EECS 280 Tutorials

Setup up VS Code for C/C++ on macOS

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.

This tutorial is specific to macOS. Looking for the Windows version?

Prerequisites

VS Code relies on external command line tools. To install CLI tools, follow the macOS command line tools tutorial.

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

$ g++ --version
Apple clang version 13.1.6 (clang-1316.0.21.2.5)
$ lldb --version
Apple Swift version 5.6.1 (swiftlang-5.6.0.323.66 clang-1316.0.20.12)

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

Install

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

Open VS Code. You can find it in your applications (look for “Visual Studio Code”) or, alternatively, you can run it using the command line.

$ code

Microsoft C++ Extension

Install the Microsoft C/C++ extension. On macOS, this extension provides Intellisense. See the C/C++ extension alternatives section for details about our macOS extension recommendations.

Note that you need the “C/C++” extension. You do not need the “C/C++ Extension Pack”.

1. Open the extensions panel from the left sidebar.
2. Search for C++.
3. Click “Install”.

CodeLLDB Extension

Install the CodeLLDB extension. On macOS, this extension provides debugging support. See the C/C++ extension alternatives section for details about our macOS extension recommendations.

1. Open the extensions panel from the left sidebar.
2. Search for CodeLLDB.
3. Click “Install”.

Clear out the search bar in the extensions panel. Under the “Installed” section, you should see:

• C/C++
• CodeLLDB

Create a project

To create a VS Code project, create a folder (directory). There are many ways to create folders: Finder, 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 (Terminal on macOS).

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

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. Save the updated file.

#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.hpp
├── stats.hpp
├── 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

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.

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 terminal window at the bottom.

$ 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.

Edit the "env" property in your launch.json. If there’s already an empty "env": {}, replace it. If there isn’t one, add it after the "args" property.

  "env": {
      "ASAN_OPTIONS": "abort_on_error=1:detect_leaks=0"
  },

Open Settings on VSCode (Code > Settings > Settings). Search for “lldb: show disassembly” (without the quotes) and set the option to never. (See ASAN error shows assembly code for an explanation.)

Input redirection

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

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.

Reset

To reset VS Code project settings and starter files, first quit VS Code. Make a backup copy of 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

VS Code has a lot of settings and extensions. You can reset the entire user interface and remove all extensions using these commands (Based on Microsoft instructions). This is optional.

$ rm -rf ~/.vscode
$ rm -rf ~/Library/Application\ Support/Code

Then, return to the Create a project section.

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 cmd + shift + P. 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.

ASAN error shows assembly code

When the Address Sanitizer detects an error, VSCode may stop in an assembly file that does not help you find where the error was caused. For example, consider the following code with a use-after-free error.

#include <iostream>
using namespace std;

int main() {
    int * p = new int;
    delete p;
    cout << *p << endl;  // use-after-free
}

Running the debugger with the ASAN sanitizer will display a confusing assembly file.

To disable this pop up, you can set the lldb.showDisassembly option to never.

First, open Settings on VSCode (Code > Settings > Settings).

Next, search for “lldb: show disassembly” and set the option to never.

Now, running the debugger will not display the assembly file. However, it will not yet highlight the erroneous line. To find the erroneous line, look through the Call Stack on the debugging panel and click on your source file.

Debugging fails

Sometimes on older Macs with an Intel chip or following an update, debugging in VS Code fails due to an incompatible bundled debugserver bug report.

First, make sure you have the Xcode command line tools installed. (They should already be installed.)

$ xcode-select --install

Delete the incompatible file that comes bundled with CodeLLDB.

$ rm ~/.vscode/extensions/vadimcn.vscode-lldb-*/lldb/bin/debugserver

Restart VS Code.

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.