Become a Linux Debugging Expert: Unveiling the Secrets of GDB!

[root@hcss-ecs-a9ee ~]# cgdb --version-bash: cgdb: command not found

sudo yum install -y cgdb

1 myexe: code.c
2     gcc -o $@ $^ -std=c99 -g
3 .PHONY: clean
4 clean:
5     rm -f myexe

#include <stdio.h>
int Sum(int s, int e) {
    int sum = 0;
    int i = s;
    for(; i <= e; i++) {
        sum += i;
    }
    return sum;
}
int main() {
    printf("process is running\n");
    int start = 1;
    int end = 100;
    int result = Sum(start, end);
    printf("process is done, result: %d\n", result);
    return 0;
}

gcc test.c -o test -g -std=c99

Name    Description
l(list)    Line number/function name    Displays corresponding code, 10 lines at a time.
r(run)    F5    Runs directly without breakpoints, starts from the first breakpoint if there are any.
b(breakpoint) + line number    Sets a breakpoint at the specified line.
b source file: function name    Sets a breakpoint at the first line of the function.
b source file: line number    Sets a breakpoint at that line in the source file.
info b    View breakpoint information.
breakpoint already hit 1 time    This breakpoint has been hit once.
d(delete) + current breakpoint number    Deletes a breakpoint (cannot use d + line number). If you haven't exited gdb yet, the breakpoint numbers will continue to increment.
d + breakpoints    Deletes all breakpoints.
disable b(breakpoints)    Disables all breakpoints (default is enabled).
enable b(breakpoints)    Enables all breakpoints (default is enabled).
disable b(breakpoint) + number    Disables a specific breakpoint.
enable b(breakpoint) + number    Enables a specific breakpoint.
enable breakpoint    Enables a specific breakpoint.
n(next)    Step over (equivalent to F10).
s(step)    Step into (equivalent to F11).
bt    Displays the process of function calls (function stack).
set var    Modifies the value of a variable.
p(print) variable name    Prints the value of the variable.
display    Tracks a variable, showing its value every time it stops (variable/structure...).
undisplay + variable name number    Cancels tracking of previously set variables.

Name    Description
until + line number    Jumps to the specified position, executing the code in the interval.
finish    Executes until the current function returns, then stops and waits for a command.
c(continue)    Runs directly from one breakpoint to the next (similar to pressing F5 continuously in VS).

[lisi@hcss-ecs-a9ee lesson9]$ lscode.c  Makefile  myexe
[lisi@hcss-ecs-a9ee lesson9]$ cgdb myexe

[?1034h[?1034hGNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-120.el7
Copyright (C) 2013 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-redhat-linux-gnu".
For bug reporting instructions, please see:<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/lisi/112/lesson9/myexe...done.
(gdb) l
23          printf("process is running\n");
24          int start = 1;
25          int end = 100;
26          int result = Sum(start, end);
27          printf("process is done, result: %d\n", result);
28          return 0;
29  }(gdb)

(gdb) L  0
1  #include <stdio.h>
2  int Sum(int s, int e)
3  {
4      int sum = 0;
5      int i = s;
6      for(; i <= e; i++)
7      {
8          sum += i;
(gdb)

For gcc/g++, the default generated executable program is the 【Release】 version, so we need to add the -g command option to generate a 【Debug】 version of the executable program after make, allowing us to debug it. Then we officially entered the usage of the CGDB debugger, introducing many related commands. These are common commands I have compiled; in fact, there are many commands for CGDB, but the frequently used ones are just these. As long as you carefully study and become proficient in using them, I believe your debugging skills will significantly improve, which will also help you in debugging in VS. Finally, after learning many debugging commands for CGDB, we conducted a practical exercise on 【Swap Two Numbers】, which not only consolidated our knowledge of pass-by-address calls and function stack frames in C language but also enhanced our proficiency in using the CGDB debugger.