GCC - How to realign stack?

Question

I try to build an application which uses pthreads and __m128 SSE type. According to GCC manual, default stack alignment is 16 bytes. In order to use __m128, the requirement is t

Answer 1

Another solution would be, to use a padding function, which first aligns the stack and then calls f. So instead of calling f directly, you call pad, which pads the stack first and then calls foowith an aligned stack.

The code would look like this:

#include 
#include 

#define ALIGNMENT 16

void *f(void *x) {
    __m128 y;
    // other stuff
}

void * pad(void *val) {
    unsigned int x; // to get the current address from the stack
    unsigned char pad[ALIGNMENT - ((unsigned int) &x) % ALIGNMENT];
    return f(val);
}

int main(void){
    pthread_t p;
    pthread_create(&p, NULL, pad, NULL);
}