From owner-freebsd-hackers  Wed Dec 13 13:30:28 2000
From owner-freebsd-hackers@FreeBSD.ORG  Wed Dec 13 13:30:25 2000
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from Gloria.CAM.ORG (Gloria.CAM.ORG [205.151.116.34])
	by hub.freebsd.org (Postfix) with ESMTP id 2C68F37B699
	for <freebsd-hackers@freebsd.org>; Wed, 13 Dec 2000 13:30:20 -0800 (PST)
Received: from localhost (intmktg@localhost)
	by Gloria.CAM.ORG (8.9.3/8.9.3) with ESMTP id QAA12440
	for <freebsd-hackers@freebsd.org>; Wed, 13 Dec 2000 16:25:46 -0500
Date: Wed, 13 Dec 2000 16:25:46 -0500 (EST)
From: Marc Tardif <intmktg@CAM.ORG>
To: freebsd-hackers@freebsd.org
Subject: syscall assembly
Message-ID: <Pine.LNX.4.10.10012131620390.12420-100000@Gloria.CAM.ORG>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: owner-freebsd-hackers@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

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)



To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message