Linking Against a Static Version of LibXml2 with CMake

Learn how to configure your CMake build system to link against a static version of `LibXml2`, eliminating the need for DLLs and ensuring a single-binary deployment.
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Linking Against a Static Version of LibXml2 with CMake: A Comprehensive Guide

In today's development landscape, the need for streamlined, efficient application deployment is crucial. When modernizing a CMake build system, developers often face the challenge of linking dependencies like LibXml2 statically, to achieve a single binary outcome. If you find yourself in this predicament, you're in the right place! This guide will walk you through the steps necessary to link against a static version of LibXml2 without relying on DLLs.

The Problem: Dynamic Linking with CMake

When you're switching to static compilation for all dependencies in your project, the last thing you want is to accidentally link against a shared DLL. However, many developers find that the default behavior of the FindLibXml2 module in CMake picks up the relocatable shared DLL instead of the static library. This poses a significant problem!

Scenario Example

Imagine you have compiled LibXml2 with the following command:

[[See Video to Reveal this Text or Code Snippet]]

This command generates both the DLL (libxml2.dll) and the static library files (libxml2.lib and libxml2_a.lib). When configuring your CMake project with:

[[See Video to Reveal this Text or Code Snippet]]

CMake may link against the dynamic library by default. So the burning question remains - how can you ensure you're linking statically?

The Solution: Custom Configuration with CMake

To solve this issue effectively, follow these organized steps:

Step 1: Set CACHED Variables Correctly

A crucial tip is to set the cached variable before calling the find module. It ensures that CMake recognizes which library you intend to use. Here’s how you can approach this:

Step 2: Find the Static Library

Instead of relying solely on find_package, you can use find_library to locate the static library explicitly. This method allows you to specify the exact library you want while accommodating both debug and release builds without hardcoding paths.

Here's an example CMake configuration:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

CMAKE_PREFIX_PATH: Specifies the path to the directory containing the library installations. This is essential for finding the correct library files.

find_library: This command searches for the static version of LibXml2 specifically. By setting NAMES libxml2_a, you are explicitly telling CMake to look for the static library.

message(STATUS ...): Outputs a message to the console about the found library, which helps in troubleshooting.

set(LIBXML2_LIBRARY ...): This sets your library variable to the path of the found static library.

Conclusion

By following these steps, you can effectively configure your CMake project to link against a static version of LibXml2. With this setup, you’ll no longer have to worry about unintentionally linking to a dynamic library, ensuring that your application can be deployed as a single binary without external DLL dependencies.

Now that you have a clear understanding, it's time to modernize your build system and enjoy the benefits of static linking for your applications!

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