README.md

This repository contains a toy project that demonstrates the build system behavior described in this MongoDB Engineering Journal post.

The project contains three build systems, one written in SCons, one written in CMake, and one written in Meson.

The SCons build is configured so that you can build in three modes:

• Static, with --link-model=static
• Dynamic (the default), with --link-model=dynamic
• Dynamic with ABI driven linking, with --link-model=dynamic-abi

The --link-model=dynamic-abi option will only work if you have the abidw tool from libabigail (not availble for Windows or OS X) installed. If you have it in an unusual location, you can add ABIDW=/path/to/abidw to your SCons invocation to specify where to find it.

The CMake build uses the traditional -DBUILD_SHARED_LIBS technique to decide whether or not to build shared libraries, and defaults to building in dynamic mode.

The Meson build builds in the default way and you can toggle between shared and dynamic linking with the configuration tool: meson configure -Bdefault_library=static/shared. Meson has builtin link skipping based on the Chromium model, it does not support libabigail.

There are three branches in the project:

• master, the baseline configuration
• abi-preserving-change, a mutation over baseline that does not alter the ABI
• abi-altering-change, a mutation over baseline that does alter the ABI.

You can use switching between these branches to follow along with the blog post and observe the rebuild steps associated with the mutations in the various build systems and build system modes.

In particular, it is interesting to compare and contrast the rebuild work when using SCons in --link-model=dynamic mode when introducing both ABI preserving and altering changes, with the rebuild work associated with those same mutations in --link-model=dynamic-abi mode.

If you are aware of other build systems which would exhibit interesting behavior, pull requests to add them are welcome.