一个可变参函数

   今天老师讲到了可变形参,就man了下va_arg,看着郁闷,都是宏...照着va_arg的大体,自己写了个玩玩,第一个参数稍微做点修改,应该可以处理更多类型参数.

下面贴下代码:

#include <stdio.h>

void m_printf(int,...);

int main(char argc,char **argv){
    m_printf(3,3323,23323,3453453);
    return 0;
}

void m_printf(int i,...){
    int c=0;
    __asm__ __volatile__("pushl %%esi;"::);
    while(i){
        int eax;
           __asm__ __volatile__("movl -12(%%ebp),%%esi;movl 12(%%ebp,%%esi),%0;"
                          :"=r"(eax)
                         :);
        printf("%d\n",eax);
        c+=4;
        i--;
    }
    __asm__ __volatile__("popl %%esi;"::);
}

顺便也贴下她的汇编:

.file "01.c"

.text

.globl main

.type main, @function

main:

pushl %ebp

movl %esp, %ebp

andl $-16, %esp

subl $32, %esp

movl 8(%ebp), %eax

movb %al, 28(%esp)

movl $3453453, 12(%esp)

movl $23323, 8(%esp)

movl $7885558, 4(%esp)

movl $3, (%esp)

call m_printf

movl $0, %eax

leave

ret

.size main, .-main

.section .rodata

.LC0:

.string "%d\n"

.text

.globl m_printf

.type m_printf, @function

m_printf:

pushl %ebp

movl %esp, %ebp

subl $40, %esp

movl $0, -12(%ebp)

#APP

# 12 "01.c" 1

pushl %esi;

# 0 "" 2

#NO_APP

jmp .L4

.L5:

#APP

# 15 "01.c" 1

movl -12(%ebp),%esi;movl 12(%ebp,%esi),%eax;

# 0 "" 2

#NO_APP

movl %eax, -16(%ebp)

movl $.LC0, %eax

movl -16(%ebp), %edx

movl %edx, 4(%esp)

movl %eax, (%esp)

call printf

addl $4, -12(%ebp)

subl $1, 8(%ebp)

.L4:

cmpl $0, 8(%ebp)

jne .L5

#APP

# 22 "01.c" 1

popl %esi;

# 0 "" 2

#NO_APP

leave

ret

.size m_printf, .-m_printf

.ident "GCC: (Ubuntu 4.4.3-4ubuntu5) 4.4.3"

.section .note.GNU-stack,"",@progbits