RFC009 - Dynamic linking hell#

2022-11-06, @eliemichel

Current Situation#

An OpenMfx plugin is dynamically loaded into the host’s main process.

Key limitations#

Dynamic linking the same plugin into multiple third party programs has always been a problem. When the plugin itself depends on dynamically linked libraries, the latter may conflict with the host’s symbols.

A very representative example is the one of MfxCascade, a plugin based on the OpenCascade CAD kernel. OpenCascade uses Intel’s TBB, and the Blender host as well. However, they do not link against the same version, hence Blender is not able to load the MfxCascade plugin at runtime.


Option A#

As this issue is often raised in the Visual Effects industry, studios and software vendors came with the VFX Reference Platform, a list of standardize versions of all major libraries linked by VFX software tools.

We can require from the effect that they comply strictly with this reference sheet.


  • This is incompatible with bridging with mesh processing libraries initially meant for other industries, like OpenCascade.

  • The VFX Reference Platform may or may not hold forever.

Option B#

Based on the VFX Reference Platform idea, we can provide for each host a build script, so that it is easy enough for plugin vendors to batch build for all hosts. We could also formalize a mechanism for host vendors to publish such build configs.


  • This may require multiple builds for each OS.

  • This might be hard to maintain.

Option C#

Add the possibility to run problematic plugins in a different process, like the Houdini Engine can do. Data buffers are communicated using shared memory.


  • Plugins can be sandboxed

  • They cannot crash the main process


  • This comes with an overhead because it requires to copy host buffers into the shared memory pages.

  • Writing an host gets more complicated, though this feature would be optional.


  • Around 2019 The issue was met regarding linking the Houdini Engine to Blender. Fortunately the Houdini Engine provides a split process mode to circumvent the issue.

  • Around 2020 The issue is encountered with MfxCascade. This plugin is put on hold.

  • 2022-11-06 Discussions lead to rethinking the problem as being serious enough to need attention.