OxRSE Training

Introduction to VSCode

Microsoft's VSCode is a lightweight IDE which is great when starting out developing programs. It not only supports Python, but also C++, C#, JavaScript, CSS, and Java, amongst others. It's also available for Mac OS, Linux, and Windows. Whilst lightweight, it's features can be readily extended for a variety of languages via installation of plugins to suit your needs, and you can even develop your own plugins for VSCode. As well as features like live debugging and context-sensitive code autocompletion, other notable features include:

Revision/version control support: ability to work with Git source code repositories, uploading and synchronising changes to/from such repositories on e.g. GitHub. We'll be covering Git version control later in the course
Live code development sharing: without exchanging changes using version control, you can view live changes being made by another team member collaboratively within your own VSCode editor

Running VSCode for the First Time

If you haven't run VSCode yet, do this now. The first thing we need to do is open a folder to work in. Select Open Folder from the bar on the left (or from the File drop down menu at the top of VSCode), and a dialogue window will appear. Choose a new (empty) folder to work in.

Trusting Code

You may be asked whether you trust the authors of the files in this folder. Select the checkbox, and click 'Yes, I trust the authors' (although in general use some caution is recommended!)

This directory is now the current working directory for VSCode, so when we run scripts from VSCode, this will be the working directory they'll run from.

If you'd like to explore VSCode in more depth than this course offers, see the VSCode documentation.

Adding C++ VSCode extensions

VSCode has a few C++ specific extensions to help us write and compile our C++ code. Select the "Extensions" view icon on the Activity bar (far LHS of your screen, the vertical list of icons), and search for "C++". Make sure that the "C/C++" and "C/C++ Extension Pack" (by Microsoft) are installed and enabled before you proceed. There are a number of other C++ extensions also available, feel free to look through the list and try out any that you might find useful.

Ensuring you have a compiler installed

C++ source code is converted into executables that you can run using a compiler. There are a number of different C++ compilers available, and two of the most common are Clang, based on the LLVM framework or GCC, the GNU Compiler Collection.

Ensure that you have either clang or g++ (part of GCC) compiler installed using:

clang++ --version

g++ --version

You should see something like:

Homebrew clang version 15.0.3
Target: x86_64-apple-darwin22.1.0
Thread model: posix
InstalledDir: /usr/local/opt/llvm/bin

Check where the compiler executable is located on your machine

which clang++
which g++

You should see something like:

/usr/local/opt/llvm/bin/clang++

Make a note of the location of the compiler that you wish to use.

Compiling and Running a C++ executable

Let's create our first C++ program in VSCode. Select File -> New Text File from the menu. A new file will appear. Copy or type in the following contents and save the file as hello.cpp.

#include <iostream>

int main(void) {
  std::cout << "Hello, world!" << std::endl;
}

Open the command palette (F1) and choose "C/C++ Run C/C++ File", or click on the play button in the top right hand corner of the screen. Choose one of the compilers that you located earlier, and VSCode will create the file .vscode/tasks.json with the configuration used to build and run the currently active file

The file should compile successfully and output the text "hello world" in the debug console.

Open the vscode/tasks.json file created earlier, it should look something like this:

{
  "tasks": [
    {
      "type": "cppbuild",
      "label": "C/C++: g++ build active file",
      "command": "/usr/bin/g++",
      "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"
}

In "command" and "args, this file describes the command that VSCode runs to compile your code. In this case ${file} is the name of our source file hello.cpp, ${fileDirname} is the name of the directory that hello.cpp is contained in (this is the root directory of our project), and ${fileBasenameNoextension} is simply hello. So the command that is run for the tasks.json above would be:

/usr/bin/g++ -fdiagnostics-color=always -g hello.cpp -o hello

This command uses the g++ compiler to compile hello.cpp and writes the output exectable program to the file hello. You can now run this executable via the command-line and see the "Hello, world!" text written to the screen. This is just manually doing what VSCode does automatically via the tasks.json file.

Note that this command also adds debug symbols to the executable using the -g flags. This allows us to use a debugger (such as gdb or lldb) to step through our code on execution.

C++ standards

There are a number of different C++ standards with names based on the year in which they were released: C++98, C++11, C++14, C++17, C++20, and C++22. Depending on your compiler and its version, your compiler will by default use one of these. Lets make sure we are using a certain standard (in this case we will choose C++20). We can tell either g++ or clang++ to use the C++20 standard using the -std flag:

/usr/bin/g++ -std=c++20 -g hello.cpp -o hello

And we can add this to the VSCode tasks.json file like so:

{
  "tasks": [
    {
      "type": "cppbuild",
      "label": "C/C++: g++ build active file",
      "command": "/usr/bin/g++",
      "args": [
        "-fdiagnostics-color=always",
        "-std=c++20",
        "-g",
        "${file}",
        "-o",
        "${fileDirname}/${fileBasenameNoExtension}"
      ],
      "options": {
        "cwd": "${fileDirname}"
      },
      "problemMatcher": ["$gcc"],
      "group": {
        "kind": "build",
        "isDefault": true
      },
      "detail": "Task generated by Debugger."
    }
  ],
  "version": "2.0.0"
}