...
| Code Block | ||
|---|---|---|
| ||
size_t resize = 1024; size_t alignment = 1 << 12; int *ptr; int *ptr1; if ((ptr = aligned_alloc(alignment , sizeof(int))) == NULL) { /* handle error */ } /* ... */ if ((ptr1 = realloc(ptr, resize)) == NULL) { /* handle error */ } |
...
| Code Block |
|---|
#include <stdlib.h>
#include <stdio.h>
int main(void) {
size_t size = 16;
size_t resize = 1024;
size_t align = 1 << 12;
int *ptr;
int *ptr1;
if (posix_memalign((void **)&ptr, align , size) != 0) {
exit(EXIT_FAILURE);
}
printf("memory aligned to %d bytes\n", align);
printf("ptr = %p\n\n", ptr);
if ((ptr1 = realloc((int *)ptr, resize)) == NULL) {
exit(EXIT_FAILURE);
}
printf puts("After realloc(): \n");
printf("ptr1 = %p\n", ptr1);
free(ptr1);
return 0;
}
|
produces the following (unexpected) output.:
| Code Block |
|---|
memory aligned to 4096 bytes
ptr = 0x1621b000
After realloc():
ptr1 = 0x1621a010
|
Unfortunately, ptr1 is no longer aligned to 4096 bytes.
Compliant Solution
This compliant solution implements an aligned realloc() function. It allocates new memory of resize bytes with an alignment equal to that of old memory and copies old memory into it. It then frees the old memory.
| Code Block | ||
|---|---|---|
| ||
size_t resize = 1024; size_t alignment = 1 << 12; size_t newsize; int *ptr; int *ptr1; if ((ptr = aligned_alloc(alignment , sizeof(int))) == NULL) { /* handle error */ } /* ... */ if ((ptr1 = aligned_alloc(alignment , resize)) == NULL) { /* handle error */ } newsize = MIN(size, resize); if((memcpy(ptr1, ptr, newsizesizeof(int)) == NULL) { /* handle error */ } free(ptr); |
...