ghc-heap-view

Version 0.5 revision 0 uploaded 2013-04-23T08:49:13.000Z by JoachimBreitner.

Package meta

Synopsis

Extract the heap representation of Haskell values and thunks

Description

This library provides functions to introspect the Haskell heap, for example to investigate sharing and lazy evaluation.

It has been inspired by (and taken code from) the vacuum package and the GHCi debugger, but also allows to investiage thunks and other closures.

This package also provides a new GHCi-command, :printHeap, which allows you to inspect the current heap representation of a value, including sharing and cyclic references. To enable the command, you need to load the included ghci script or add it to ~/.ghci, as explained by cabal install. Once it is set up, you can do this:

> let value = "A Value"
> let x = (value, if head value == 'A' then value else "", cycle [True, False])
> :printHeap x
let x1 = _bco
    x21 = []
in (x1,_bco,_bco)
> length (take 100 (show x)) `seq` return () -- evaluate everything
> :printHeap x
let x1 = "A Value"
    x16 = True : False : x16
in (x1,x1,x16)

You can change the maximum recursion depth using :setPrintHeapDepth:

> :setPrintHeapDepth 3
> :printHeap x
let x1 = C# 'A' : ... : ...
in (x1,x1,True : ... : ...)

If the view is impaired by blackholes (written _bh), running System.Mem.performGC usually helps.

The work on this package has been supported by the Deutsche Telekom Stiftung (http://telekom-stiftung.de).

Author

Joachim Breitner, Dennis Felsing

Bug reports

n/a

Category

Debug, GHC

Copyright

2012-2013 Joachim Breitner

Homepage

n/a

Maintainer

Joachim Breitner <mail@joachim-breitner.de>

Package URL

n/a

Stability

n/a

Components

• lib:ghc-heap-view