instructions on building CGAL libraries from source code

Building CGAL from Source: A Comprehensive Guide for C++ Developers

Learn how to compile and install the Computational Geometry Algorithms Library (CGAL) from source code on your system, covering prerequisites, CMake configuration, and common build issues.

CGAL (Computational Geometry Algorithms Library) is a powerful C++ library that provides robust and efficient geometric algorithms and data structures. While pre-compiled binaries are sometimes available, building CGAL from source offers greater flexibility, allowing you to customize build options, link against specific versions of dependencies, and integrate it seamlessly into your development environment. This guide will walk you through the process step-by-step, ensuring a successful build on most Unix-like systems and Windows.

Prerequisites and Dependencies

Before you begin compiling CGAL, you need to ensure that your system has the necessary tools and libraries installed. CGAL relies on several external dependencies for its full functionality. The core requirements are a C++ compiler, CMake for build system generation, and Boost. Other optional dependencies enhance CGAL's capabilities, such as Qt for visualization or MPFR/GMP for arbitrary precision arithmetic.

flowchart TD
    A[Start] --> B{Install C++ Compiler (GCC/Clang/MSVC)}
    B --> C{Install CMake}
    C --> D{Install Boost Libraries}
    D --> E{Optional: Install Qt, MPFR, GMP}
    E --> F[Download CGAL Source]
    F --> G[Configure with CMake]
    G --> H[Build CGAL]
    H --> I[Install CGAL]
    I --> J[End]

CGAL Build Process Flow

Step-by-Step Build Instructions

This section details the process of downloading, configuring, building, and installing CGAL from its source code. We'll primarily use CMake for configuration, which is the recommended approach for CGAL.

1. 1. Download CGAL Source Code

Obtain the latest stable release of CGAL from its official website or GitHub repository. It's recommended to use a stable release rather than the development branch for most projects.

2. 2. Create a Build Directory

Navigate to the downloaded CGAL source directory and create a separate build directory. This keeps your source tree clean and makes it easier to manage different build configurations.

3. 3. Configure with CMake

From within your build directory, run CMake to configure the build system. You'll need to specify the path to the CGAL source directory and can optionally set various build flags. Common flags include CMAKE_INSTALL_PREFIX to define the installation path and WITH_CGAL_ImageIO or WITH_CGAL_Qt5 to enable optional components.

4. 4. Build CGAL

After successful configuration, use your chosen build tool (e.g., make on Unix, Visual Studio on Windows) to compile the library. This step can take a significant amount of time depending on your system and the number of enabled components.

5. 5. Install CGAL

Once the build is complete, install CGAL to the directory specified by CMAKE_INSTALL_PREFIX. This typically involves copying headers, libraries, and CMake configuration files to the target location.

cd cgal_source_directory
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX=/usr/local -DWITH_CGAL_ImageIO=ON ../
make -j$(nproc)
make install

Example commands for configuring, building, and installing CGAL on Linux

Troubleshooting Common Issues

Building from source can sometimes present challenges. Here are a few common issues and their solutions:

Missing Dependencies

If CMake reports missing dependencies (e.g., Boost, GMP, MPFR), ensure they are correctly installed and their paths are discoverable by CMake. You might need to set environment variables like BOOST_ROOT or GMP_ROOT.

Compiler Errors

Compiler errors often stem from incompatible compiler versions, missing headers, or incorrect build flags. Verify your compiler version against CGAL's requirements and ensure all necessary development packages for dependencies are installed.

Linker Errors

Linker errors typically indicate that the compiler found the headers but couldn't find the corresponding library files. This could be due to incorrect library paths or missing library installations. Ensure your LD_LIBRARY_PATH (Linux) or PATH (Windows) includes the directories where your dependencies' libraries are located.

# Example of setting Boost root for CMake
export BOOST_ROOT=/path/to/boost/installation
cmake ...

Setting environment variables for CMake