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Quick Setup (using CMake)

Learning Objective:
In this short guide you will learn how to set up SeqAn and how to compile a small example to test whether everything works.

Difficulty | Easy
Duration | 30 Minutes
Prerequisite tutorials | No prerequisites
Recommended reading |

# Software

Requirements:

- gcc >= 12 or clang >=17 or IntelOneAPI >= 2024.0
- cmake >= 3.20
- git

## Installing a compiler

VisualStudio/MSVC is not yet supported. We will briefly explain how to install a compiler on some popular operating systems. We recommend using the latest version of the compiler. For more information, refer to your operating system's documentation.

### GCC

#### Linux

- Ubuntu without PPA
  # Ubuntu 24.04
  sudo apt install g++-14
  # Ubuntu 22.04
  sudo apt install g++-12
- Ubuntu with PPA
  sudo add-apt-repository --no-update --yes ppa:ubuntu-toolchain-r/ppa
  sudo add-apt-repository --no-update --yes ppa:ubuntu-toolchain-r/test
  sudo apt-get update
  sudo apt install g++-14
- Using conda To avoid interference with system packages, we recommend creating a new environment when using conda.
  conda create -n conda_gcc_env -c conda-forge gcc_linux-64
  conda activate conda_gcc_env
  This will put GCC in a separate environment conda_gcc_env which can be activated via conda activate conda_gcc_env and deactivated via conda deactivate.

#### macOS

- Using Homebrew
  brew install gcc@14
- Using Macports
  sudo port install gcc14

### Clang

#### Linux

- Ubuntu 24.04
  # Ubuntu 24.04
  sudo apt install clang-18
- Ubuntu with PPA Refer to https://apt.llvm.org/

#### macOS

- Using Homebrew
  brew install llvm@19
- Using Macports
  sudo port install clang-19

### Windows

The Windows Subsystem for Linux offers an easy way to run a Linux distribution under Windows. Follow Microsoft's setup guide to install WSL and then follow the steps listed for Linux-based systems.

### Browser

- Using gitpod.io gitpod.io allows you to edit, compile and run code from within your browser. The free version includes 50 hours of use per month, which is plenty for our tutorials. A GitHub account is required. Click here to open SeqAn3 in gitpod.
- Using GitHub Codespaces GitHub Codespaces offer a service similar to gitpod, including a free monthly quota. Click here to open SeqAn3 in Codespaces.

Attention
  After installing, g++ --version should print the desired GCC version. If not, you may have to use, for example, g++-14 --version or even specify the full path to your compiler.

Similarly, you may need to install CMake and git, e.g. apt install cmake git.

# Directory Structure

In this section we will use the tree command to show the directory structure. This program may not be installed on your system. If so, you may wish to install it or verify the directory structure in other ways, e.g. by using ls -l.

For this project, we recommend following directory layout:

tutorial
├── source
├── build
└── seqan3

To set these directories up you can follow this script:

mkdir tutorial
cd tutorial
mkdir build
mkdir source
git clone https://github.com/seqan/seqan3.git

The output of the command tree -L 2 should now look like this:

.
├── build
├── seqan3
│ ├── CHANGELOG.md
│ ├── CMakeLists.txt
│ ├── ...
│ └── test
└── source
8 directories, 6 files

# Compiling and Running

To test whether everything works, we will now compile and run a small example.

First we create the file hello_world.cpp in the source directory with the following contents:

// SPDX-FileCopyrightText: 2006-2025 Knut Reinert & Freie Universität Berlin
// SPDX-FileCopyrightText: 2016-2025 Knut Reinert & MPI für molekulare Genetik
// SPDX-License-Identifier: BSD-3-Clause
#include <seqan3/core/debug_stream.hpp>
int main()
{
seqan3::debug_stream << "Hello World!\n";
return 0;
}
debug_stream.hpp
Provides seqan3::debug_stream and related types.
seqan3::debug_stream
debug_stream_type debug_stream
A global instance of seqan3::debug_stream_type.
Definition debug_stream.hpp:38

To compile it, we first create a CMakeLists.txt file in the source directory:

cmake_minimum_required (VERSION 3.20...3.31)
project (seqan3_tutorial CXX)
# add seqan3 to search path
list (APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../seqan3/cmake")
# require seqan3 with a version between >=3.0.0 and <4.0.0
find_package (seqan3 3.0 REQUIRED)
# build app with seqan3
add_executable (hello_world hello_world.cpp)
target_link_libraries (hello_world seqan3::seqan3)
seqan3
The main SeqAn3 namespace.
Definition aligned_sequence_concept.hpp:26

The directories should now look like this:

.
├── build
├── seqan3
│ ├── CHANGELOG.md
│ ├── CMakeLists.txt
│ ├── ...
│ └── test
└── source
├── CMakeLists.txt
└── hello_world.cpp

Now we can switch to the directory build and run:

cmake -DCMAKE_BUILD_TYPE=Release ../source
make
./hello_world

The output should be Hello World!. Note that the build type is specified with -DCMAKE_BUILD_TYPE=Release. Specifying Release enables an optimized build where no debug information is available. Release mode is therefore suitable for the end user. Programs built using -DCMAKE_BUILD_TYPE=Debug will run slower, but also make the detection of errors easier. Debug is suitable for contributors, and we recommend using it while working with our Tutorials.

Remarks
  Depending on the standard C++ compiler on your system, you may need to specify the compiler via -DCMAKE_CXX_COMPILER=, for example:
  cmake -DCMAKE_CXX_COMPILER=/path/to/executable/g++-14 ../source

# Adding a new source file to your project

If you create a new cpp file and want to compile it, you need to add another add_executable and target_link_libraries directive to you CMakeLists.txt. For example, after adding another_program.cpp your CMakeLists.txt may look like this:

cmake_minimum_required (VERSION 3.20...3.31)
project (seqan3_tutorial CXX)
# add seqan3 to search path
list (APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../seqan3/cmake")
# require seqan3 with a version between >=3.0.0 and <4.0.0
find_package (seqan3 3.0 REQUIRED)
# build app with seqan3
add_executable (hello_world hello_world.cpp)
target_link_libraries (hello_world seqan3::seqan3)
add_executable (another_program another_program.cpp)
target_link_libraries (another_program seqan3::seqan3)

# Including SeqAn3 as external project

cmake_minimum_required (VERSION 3.20...3.31)
project (my_app LANGUAGES CXX VERSION 1.0.0)
set (seqan3_git_tag "#.#.#") # adapt as needed, e.g. "3.2.0" or "main"
message (STATUS "Fetching SeqAn3 ${seqan3_git_tag}:")
include (FetchContent)
FetchContent_Declare (
seqan3_fetch_content
GIT_REPOSITORY "https://github.com/seqan/seqan3.git"
GIT_TAG "${seqan3_git_tag}"
)
# Download and make SeqAn3 available.
FetchContent_MakeAvailable (seqan3_fetch_content)
add_executable (my_app my_app.cpp)
# Set up everything needed to use SeqAn3 with my_app:
target_link_libraries (my_app PUBLIC seqan3::seqan3)

# Including SeqAn3 as external project with CPM (recommended)

See https://github.com/cpm-cmake/CPM.cmake for install instructions.

cmake_minimum_required (VERSION 3.20...3.31)
project (my_app LANGUAGES CXX VERSION 1.0.0)
include (cmake/CPM.cmake)
CPMAddPackage("gh:seqan/seqan3@3.4.0")
add_executable (my_app my_app.cpp)
# Set up everything needed to use SeqAn3 with my_app:
target_link_libraries (my_app PUBLIC seqan3::seqan3)

# Encountered issues

- Using conda's gcc package: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version 'CXXABI_1.3.11' not found
  Try setting LD_LIBRARY_PATH:
  export LD_LIBRARY_PATH=<conda_install_path>/envs/conda_gcc_env/lib/
  where <conda_install_path> must be replaced by the path yo your conda installation.
  Usually this corresponds to the path printed by conda info --base and may look similar to /home/user/miniconda3/.
- Assembler not found: ... could not understand flag m ...
  Try adding /usr/bin to your PATH:
  export PATH=/usr/bin:$PATH
  and run cmake again.
- Incorrect compiler: Your compiler is not supported. or Only GCC is supported.
  The incorrect compiler is used (e.g., Apple Clang instead of GCC). Be sure to set -DCMAKE_CXX_COMPILER=. For an example, see this remark.

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