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

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).

Modules

[Last Documentation]

Flags

Automatic Flags

Name	Description	Default
prim-supports-any	The used GHC supports Any as an argument to foreign prim functions (GHC ticket #5931)	Disabled
ghc_7_7		Enabled
ghc_8_0		Enabled

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

Downloads

• ghc-heap-view-0.5.6.tar.gz [browse] (Cabal source package)
• Package description (revised from the package)

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'.

Maintainer's Corner

Package maintainers

• DennisFelsing, JoachimBreitner

For package maintainers and hackage trustees

• edit package information

Candidates

• 0.5.10, 0.5.11, 0.6.0