Calling C functions with parameter lists, does not play well with structs or doubles.

call_varg.c

#include <stdlib.h>
#include <string.h>
#include <stdio.h>


void *__call_varg_impl(void *f, int n_args, void **argv)
{
		unsigned int param[n_args];
		int ret;
		memcpy(param, argv, n_args * sizeof(void*));
		asm volatile ("movl %0, %%esp;" : : "r" (param));
		asm volatile ("call %0;" : : "r" (f));
		asm volatile ("movl %%eax, %0;" : "=r" (ret));
		return ret;
}

struct __test_struct {
		int a;
		int b;
		int c;
};

int testfunc(int a, int b, struct __test_struct *_st0, struct __test_struct *_st1)
{
		return a + b + _st0->a + _st0->b + _st0->c + 
				_st1->a + _st1->b + _st1->c;
}

int main(int argc, char *argv[])
{
		struct __test_struct st0 = {1,2,3}, st1 = {4,5,6};
		void **arglst[] = {
				10, 20, &st0, &st1
		};
		int res = (int) __call_varg_impl(testfunc, sizeof(arglst), arglst);
		printf("%d\n", res);
		return 0;
}