Question

In the code below I am getting an EXC_BAD_ACCESS error for no apparent reason when I call print vertex. The pointers point to the exact same location, but somehow it crashes when I pass in vp2.

#include <stdio.h>

typedef struct {
    float x;
    float y;
    float z;
} Vertex;

void printVertex(Vertex *v);

int main (int argc, const char * argv[])
{
    Vertex v = {1,0,2};
    int memL = (int)&v;
    Vertex *vp = &v;

    printf("Memory Location: %i\n", memL);
    printf("Memory Pointed to by Pointer: %i\n", (int)vp);

    Vertex *vp2 = (Vertex *)memL;
    printf("Memory Pointed to by Pointer from memory location: %i\n", (int)vp2);

    printVertex(vp);  // Executes normally
    printVertex(vp2); // EXC_BAD_ACCESS

    return 0;
}

void printVertex(Vertex *v)
{
    printf("Vertex[%f,%f,%f]\n", v->x, v->y, v->z); // EXC_BAD_ACCESS when vp2 passed in
}

Output:

Memory Location: 1606416816
Memory Pointed to by Pointer: 1606416816
Memory Pointed to by Pointer from memory location: 1606416816
Vertex[1.000000,0.000000,2.000000]
EXC_BAD_ACCESS Error

Answer 1

int memL = (int)&v;

Might be truncating the adddress of v. You could try:

intptr_t memL = (intptr_t)&v;

to see if this is the case. This should not crash if truncation is a problem.