使用gdb调用printDebug方法 [英] Use gdb to call a printDebug method

问题描述

我有一个类printDebug方法。它不在代码中的任何地方使用，但我想使用它，当我使用gdb调试（使用调用）。这基本上是以一个格式很好的方式打印对象的内容，例如我可能有一个向量的集合。什么是g ++选项用于此？我尝试了-O0，但是不工作。

I have a class with a printDebug method. Its not used anywhere in the code but I would like to use it when I am debugging with gdb (using call). This is basically to print the contents of the object in a nicely formatted way, for instance I may have a vector of sets. What is the g++ option to use for this? I have tried -O0 but that does not work.

我使用的工作是在构造函数中调试debugPrint并提供一个bool，想打印或什么都不做。这工作正常，但必须有一个更好的方法来做到这一点。

The work around I used was to make a psuedo call in the constructor to debugPrint and provide a bool indicating if you actually want to print or do nothing. This works fine but there has to be a better way to do this.

如果我理解正确，-O0不应该做任何优化，所以死代码不应该被消除，但也许我错了。

If I understand correctly -O0 should not do any optimisations so dead code should not be eliminated but perhaps I am wrong.

推荐答案

如果您在代码 gcc 上未使用任何方法，智能功能可以识别此方法，并在编译应用程序时忽略它。这就是为什么当您显示该方法未显示在结果上的应用程序的符号（使用 nm ）。

If you have a method that is not used anywhere on the code gcc smart features can identify this and ignore it while compiling your application. That's why when you display the symbols (using nm) of the application that method doesn't show on the results.

想要强制该方法编译无论如何你需要指定 _ 属性 _ used strong>上的方法声明。例如：

However, if you want to force that method to be compiled anyway you need to specify the _attribute_ used on the method declaration. For instance:

  1 
  2 #include <iostream>
  3 #include <stdio.h>
  4 
  5 
  6 class aClass
  7 {
  8     public:
  9         void __attribute__ ((used)) publicPrint()
 10         {
 11             std::cout << "public method" << std::endl;
 12         }
 13 };
 14 
 15 
 16 int main()
 17 {
 18     aClass my_obj;
 19 
 20     getchar();
 21 }

< -g ：

g++ -g print_dbg.cpp -o print_dbg

我想说的可能是不必要的，但我会这样做：注意 my_obj 被声明为main（）中的局部变量。这意味着我只能访问方法 publicPrint（），而我在这个范围内调试代码。当代码执行跳转到getchar（）的开头时，代码执行将在另一个范围，即另一个堆栈帧，并且 my_obj 将不再存在于这个新的上下文中。

What I'm about to say is probably unnecessary, but I'll do it anyway: notice that my_obj is declared as a local variable inside main(). This means I only have access to the method publicPrint() while I'm debugging code inside this scope. When the code execution jumps to the beginning of getchar(), code execution will be at another scope, i.e. another stack frame, and my_obj will no longer exist in this new context. This is just a heads up.

在gdb上，如果你设置了一个断点 my_obj 有效，您可以通过执行方法 publicPrint（）：call my_obj.publicPrint（）

On gdb, if you set a breakpoint where my_obj is valid, you can execute the method publicPrint() through: call my_obj.publicPrint()

$ gdb print_dbg 
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 "i486-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/karl/workspace/gdb/print_dbg...done.

(gdb) list main
12              }
13      };
14
15
16      int main()
17      {
18          aClass my_obj;
19
20          getchar();
21      }
(gdb) break main
Breakpoint 1 at 0x804871d: file print_dbg.cpp, line 20.

(gdb) run
Starting program: /home/karl/workspace/gdb/print_dbg 
Breakpoint 1, main () at print_dbg.cpp:20
20          getchar();

(gdb) call my_obj.publicPrint()
public method

(gdb)

这篇关于使用gdb调用printDebug方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！