__strcpy_sse2_unaligned与-fno-builtin [英] __strcpy_sse2_unaligned with -fno-builtin

问题描述

我正在调试我的程序，然后发生最后一行，我该如何解决它？我使用 -fno-builtin 来查看 strcpy（），但它显示 __ strcpy_sse2_unaligned 正在被调用。

I was debugging my program, then the last line happened, how can I fix it? I used the -fno-builtin to have a look at the strcpy() but it shows that the __strcpy_sse2_unaligned is getting called.

root@19:~/booksrc# gcc -fno-builtin -g char_array2.c
root@19:~/booksrc# gdb -q ./a.out
Reading symbols from ./a.out...done.
(gdb) list
1   #include <stdio.h>
2   #include <string.h>
3   
4   int main() {
5      char str_a[20];
6   
7      strcpy(str_a, "Hello World!\n");
8      printf(str_a);
9   }
(gdb) break 6
Breakpoint 1 at 0x708: file char_array2.c, line 6.
(gdb) break strcpy
Breakpoint 2 at 0x5a0
(gdb) break 8
Breakpoint 3 at 0x71b: file char_array2.c, line 8.
(gdb) run
Starting program: /root/booksrc/a.out 

Breakpoint 1, main () at char_array2.c:7
7      strcpy(str_a, "Hello World!\n");
(gdb) cont
Continuing.

Breakpoint 2, __strcpy_sse2_unaligned ()
    at ../sysdeps/x86_64/multiarch/strcpy-sse2-unaligned.S:47
47  ../sysdeps/x86_64/multiarch/strcpy-sse2-unaligned.S: No such file or directory.

推荐答案

__ strcpy_sse2_unaligned 是在你的机器上使用的 strcpy 的实现。 glibc使用 IFUNC解析器。

__strcpy_sse2_unaligned is the implementation of strcpy which is used on your machine. glibc automatically chooses an optimized implementation based on CPU characteristics, using an IFUNC resolver.

这不需要对GCC和GCC内建程序做任何事情。 GCC发出对 strcpy 的调用。这只是glibc碰巧调用它的函数，它 __ strcpy_sse2_unaligned 。

This does not have to do anything with GCC and GCC built-ins. GCC emits a call to strcpy. It is just that glibc happens to call the function which it __strcpy_sse2_unaligned.

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