ghc-heap-view: Extract the heap representation of Haskell values and thunks

[ bsd3, debug, ghc, library ] [ Propose Tags ]

This library provides functions to introspect the Haskell heap, for example to investigate sharing and lazy evaluation. As this is tied to the internals of the compiler,it only works with specific versions. Currently, GHC 7.4 through 7.10 should be supported.

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).

Versions [faq] 0.1, 0.2, 0.3, 0.3.0.1, 0.3.0.2, 0.3.0.3, 0.3.0.4, 0.4.0.0, 0.4.1.0, 0.4.2.0, 0.5, 0.5.0.1, 0.5.1, 0.5.2, 0.5.3, 0.5.4, 0.5.6, 0.5.7, 0.5.8, 0.5.9, 0.5.10
Dependencies base (>=4.5 && <4.10), binary, bytestring (>=0.10), containers, ghc (<8), template-haskell, transformers [details]
License BSD-3-Clause
Copyright 2012-2014 Joachim Breitner
Author Joachim Breitner, Dennis Felsing
Maintainer Joachim Breitner <mail@joachim-breitner.de>
Revised Revision 1 made by HerbertValerioRiedel at Thu Mar 30 18:33:02 UTC 2017
Category Debug, GHC
Bug tracker https://github.com/nomeata/ghc-heap-view
Source repo head: git clone git://git.nomeata.de/ghc-heap-view.git(Cabal)
Uploaded by JoachimBreitner at Tue Jun 7 11:51:09 UTC 2016
Distributions NixOS:0.5.10
Downloads 10640 total (403 in the last 30 days)
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Status Hackage Matrix CI
Docs not available [build log]
All reported builds failed as of 2016-11-24 [all 3 reports]

Modules

  • GHC
    • GHC.AssertNF
    • GHC.Disassembler
    • GHC.HeapView
      • GHC.HeapView.Debug

Flags

NameDescriptionDefaultType
prim-supports-any

The used GHC supports Any as an argument to foreign prim functions (GHC ticket #5931)

DisabledAutomatic
ghc_7_7EnabledAutomatic
ghc_8_0EnabledAutomatic

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info

Downloads

Note: This package has metadata revisions in the cabal description newer than included in the tarball. To unpack the package including the revisions, use 'cabal get'.

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