EECS 280 Tutorials

Setup up VS Code for C/C++

Visual Studio Code is a lightweight, easy-to-use, source code editor with debugging support. It runs on macOS, Windows, and Linux (including CAEN Linux). Visual Studio Code is not the same program as Visual Studio.

Prerequisites

VS Code relies on external command line tools. If you haven’t installed CLI tools on your machine yet, follow one of these tutorials first.

Make sure you have a compiler and a debugger installed. Your version might be different. Instructions for installation on macOS, Windows/WSL/Linux.

$ g++ --version  # macOS
Apple clang version 13.1.6 (clang-1316.0.21.2.5)
$ lldb --version # macOS
Apple Swift version 5.6.1 (swiftlang-5.6.0.323.66 clang-1316.0.20.12)
$ g++ --version  # WSL/Linux
g++ (GCC) 8.5.0 20210514
$ gdb --version  # WSL/Linux
GNU gdb (GDB)

Next, follow our Command line interface (CLI) tutorial.

Restart

To start clean, first quit VS Code. Back up your files, and then delete your project directory. Your project directory might be different.

$ pwd
/Users/awdeorio/src/eecs280
$ cp -a p1-stats p1-stats.bak  # Backup
$ rm -rf p1-stats              # Delete

Install

Choose your platform below. Also make sure to install extensions.

Linux

Install the .deb package from the web https://code.visualstudio.com/docs/setup/linux.

CAEN Linux

VS Code is already installed on CAEN Linux desktop environment. You can use it while sitting at a CAEN Linux computer, or through a VNC connection to CAEN Linux.

macOS

Make sure you have macOS 11.1 or later.

$ sw_vers
ProductName:	macOS
ProductVersion:	11.7

Use the homebrew package manager to install VS Code. You can run this command from any directory.

$ brew install --cask visual-studio-code

Windows

Make sure you have updated Windows and WSL installations according to the WSL tutorial.

Then, Install VS Code from the web https://code.visualstudio.com/.

Select “Add to PATH”.

Reboot. Open a terminal again (WSL/Ubuntu) and verify your installation. Your version might be different.

$ code --version
1.74.1
1ad8d514439d5077d2b0b7ee64d2ce82a9308e5a
x64

Extensions

Make sure VS Code is installed correctly by checking the version. You need version 1.52.1 or higher.

$ code --version
1.52.1

macOS

Install the Microsoft C/C++ extension and the CodeLLDB extension. See the C/C++ extension alternatives section for details about why we recommend these extensions.

$ code --install-extension ms-vscode.cpptools
$ code --install-extension vadimcn.vscode-lldb

Restart VS Code.

Verify that the extensions are installed. It’s OK if you have other extensions installed.

$ code --list-extensions
ms-vscode.cpptools
vadimcn.vscode-lldb

Windows

Install the Microsoft C/C++ extension and the WSL extension. See the C/C++ extension alternatives section for details about why we recommend these extensions.

$ code --install-extension ms-vscode.cpptools
$ code --install-extension ms-vscode-remote.remote-wsl

Restart VS Code.

Verify that the extension is installed. It’s OK if you have other extensions installed.

$ code --list-extensions
ms-vscode.cpptools
ms-vscode-remote.remote-wsl

Create a project

To create a VS Code project, create a folder (directory). There are many ways to create folders: Finder AKA File Explorer, VS Code interface, VS Code integrated terminal, and the system terminal. We’ll use the system terminal and call our example project p1-stats.

Open the Terminal (macOS) or Ubuntu Bash Shell (Windows).

Navigate to your home directory, create a new directory, then move into the new directory. Your folder location might be different. Here’s some help with cd, the tilde ~, and mkdir.

$ mkdir ~/eecs280
$ cd ~/eecs280
$ mkdir p1-stats
$ cd p1-stats

$ pwd
/home/awdeorio ...         # Good, Linux home
/c/mnt/Users/awdeorio ...  # Bad, Windows home

Start VS Code and open your project folder by selecting File > Open Folder... > navigate to the p1-stats folder.

$ ls
main.cpp ...
$ code .

Add new files

Open your project folder by selecting File > Open Folder... > navigate to the p1-stats folder.

Select the add file icon and give it a name, e.g., main.cpp.

Alternatively, create your main.cpp file from the command line using touch.

$ touch main.cpp

Copy-paste this Hello World program into your main.cpp.

#include <iostream>
using namespace std;

int main() {
  cout << "Hello World!\n";
}

Add existing files

If you have starter files, add them to your project directory. This example is from EECS 280 Project 1, but this tutorial doesn’t require understanding the files. Your URL or files might be different.

$ ls
main.cpp

We’ll use the terminal to download, unpack, and move the starter files into the directory that already contains main.cpp. Your URL or folder might be different.

$ wget https://eecs280staff.github.io/p1-stats/starter-files.tar.gz
$ tar -xvzf starter-files.tar.gz
$ mv starter-files/* .
$ rm -rf starter-files starter-files.tar.gz

You should see your new files in your project directory.

$ tree
.
├── Makefile
├── main.cpp
├── main_test.in
├── main_test.out.correct
├── main_test_data.tsv
├── p1_library.cpp
├── p1_library.h
├── stats.h
├── stats_public_test.cpp
└── stats_tests.cpp.starter

You should see your new files appear in VS Code.

Rename files

If you need to rename any files, you can do this from VS Code or from the command line. In EECS 280, you’ll need to rename any files that end in .starter.

Right click a file and select “rename”. Change the file name. In EECS 280, you’ll do this to any file that ends in .starter.

$ mv stats_tests.cpp.starter stats_tests.cpp

Compile and Run

VS Code uses an executable you build at the command line.

First, compile and run your executable at the command line.

$ touch stats.cpp  # Needed for EECS 280 P1
$ make main.exe
$ ./main.exe
Hello World!

$ ls
main.cpp ...

$ make main.exe
make: *** No rule to make target `stats.cpp', needed by `main.exe'.  Stop.

$ make main.exe
g++ ... -g main.cpp ...

$ g++ -g main.cpp -o main.exe

macOS create launch.json

Select the file you would like to run. Navigate to the debugging pane.

Click “create a launch.json file”.

Select LLDB.

Edit the program field in launch.json. Save the updated file. Your program name might be different.

Windows/WSL create launch.json

Select the file you would like to run. Navigate to the debugging pane.

Click “create a launch.json file”.

Select C++ (GDB/LLDB).

Click “Add Configuration”.

Select the “C/C++ (gdb) Launch” configuration. This will create a default launch.json (Microsoft Reference).

Edit the program and cwd fields in launch.json. Save the updated file. Your program name might be different.

Edit launch.json program

If you already have a working launch.json and want to debug a different program, edit the program field launch.json. Your program name might be different. Make sure cwd is set to "${workspaceFolder}".

{
    "program": "${workspaceFolder}/main.exe",
    ...
    "cwd": "${workspaceFolder}",
}

Run

Click the triangle to run. You’ll see your program’s output in the debug console.

$ make main.exe

Sanitizers

We recommend enabling the address sanitizer and undefined behavior sanitizer. These will help you find memory errors like going off the end of an array or vector.

First, edit your Makefile and add the CXXFLAGS recommended by the ASAN Quick Start.

Then, edit the "environment" property in your launch.json. If there’s already an empty "environment": [], replace it.

  "environment": [
    {
      "name": "ASAN_OPTIONS",
      "value": "abort_on_error=1:detect_leaks=0"
    }
  ]

When ASan detects an error, VSCode will stop so that you can see the stack trace and inspect the current state of the program. This configuration also turns off leak-checking (LSan), which can’t run simultaneously with the visual debugger. If you do want to check for leaks, just run from the terminal with sanitizers enabled.

If you’re debugging something else in your program and don’t want it to terminate on ASAN errors, you can change to abort_on_error=0.

Input redirection

If you’re unfamiliar with input redirection, first read the CLI tutorial section on input redirection.

Windows/WSL or Linux launch.json changes

To configure input redirection, edit launch.json. These changes are for the Microsoft C/C++ extension.

{
    "configurations": [
        {
            ...
            "program": "${workspaceFolder}/main.exe",
            "args": ["<", "main_test.in"],
            ...
        }
    ]
}

macOS launch.json changes

To configure input redirection, edit launch.json (docs). These instructions are for the CodeLLDB extension.

{
    "configurations": [
        {
            ...
            "program": "${workspaceFolder}/main.exe",
            "stdio": ["main_test.in", null, null],
            ...
        }
    ]
}

{
    "configurations": [
        {
            "type": "lldb",
            ...

Arguments and options

Arguments and options are inputs to a program typed at the command line. Here’s an example from EECS 280 Project 5:

$ ./main.exe train_small.csv test_small.csv --debug

• main.exe is the name of the program
• train_small.csv and test_small.csv are arguments
• --debug is an option

To run a program with options or arguments in VS Code, edit launch.json. Each option or argument should goes in a separate comma-separated string.

{
    "configurations": [
        {
            ...
            "program": "${workspaceFolder}/main.exe",
            "args": ["train_small.csv", "test_small.csv", "--debug"],
            ...
        }
    ]
}

Debug

In this section, we’ll set a breakpoint, which pauses the debugger. Then, we’ll cover some of the options to continue execution.

Step Over Run one line of code, stepping over any function calls by running the whole function in one step.

Step Into Run one line of code, stepping into any function calls to execute them line-by-line.

Step Out Run the program until it returns from the current function (or until the next breakpoint).

Continue Run the program until the next breakpoint.

Example code

To get started, copy this example main.cpp into your editor.

#include <iostream>
#include <vector>
using namespace std;

double sum (const vector<double> &data) {
  double total = 0;
  for (size_t i=0; i<data.size(); ++i) {
    total += data[i];
  }
  return total;
}

int main() {
  vector<double> data;
  data.push_back(10);
  data.push_back(20);
  data.push_back(30);
  cout << "sum(data) = " << sum(data) << endl;
}

Breakpoint

Select the file you want to debug. Set a breakpoint by clicking to the left of a line number. A breakpoint tells the program to pause.

Run

Select the debugging pane, then run the debugger. The program pauses at the breakpoint. The yellow indicator highlights the next line of code to be run.

$ make main.exe                # With a Makefile
$ g++ -g main.cpp -o main.exe  # Without a Makefile

Step over

Click “Step Over” a few times until you reach the highlighted line of code

Inspect

Hover over a variable to inspect its value. You can also see values in the VARIABLES pane.

Step into

Click “Step Into”. The cursor enters the sum() function.

Step out

Click “Step Out”. The sum() function completes, and the program pauses again.

Continue

Press “Continue” to run the program to the next breakpoint, or the end, whichever comes first.

Troubleshooting

This section is for common problems and solutions.

Compile and run

If you have trouble with the compile and run section, a good first step is to delete your launch.json and try the compile and run section again.

Intellisense C++ Standard

Intellisense is the feature that indicates compiler errors with red squiggly lines and suggests code completions. If the C++ standard is out-of-date, you’ll see squiggles where you shouldn’t.

First, you should already have the C/C++ extension installed (Instructions).

Next, open VS Code’s Command Palette with View > Command Palette or with the keyboard shortcut ctrl + shift + P on Windows or cmd + shift + P on macOS. Search for and select C/C++: Edit Configurations (JSON). This will open the file c_cpp_properties.json.

Modify the cStandard and cppStandard settings in c_cpp_properties.json. Don’t change any other settings. Save the file.

{
    "configurations": [
        {
            ...
            "cStandard": "c17",
            "cppStandard": "c++17",
            ...
        }
    ],
    ...
}

C/C++ extension alternatives

There are multiple options for C/C++ extensions.

Microsoft C/C++ extension provides debugging support and intellisense on Windows, Linux and macOS. At the time of this writing (January 2023) debug support has a bug on macOS.

CodeLLDB provides debugging support for those using the LLVM compiler. Apple’s compiler on macOS is based on LLVM.

clangd provides intellisense and requires the clangd language server, which is related to the LLVM compiler. We do not recommend installing the clangd extension with the Microsoft C/C++ extension because multiple intellisense providers can produce confusing results.

WSL lets us develop with Linux-based utilities like the g++ compiler.

Acknowledgments

Original document written by Andrew DeOrio awdeorio@umich.edu.

This document is licensed under a Creative Commons Attribution-NonCommercial 4.0 License. You’re free to copy and share this document, but not to sell it. You may not share source code provided with this document.