How to reduce binary footprint when using Haskell package 'plugins'?

Question

I have implemented a simple-minded loader for haskell plugins to my Main.hs module. The only function I use right now is load from this site

Looking at my compiled application size shows me an over 53 MB executable on the x86 architecture. I understand that big parts of GHC are linked in (due to the haskell-source-to-binary-plugin feature) but this is overkill for my purposes.

Is there an officially sanctioned way to shave off the extra features and only keep (dyn-)load?

Answer 1

Depends on the meaning of 'officially sanctioned'. plugins (formerly known as hs-plugins) was designed to be an all-encompassing solution, with code generation and dynamic loading features. It does not aim at minimality.

A less complex package is available under the name direct-plugins, which focuses on the dynamic loading of plugins. This package reads Haskell interface (.hi) files to obtain the actual types of symbols, so that type-safeness is possible, but an unsafe variant is also provided. Unfortunately direct-plugins is bitrotten and does not work (a.t.m.) with GHC v7.6.

At the lowest end of the spectrum there is the unix package which provides a dlopen/dlsym-like mechanism to get hold of symbols that are exported from shared libraries. A convenience layer is also provided to automatically close open libraries after processing with them has terminated. However the symbols are obtained as FFI Ptrs and are not Haskell-callable.

By searching the internet I discovered an abandoned package that seems to be operating at middle ground:

• loading of symbols with Haskell calling convention is provided
• dependencies and package/module hierarchy can be declared
• dependency environment is managed in a thread-safe way.

The original package is authored by Hampus Ram. I have only prepared it for the latest released GHC and did some very shallow testing. Here is the repository:

https://github.com/ggreif/dynamic-loader

The only missing part is type-safe symbol access (by a possibly configurable mechanism). Comments and patches welcome.