syscall assembly

[Marc Tardif]

Considering the following C code:

#include <fcntl.h>
int main() {
  open("file", O_RDONLY);
  return 0;
}

compiled with gcc -S -O2, the following
assembly code is generated:

main:
        pushl %ebp
        movl %esp,%ebp
        subl $8,%esp
        addl $-8,%esp
        pushl $0
        pushl $.LC0
        call open
        xorl %eax,%eax
        leave
     
What is the purpose of the subl and addl
instructions? On Linux, they are simply
unexistent..

Notes:
FreeBSD fbsd.b0x.com 4.2-RELEASE
gcc version 2.95.2 19991024 (release)



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