c - 即使使用 -g 选项，GCC 也不会生成行号信息

Question

我已经从源代码构建并安装了 GCC 4.8.1:

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-unknown-linux-gnu/4.8.1/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ./configure --disable-multilib
Thread model: posix
gcc version 4.8.1 (GCC) 

我写了一个简单的无用程序:

$ cat hw.c
#include <stdio.h>

void foo()
{
    int a;
    scanf("%d", &a); /* So I can press ctrl+c here. */
    printf("Hello world!\n");
}

int main()
{
    foo();   
}

现在我编译这个:

$ gcc -g -O0 hw.c -o hw

然后开始用GDB调试:

$ gdb hw
GNU gdb (Ubuntu/Linaro 7.4-2012.04-0ubuntu2.1) 7.4-2012.04
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.launchpad.net/gdb-linaro/>...
Reading symbols from /home/calmarius/workdir/crucible/hw/hw...done.
(gdb) 

运行它并立即按 Ctrl+C:

(gdb) run
Starting program: /home/dcsirmaz/workdir/crucible/hw/hw 
^C
Program received signal SIGINT, Interrupt.
0x00007ffff7b018b0 in __read_nocancel () at ../sysdeps/unix/syscall-template.S:82
82  ../sysdeps/unix/syscall-template.S: Nincs ilyen fájl vagy könyvtár.

我在回溯中得到了函数名，但我的代码中没有行号:

(gdb) bt
#0  0x00007ffff7b018b0 in __read_nocancel () at ../sysdeps/unix/syscall-template.S:82
#1  0x00007ffff7a95ff8 in _IO_new_file_underflow (fp=0x7ffff7dd4340) at fileops.c:619
#2  0x00007ffff7a9703e in _IO_default_uflow (fp=0x7ffff7dd4340) at genops.c:440
#3  0x00007ffff7a74fb6 in _IO_vfscanf_internal (s=<optimized out>, format=<optimized out>, argptr=0x7fffffffe018, errp=0x0) at vfscanf.c:620
#4  0x00007ffff7a790bd in __isoc99_scanf (format=<optimized out>) at isoc99_scanf.c:37
#5  0x000000000040054e in foo ()
#6  0x0000000000400568 in main ()

出了什么问题？也许是配置问题？

Answer 1

你的 gdb 太旧了——你需要更新的 gdb(我用的是 7.6)来理解 gcc 4.8.1 生成的调试信息