在使用 gdb 调试 C++ 代码时，如何通过索引获得特定的 std::map 值？

Question

我使用 Ubuntu 20.04-LTS 和 WSL（Windows 子系统 Linux），GDB 版本是 9.2，我用 c++11 构建了我的 c++ 代码。

我试图通过 GDB 中的索引访问 std::map 的值，但是 GDB 显示错误消息“无效转换”。

下面我的代码是一样的

#include <iostream>
#include <map>
#include <string>

using std::cout;
using std::map;
using std::string;
using std::to_string;

int main()
{
    map<string, int> si;

    for(int i = 0; i < 10; ++i)
    {
        si[to_string(i)] = i;
    }

    for(int i = 0; i < 10; ++i)
    {
        cout << si[to_string(i)] << "\n";
    }
}

并且，在 GDB 中

GNU gdb (Ubuntu 9.2-0ubuntu1~20.04) 9.2
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Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
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    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ctest...
(gdb) l main
6       using std::map;
7       using std::string;
8       using std::to_string;
9
10      int main()
11      {
12              map<string, int> si;
13
14              for(int i = 0; i < 10; ++i)
15              {
(gdb) l 15
10      int main()
11      {
12              map<string, int> si;
13
14              for(int i = 0; i < 10; ++i)
15              {
16                      si[to_string(i)] = i;
17              }
18
19              for(int i = 0; i < 10; ++i)
(gdb) b 18
Breakpoint 1 at 0x2579: file ctest.cpp, line 19.
(gdb) r
Starting program: /home/lksj/ctest

Breakpoint 1, main () at ctest.cpp:19
19              for(int i = 0; i < 10; ++i)
(gdb) p si["1"]
Invalid cast.
(gdb)

如何在 GDB 中直接使用索引访问 std::map 对象值？

Answer 1

您首先在“.gdbinit”文件中编写以下代码。

define newstr
set ($arg0)=(std::string*)malloc(sizeof(std::string))
call ($arg0)->basic_string()
# 'assign' returns *this; casting return to void avoids printing of the 
struct.
call (void)( ($arg0)->assign($arg1) )
end

define delstr
call ($arg0)->~basic_string(0)
#                           ^
call free($arg0)
set ($arg0)=(void*)0
end

然后在您的 C++ 代码中编写以下函数。

void indexing_map( map<string,[type]> & m, string i )
{
    cout << m[i] << "\n";
}

现在，万事俱备。您只需执行 gdb 以使用

调试您的代码

newstr $foo [any string of map of the key]

例如，

example.cpp

#include <iostream>
#include <unordered_map>
#include <string>

using std::cout;
using std::unordered_map;
using std::string;

void indexing_map(unordered_map<string, int> &m, string i)
{
   cout << m[i] << "\n";
}

int main()
{
    unordered_map<string, int> st_in;
    st_in["1"] = 1;
    st_in["2"] = 2;
    st_in["3"] = 3;

    indexing_map(st_in, "1");

    return 0;
}

和 gdb

(gdb) b 25
Breakpoint 1 at 0x28d6: file ctest.cpp, line 25.
(gdb) r
Starting program: /home/user/ctest
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Breakpoint 1, main () at ctest.cpp:25
25          st_in["3"] = 3;
(gdb) newstr $foo "1"
(gdb) call indexing_map(st_in , *$foo)
1

在使用 gdb 调试 C++ 代码时，如何通过索引获得特定的 std::map 值？

How can I get specific std::map value with indexing while using gdb for debuggin c++ code?

c++

gdb

stdmap