Question

我正在使用

    p12user@ubuntu:~$ uname -a
    Linux ubuntu 2.6.32-40-generic #87-Ubuntu SMP Tue Mar 6 00:56:56 UTC 2012 x86_64 GNU/Linux

    p12user@ubuntu:~$ gdb -v
    GNU gdb (GDB) 7.1-ubuntu
    Copyright (C) 2010 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://www.gnu.org/software/gdb/bugs/>.

    p12user@ubuntu:~/programming$ gcc --version
    gcc (Ubuntu 4.4.3-4ubuntu5.1) 4.4.3
    Copyright (C) 2009 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions.  There is NO
    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

在gdb中调试此程序时，编译为gcc -g program.c：

#include <stdio.h>
int main()
{
   int condition1 = 1;
   if(condition1)
   {
      if(!condition1)
      {
         printf("The control shouldn't come here.\n");
      }
   }
   else
   {
      printf("in else\n");
   }
   return 0;
}

行为是：

Breakpoint 1, main () at program.c:4
4               int condition1 = 1;
(gdb) n
5               if(condition1)
(gdb) n
7                       if(!condition1)
(gdb) n
9                               printf("The control shouldn't come here.\n");
(gdb) n
16              return 0;
(gdb) n
17      }
(gdb)

第9行中的行为在gdb中是意外的。但是，print语句仅在gdb中显示但未执行。如果我将匹配的ELSE（带有一些print语句）与内部IF放在一起，那么这种情况就不会发生，如果外部IF的匹配ELSE被删除，那么这不会发生。我在这里错过了一些小事吗？

Answer 1

确保你正在构建程序而不用任何类型的优化，因为你所展示的程序似乎很容易被优化，这可能导致源代码语句无法进入可执行文件。 / p>

在GCC中你会使用：

gcc -O0 ...

或

g++ -O0 ...

为此。

Answer 2

in

2.6.18-164.el5 #1 SMP Tue Aug 18 15:51:48 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux
gcc version 4.1.2 20080704 (Red Hat 4.1.2-46)
GNU gdb Fedora (6.8-37.el5)

没关系！

gdb意外行为：嵌套if

2 个答案: