Writing your C++23 Code

You must already have VS Code installed, or be using a CSIL machine. If not, please see the guides.

Configure VS Code and Compiler (done once)

1. If needed, in the Explorer view on the left, create a new folder for your activity (such as lab1 or asn2; don't put spaces in these names).
   • In the Explorer pane on the left, select the "Create Folder" button at the top.
   • Name the folder based on what you are working on, such as lab1, or lecture_week_2
   • Creating folders for your work helps organize all your files; don't put spaces in the filename
2. Open/Create file:
   • Right-click on your lab1 folder (or whatever name you gave it) and select "New File"
   • Name the file as needed, such as hello.cpp.
   • Click on the file you created to open it.

3. Type in your C++ code into your file:

   CPPCopy

   #include <print>
   using namespace std;
   
   int main() {
       println("Hello world!");
   }
   

4. Configure VS Code to use C++23
   • In VS Code's menu, goto File > Preferences > Settings.
   • Search for standard
   • You should see the option: C_Cpp › Default: Cpp Standard.
   • Set this to be c++23
   • Click the X to close the preferences window.
5. Select correct C++ compiler
   • Ensure you are viewing hello.cpp.
   • From the menu, select Run > Run Without Debugger.
   • In the box at the top, select the option for "g++-14".
     
   • Notice that this will have created the file .vscode\tasks.json.
   • It is likely that compiling failed; we'll fix that in the next step.
6. Configure C++ Compiler to use C++23
   • Open .vscode/tasks.json created automatically by the previous step.
   • Ensure that the "command" line uses g++-14:
     "command": "/usr/bin/g++-14",
   • Add the following as a new line just below "args": [" list, add:
     "-std=c++23",
   • Full .vscode/tasks.json may look like:
     YAMLCopy

     {
     "tasks": [
         {
             "type": "cppbuild",
             "label": "C/C++: g++-14 build active file",
             "command": "/usr/bin/g++-14",
             "args": [
                 "-fdiagnostics-color=always",
                 "-g",
                 "${file}",
                 "-o",
                 "${fileDirname}/${fileBasenameNoExtension}"
             ],
             "options": {
                 "cwd": "${fileDirname}"
             },
             "problemMatcher": [
                 "$gcc"
             ],
             "group": {
                 "kind": "build",
                 "isDefault": true
             },
             "detail": "Task generated by Debugger."
         }
     ],
     "version": "2.0.0"
     }
     

7. Reopen the hello.cpp file.
   • It may still show an error with println because the previous attempt to compile the file failed. That's OK. We'll fix it next.
8. In the top-right of the .cpp file, click the play button.
   • Button may show a bug icon on a play button. OK to click the button, or click the drop-down and select "Debug C/C++ File".
   • It should open a new terminal (or two) and show you the output of your program.
   • If asked to "Select a debug configuration", select the "C/C++: g++-14..." option.
   • You may need to switch to the "Terminal" tab:
     
9. Rather than clicking the button each time, I suggest using CTRL-F5 (or Command-F5?) to run your program faster!

Coding Next Time

The next time you open VS Code, you won't need to set any preferences or edit tasks.json: just create a new .cpp file and select to run it!

Coding Troubleshooting

• Ensure you have your .cpp file open and are clicked into it before trying to build or run the file. For example, trying to build and run a .json file will fail.
• 'println' is underlined, VS Code says "identifier 'println' is undefined" even before compiling it.
  • See directions above for configure VS Code to use C++23: setting preferences for c++23.
• 'println' is underlined, VS code says "'println' was not declared in this scope (gcc)".
  • .vscode/tasks.json is likely missing the arg: "-std=c++23",
  • See directions above for tasks.json
• If you don't see the play button to run your code:
  • Ensure you have C++ IntelliSense addon installed in VS Code under WSL
  • Ensure you have your .cpp file open.
  • Ensure your file's name ends with .cpp.
  • Right-click on the "..." in the top right of pane showing your .cpp code and ensure there is a check-mark beside "Run or Debug..."
  • Ensure you are running WSL2
  • Ensure you have installed g++ and gdb into WSL
  • If you still don't see the play button, try installing the "Code Runner" extension. It has worked for some students.
• If you are having trouble with configuration:
  • Ensure that you initially opened your cmpt130 folder, and not a sub-folder like labs or .devcontainer.
  • Try deleting the .vscode folder and repeating configuration steps. Ensure you are selecting the g++ option, instead of the gcc option; and select g++-14 when possible.