (raw_addr + sizeof(void *) + alignment - 1) &
~(alignment - 1);
void **orig_ptr_slot = (void **)(aligned_addr - sizeof(void *));
*orig_ptr_slot = raw_ptr;
return (void *)aligned_addr;
}
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