GDB - Basic Setup

Learning Outcome

Able to confirm GDB is available in your command line environment, and install it if required. (Optionally configure VSCode to use GDB for debugging)

Applicable subjects

COMP1521, COMP2521

Note: COMP3231 has its own specific setup

Check if GDB is installed

The which command can be used to test if gdb is available in your environment. It returns the path where gdb is installed as shown below. If it returns nothing, gdb is not in your environment, so continue to the next section.

$ which gdb
/usr/bin/gdb
$

GDB on Commandline Setup (Linux and WSL)

GDB should be already installed on the CSE systems.

If it is not installed on your linux distribution, run the following commands:

$ sudo apt-get update
$ sudo apt-get install gdb

GDB in VSCode Setup

VSCode can be used as front end to GDB that provides a convenient environment to execute and debug your code directly in the editor.

Note some level of VSCode familiarity is assumed in the following instructions.

  1. Install the C/C++ Intellisense extension

  2. Add the following two JSON files to the .vscode directory. WSL users may have to change these files.

launch.json
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{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "gcc build and debug active file",
            "type": "cppdbg",
            "request": "launch",
            "program": "${fileDirname}/${fileBasenameNoExtension}",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ],
            "preLaunchTask": "gcc build active file",
            "miDebuggerPath": "/usr/bin/gdb"
        }
    ]
}
tasks.json
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{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "gcc build active file",
            "command": "gcc",
            "args": ["-Wall", "-Werror", "-std=c99", "-g", "-o", "${fileDirname}/${fileBasenameNoExtension}", "${fileDirname}/${fileBasename}"]
        }
    ]
}

  1. Now you should be able to use the debugging features in VSCode, which are found by clicking on the bug icon on the left of the screen.

Mac Setup

There are two options for mac users:

1. Install using brew

This is very difficult. There are instructions available online.

2. Use lldb

lldb is a debugger with similar functionality to gdb. It comes pre-installed on mac computers. A conversion table from gdb to lldb commands is available here

Module author: Liz Willer <e.willer@unsw.edu.au>

Date

2020-01-15