如何使用gdb调试？

Question

我试图在我的程序中添加一个断点

b {line number}

但我总是得到一个错误,上面写着:

No symbol table is loaded.  Use the "file" command.

我该怎么办？

Answer 1

这是gdb的快速入门教程:

/* test.c  */
/* Sample program to debug.  */
#include <stdio.h>
#include <stdlib.h>

int
main (int argc, char **argv) 
{
  if (argc != 3)
    return 1;
  int a = atoi (argv[1]);
  int b = atoi (argv[2]);
  int c = a + b;
  printf ("%d\n", c);
  return 0;
}

使用-g选项编译:

gcc -g3 -o test test.c

将可执行文件(现在包含调试符号)加载到gdb中:

gdb --annotate=3 test.exe 

现在你应该发现自己在gdb提示符下.在那里你可以向gdb发出命令.假设您想在第11行放置断点并逐步执行,打印局部变量的值 - 以下命令序列将帮助您执行此操作:

(gdb) break test.c:11
Breakpoint 1 at 0x401329: file test.c, line 11.
(gdb) set args 10 20
(gdb) run
Starting program: c:\Documents and Settings\VMathew\Desktop/test.exe 10 20
[New thread 3824.0x8e8]

Breakpoint 1, main (argc=3, argv=0x3d5a90) at test.c:11
(gdb) n
(gdb) print a
$1 = 10
(gdb) n
(gdb) print b
$2 = 20
(gdb) n
(gdb) print c
$3 = 30
(gdb) c
Continuing.
30

Program exited normally.
(gdb) 

简而言之,您只需使用以下命令即可开始使用gdb:

break file:lineno - sets a breakpoint in the file at lineno.
set args - sets the command line arguments.
run - executes the debugged program with the given command line arguments.
next (n) and step (s) - step program and step program until it 
                        reaches a different source line, respectively. 
print - prints a local variable
bt -  print backtrace of all stack frames
c - continue execution.

在(gdb)提示符下键入help以获取所有有效命令的列表和描述.

Answer 2

以可执行文件作为参数启动gdb,以便它知道要调试哪个程序:

gdb ./myprogram

然后你应该能够设置断点.例如:

b myfile.cpp:25
b some_function