Description:
Many platforms have requirements that certain types must be aligned
to certain address boundaries, such as ints needing to be on 4-byte
boundaries. Attempting to access variables with incorrect
alignment may cause performance loss or even program failure (eg. a
bus signal).
There are times which it's useful to be able to programatically
access these requirements, such as for dynamic allocators.
|
Example: #include <stdio.h>
#include <stdlib.h>
#include <ccan/alignof/alignof.h>
// Output contains "ALIGNOF(char) == 1"
// Will also print out whether an onstack char array can hold a long.
int main(int argc, char *argv[])
{
char arr[sizeof(int)];
printf("ALIGNOF(char) == %zu\n", ALIGNOF(char));
if ((unsigned long)arr % ALIGNOF(int)) {
printf("arr %p CANNOT hold an int\n", arr);
exit(1);
} else {
printf("arr %p CAN hold an int\n", arr);
exit(0);
}
}
|
