无论我使用的是printf还是puts,为什么在拆卸时都显示puts? [英] Why it shows puts when I disassemble no matter whether I'm using printf or puts?
问题描述
我对编程还很陌生,想问为什么我用不同的代码会得到相同的结果.我实际上是在读一本书,而本书中的示例是使用printf的(同样在Assembler中).在这种情况下,它说< printf @ plt>
.本书中的汇编代码与我的不同,但C代码相同.我的处理器只是在计算不同吗?
I'm pretty new to programming and wanted to ask why I get the same result with different code. I'm actually reading a book and the example in the book is with printf (also in Assembler). In this case it says <printf@plt>
. The assembler code in the book differs from mine but C Code is the same. Is my processor just computing different?
(问题在通话中< + 34>
< puts @ plt>
)
代码1:
#include <stdio.h>
int main()
{
int i;
for(i=0; i<10; i++)
{
printf("Hello, world!\n");
}
return 0;
}
代码2:
#include <stdio.h>
int main()
{
int i;
for(i=0; i<10; i++)
{
puts("Hello, world!\n");
}
return 0;
}
反汇编的代码1:
Dump of assembler code for function main:
0x080483eb <+0>: lea ecx,[esp+0x4]
0x080483ef <+4>: and esp,0xfffffff0
0x080483f2 <+7>: push DWORD PTR [ecx-0x4]
0x080483f5 <+10>: push ebp
0x080483f6 <+11>: mov ebp,esp
0x080483f8 <+13>: push ecx
=> 0x080483f9 <+14>: sub esp,0x14
0x080483fc <+17>: mov DWORD PTR [ebp-0xc],0x0
0x08048403 <+24>: jmp 0x8048419 <main+46>
0x08048405 <+26>: sub esp,0xc
0x08048408 <+29>: push 0x80484b0
0x0804840d <+34>: call 0x80482c0 <puts@plt>
0x08048412 <+39>: add esp,0x10
0x08048415 <+42>: add DWORD PTR [ebp-0xc],0x1
0x08048419 <+46>: cmp DWORD PTR [ebp-0xc],0x9
0x0804841d <+50>: jle 0x8048405 <main+26>
0x0804841f <+52>: mov eax,0x0
0x08048424 <+57>: mov ecx,DWORD PTR [ebp-0x4]
0x08048427 <+60>: leave
0x08048428 <+61>: lea esp,[ecx-0x4]
0x0804842b <+64>: ret
End of assembler dump.
反汇编代码2:
Dump of assembler code for function main:
0x080483eb <+0>: lea ecx,[esp+0x4]
0x080483ef <+4>: and esp,0xfffffff0
0x080483f2 <+7>: push DWORD PTR [ecx-0x4]
0x080483f5 <+10>: push ebp
0x080483f6 <+11>: mov ebp,esp
0x080483f8 <+13>: push ecx
0x080483f9 <+14>: sub esp,0x14
0x080483fc <+17>: mov DWORD PTR [ebp-0xc],0x0
0x08048403 <+24>: jmp 0x8048419 <main+46>
=> 0x08048405 <+26>: sub esp,0xc
0x08048408 <+29>: push 0x80484b0
0x0804840d <+34>: call 0x80482c0 <puts@plt>
0x08048412 <+39>: add esp,0x10
0x08048415 <+42>: add DWORD PTR [ebp-0xc],0x1
0x08048419 <+46>: cmp DWORD PTR [ebp-0xc],0x9
0x0804841d <+50>: jle 0x8048405 <main+26>
0x0804841f <+52>: mov eax,0x0
0x08048424 <+57>: mov ecx,DWORD PTR [ebp-0x4]
0x08048427 <+60>: leave
0x08048428 <+61>: lea esp,[ecx-0x4]
0x0804842b <+64>: ret
End of assembler dump.
推荐答案
首选 puts
函数,因为它在功能(无格式字符串解码)和参数传递方面都比较简单.
The puts
function is preferred because it is simpler to in both functionality (no format string decoding) and argument passing.
例如,System V ABI x86调用约定要求在 RAX
中设置XMM(YMM)参数的数量( printf
是可变的). puts
更容易,因为只有单个参数与 RDI
一起传递.
For instance, System V ABI x86 calling conventions require to set number of XMM (YMM) arguments (printf
is variadic) in RAX
. puts
is easier, as there is only single argument passed with RDI
.
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