fprintf注意的问题-凯发app官方网站

#include <stdio.h> #include <stdarg.h> static char msg[1024]; static int my_print1(file *fp, const char *fmt, ...) { return (fprintf(fp, fmt)); } static int my_print2(file *fp, const char *fmt, ...) { int t; va_list body; va_start(body, fmt); t = vsnprintf(msg, 1024, fmt, body); va_end(body); return (fprintf(fp, msg)); } int main(int argc, char **argv) { my_print1(stderr, "%s int.%d \n", "char print", 3); my_print2(stderr, "%s int.%d \n", "char print", 3); return (0); }

再看看用gcc编译后的汇编代码:

.file "a.c" .text .type my_print1,@function my_print1: pushl %ebp movl %esp, %ebp subl $8, %esp subl $8, %esp pushl 12(%ebp) pushl 8(%ebp) call fprintf addl $16, %esp leave ret .lfe1: .size my_print1,.lfe1-my_print1 .type my_print2,@function my_print2: pushl %ebp movl %esp, %ebp subl $8, %esp leal 16(%ebp), %eax movl %eax, -8(%ebp) pushl -8(%ebp) pushl 12(%ebp) pushl $1024 pushl $msg call vsnprintf addl $16, %esp movl %eax, -4(%ebp) subl $8, %esp pushl $msg pushl 8(%ebp) call fprintf addl $16, %esp leave ret .lfe2: .size my_print2,.lfe2-my_print2 .section .rodata .lc0: .string "char print" .lc1: .string "%s int.%d \n" .text .globl main .type main,@function main: pushl %ebp movl %esp, %ebp subl $8, %esp andl $-16, %esp movl $0, %eax subl %eax, %esp pushl $3 pushl $.lc0 pushl $.lc1 pushl stderr call my_print1 addl $16, %esp pushl $3 pushl $.lc0 pushl $.lc1 pushl stderr call my_print2 addl $16, %esp movl $0, %eax leave ret .lfe3: .size main,.lfe3-main .local msg .comm msg,1024,32 .ident "gcc: (gnu) 3.2.2 20030222 (red hat linux 3.2.2-5)"

看看输出结果:
[gan@gan stack]$ ls
a.c a.out a.s

[gan@gan stack]$ a.out
媫鼖]魦u鴫靅脨怳夊wvs?"???伱y? int.134513410
char print int.3

一个为乱码, 另外一个才是我们想要的结果.

阅读(3106) | 评论(0) | 转发(0) |

上一篇：经典散户心态线路图

下一篇：vi学习2 --- 编辑多个文件

给主人留下些什么吧！~~

| | | | |

感谢所有关心和支持过chinaunix的朋友们