Using debugging is essential to catch elusive bugs! This page explain how to debug in command line, Visual Studio, and VSCode.

To debug, you have to compile your program in debug mode. Visual Studio and VSCode will do it per default. To compile in debug in command line, run in your build folder cmake -DCMAKE_BUILD_TYPE=Debug ...

Debugging in command line

Run a program

The program used to debug c++ code is called gdb. You can run gdb -h to get summary of the command usage and on linux you can run man gdb to access the manual entry for gdb.

  • Open a terminal (Powershell on Windows, any on Linux and MacOS)
  • run ‘gdb `

You will enter an interactive debugging session:

GNU gdb (Ubuntu 12.1-0ubuntu1~22.04.2) 12.1
Copyright (C) 2022 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-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from cpg_test...
(gdb)
  • To run the program type run, to run with arguments type run arg1 arg2 ...
  • The program will run until it finishes, if the program crashes you will be able to inspect the call stack and the variables.
  • To inspect the call stack type: backtrace or bt, then to navigate the call stack type up or down
  • To inspect a variable type print <variable name> or explore <variable name>

You can also directly start gdb with arguments with gdb --args <your_program> arg1 arg2 ...

Set breakpoints

  • To add a breakpoint, before running the program, type break <line number> or `break .
  • After running the program, the execution will pause at the set breakpoint. You can inspect the call stack and variables with same commands described in the previous section.
  • To continue the execution simply type continue
  • To continue the execution until a certain line, type until <line number>.
  • After a break, you can also execute the program step by step by typing step

While debugging always pay attention in which file you currently are.

In the interactive session, you can type help to get the list of command classes.

List of classes of commands:

aliases -- User-defined aliases of other commands.
breakpoints -- Making program stop at certain points.
data -- Examining data.
files -- Specifying and examining files.
internals -- Maintenance commands.
obscure -- Obscure features.
running -- Running the program.
stack -- Examining the stack.
status -- Status inquiries.
support -- Support facilities.
text-user-interface -- TUI is the GDB text based interface.
tracepoints -- Tracing of program execution without stopping the program.
user-defined -- User-defined commands.

For instance, if you type help breakpoints, you will get the list of the breakpoints commands.

Debugging in Visual Studio

You can refer to this page

To start debugging, type F5 or select Debug > Start Debugging. You can set breakpoint with a right click on the line where you want stop and select breakpoint > insert breakpoint.

Debugging in VSCode

image You can refer to this page

  • Open the source file that you want to debug
  • You can set breakpoints by clicking the editor margin to the lines you want the execution to stop.
  • Start debugging with F5, or open the Run and Debug view (Ctrl+Shift+D) and select Run and Debug.
  • If prompted, select the debugger for your language or runtime. Per default VSCode will run the active file. You can create a launch.json file in .vscode folder to create custom configuration such as this one: 
      {
  // Use IntelliSense to learn about possible attributes.
  // Hover to view descriptions of existing attributes.
  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
  "version": "0.2.0",
  "configurations": [
      {
          "name": "(gdb) Launch",
          "type": "cppdbg",
          "request": "launch",
          "program": "/home/leni/git/AREFramework/build/simulation/are-client",
          "args": ["/home/leni/git/AREFramework/experiments/me2im/parameters.csv", "10000", "1"],
          "stopAtEntry": false,
          "cwd": "${fileDirname}",
          "environment": [],
          "externalConsole": false,
          "MIMode": "gdb",
          "setupCommands": [
              {
                  "description": "Enable pretty-printing for gdb",
                  "text": "-enable-pretty-printing",
                  "ignoreFailures": true
              },
              {
                  "description": "Set Disassembly Flavor to Intel",
                  "text": "-gdb-set disassembly-flavor intel",
                  "ignoreFailures": true
              }
          ]
          }
  ]
  }
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