You cannot use the syntax you have suggested. If you have a C99 compiler, though, you can do this:

int *p;

p = malloc(3 * sizeof p[0]);
memcpy(p, (int []){ 0, 1, 2 }, 3 * sizeof p[0]);

If your compiler does not support C99 compound literals, you need to use a named template to copy from:

static const int p_init[] = { 0, 1, 2 };
int *p;

p = malloc(3 * sizeof p[0]);
memcpy(p, p_init, 3 * sizeof p[0]);

You cannot use the syntax you have suggested. If you have a C99 compiler, though, you can do this:

int *p;

p = malloc(3 * sizeof p[0]);
memcpy(p, (int []){ 0, 1, 2 }, 3 * sizeof p[0]);

If your compiler does not support C99 compound literals, you need to use a named template to copy from:

int *p;

p = malloc(3 * sizeof p[0]);
{
    static const int p_init[] = { 0, 1, 2 };
    memcpy(p, p_init, 3 * sizeof p[0]);
}