prompt> more main.c
#include <stdio.h>

int main ( void )
{
   int a = 5;
   int b = 3;
   int c = sum(a,b);
   printf("%d + %d = %d\n",a,b,c);
   
   return 0;
}

prompt> more sub.c
int sum (int x, int y)
{
   int t = x + y;
   return t;
}

prompt> gcc -g -m32 -O0 main.c sub.c


0804841d <main>:
 804841d:	55                   	push   %ebp
 804841e:	89 e5                	mov    %esp,%ebp
 8048420:	83 e4 f0             	and    $0xfffffff0,%esp
 8048423:	83 ec 20             	sub    $0x20,%esp
 8048426:	c7 44 24 14 05 00 00 	movl   $0x5,0x14(%esp)
 804842d:	00 
 804842e:	c7 44 24 18 03 00 00 	movl   $0x3,0x18(%esp)
 8048435:	00 
 8048436:	8b 44 24 18          	mov    0x18(%esp),%eax
 804843a:	89 44 24 04          	mov    %eax,0x4(%esp)
 804843e:	8b 44 24 14          	mov    0x14(%esp),%eax
 8048442:	89 04 24             	mov    %eax,(%esp)
 8048445:	e8 2f 00 00 00       	call   8048479 <sum>
 804844a:	89 44 24 1c          	mov    %eax,0x1c(%esp)
 804844e:	8b 44 24 1c          	mov    0x1c(%esp),%eax
 8048452:	89 44 24 0c          	mov    %eax,0xc(%esp)
 8048456:	8b 44 24 18          	mov    0x18(%esp),%eax
 804845a:	89 44 24 08          	mov    %eax,0x8(%esp)
 804845e:	8b 44 24 14          	mov    0x14(%esp),%eax
 8048462:	89 44 24 04          	mov    %eax,0x4(%esp)
 8048466:	c7 04 24 20 85 04 08 	movl   $0x8048520,(%esp)
 804846d:	e8 7e fe ff ff       	call   80482f0 <printf@plt>
 8048472:	b8 00 00 00 00       	mov    $0x0,%eax
 8048477:	c9                   	leave  
 8048478:	c3                   	ret    




08048479 <sum>:
 8048479:	55                   	push   %ebp
 804847a:	89 e5                	mov    %esp,%ebp
 804847c:	83 ec 10             	sub    $0x10,%esp
 804847f:	8b 45 0c             	mov    0xc(%ebp),%eax
 8048482:	8b 55 08             	mov    0x8(%ebp),%edx
 8048485:	01 d0                	add    %edx,%eax
 8048487:	89 45 fc             	mov    %eax,-0x4(%ebp)
 804848a:	8b 45 fc             	mov    -0x4(%ebp),%eax
 804848d:	c9                   	leave  
 804848e:	c3                   	ret    
 804848f:	90                   	nop