GHC core plugin supporting the derive-storable package.

The package helps derive-storable package in forcing compile time evaluation of sizes, alignments and offsets.

Introduction

The goal of derive-storable-plugin is to support the derive-storable package. It introduces optimisations to GStorable methods derived using GHC.Generics at core-to-core passes.

Usage

Just add a -fplugin=Foreign.Storable.Generic.Plugin flag and you're set. You might also want to pass a verbosity flag -vX, where X is either 0,1 or 2. By default the verbosity flag is set to -v1.

{-# LANGUAGE DeriveGeneric, DeriveAnyClass #-}
{-# OPTIONS_GHC -fplugin=Foreign.Storable.Generic.Plugin #-}
{-# OPTIONS_GHC -fplugin-opt=Foreign.Storable.Generic.Plugin:-v1 #-} 
module Main where

import GHC.Generics

import Foreign.Storable.Generic
import Foreign.Ptr
import Foreign.Marshal.Alloc

data Point = Point {
    x :: Float,
    y :: Float
    } deriving (Show, Read, Generic, GStorable)

main = do
    let val = Point 0.0 10.0
    ptr <- malloc :: IO (Ptr Point)
    putStrLn "Created a ptr with value of"
    print =<< peek ptr
    poke ptr val
    putStrLn "And now the value of ptr is:"
    print =<< peek ptr

Benchmarks

The plugin was benchmarked using derive-storable-benchmark package. The benchark measures handwritten Storable instances, raw GStorable instances and optimised-by-plugin GStorable instances. The code was compiled with -O1 optimisation flag.