The leaky package

[ Tags: bsd3, program, testing ] [ Propose Tags ]

Robust space leak, and its strictification, for testing deepseq-bounded and seqaid.

See also the project homepage for more information.

Please share your comments on this reddit discussion.

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Change log changelog.txt
Dependencies base (==4.*), cpphs (>1.14), deepseq-bounded (>=0.8 && <1.0), deepseq-generics (==0.1.*), generics-sop (==0.1.*), random (==1.1), seqaid (==0.4.0.*), template-haskell [details]
License BSD3
Author Andrew G. Seniuk
Maintainer Andrew Seniuk <>
Category Testing
Home page
Bug tracker
Uploaded Wed Feb 4 15:20:09 UTC 2015 by AndrewSeniuk
Distributions NixOS:
Executables leaky
Downloads 2273 total (19 in the last 30 days)
Rating 0.0 (0 ratings) [clear rating]
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Status Docs not available [build log]
Last success reported on 2015-05-20 [all 8 reports]
Hackage Matrix CI


Note to those reading on Hackage:
Please ignore these flags, which would be better presented in a collapsed state. The flags are mostly for development purposes.

Only when True, provide the options to enable the seqaid preprocessor and GHC plugin.


Blanket seqaid harness at subexpressions of all possible types. Shouldn't need a Cabal flag for this, but it's the same problem of casing over integer values for a macro (in a .cabal file). So this need not be orthogonal to FORCING_STRATEGY, but this way it is ... which is okay, actually. (Can then test interactions with other FS=0..6.)


Finally crumbed and availed myself of -F -pgmF, although only for things which are fairly safe via regex (injecting imports, top-level splices, "deriving instance" statements, LANGUAGE pragmas, etc.). (Later: You can't really do without this anymore, although with FORCING_STRATEGY=4 it is possible.)


Dump periodic stats lines, for FORCING_STRATEGY that need it.


Temporary for testing... (Later: Sadly this is not so temporary. There is some kind of interference between SOP.TH and Seqaid.TH splices which is still unresolved. So, types needing NFDataP (etc.) instances will need to live in a module which is not being harnessed.)


Enable profiling


The problem with using a growing list is, it itself is a leak (as it were), so it's hard to see you've plugged anything. However, the slowdown of "force" relative to "forcep" will be noticed! Alternative to GROWING is FIXED (is at length 10000 at the moment). Fixed list is infinite if INFINITE set below. (INFINITE has no effect when GROWING set.)


XXX For some reason, memory is being retained when REDUCTION is enabled. (Later: Is this still the case? I see it's been set to True throughout development...).


To show DeepSeq.force (FORCING_STRATEGY=1) at its worst.


Put some weighty strict subtrees in the test data structure, so can showcase forcep's specificity relative to forcen.


The original intention was to make this a non-manual flag, to allow the build system to try cpphs first, and if that fails, then to try system-wide cpp (typically GNU). Due to path problems, when the build client installs cpphs in the course of installing, it turns out to be better to use a shell script to delegate which cpp runs, jimmy options, etc.


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


Maintainer's Corner

For package maintainers and hackage trustees

Readme for leaky-

[back to package description]

This leaky mini-project provides a Haskell program exhibiting classic
space leak behaviour.  It leaks in GHC 7.8.3 (and lower), even when
compiled -O2.

  leaky-min-cppd.hs  - a tiny Haskell program that leaks in GHC 7.8.3 -O2
  leaky-min.hs       - like leaky-min-cppd.hs, with some alternatives
  leaky.hs           - a similar but elaborated example, with .cabal flags

In addition to the source files, more information can be found
at the project homepage,
including discussion links (cafe, reddit, etc.).

There may also be a community-editable version at the wiki page.

Configure and build in place:

 >  cabal get leaky                     # download and unpack leaky
 >  cd leaky-                    # (or whatever version it is)
 >  cabal configure && cabal build      # build in place

Run by supplying a seed for the random number generator:

 >  ./dist/build/leaky/leaky 234

Or you may prefer to build in a sandbox:

 >  cabal get leaky
 >  cd leaky-
 >  cabal sandbox init
 >  cabal install --only-dependencies
 >  cabal install

And to run:

 >  ./.cabal-sandbox/bin/leaky 234

NOTE: If you don't build with Cabal, you will need to
put options from leaky.cabal into your command line.

Anyway, seqaid uses both the Cabal library and
the cabal executable, meaning that only FORCING_STRATEGY
from 0 through 3 (refer to leaky.cabal) can work
wtihout the presence of the leaky.cabal file.

The output is explained at
or in the corresponding local document ./HTML/output.html.

The FORCING_STRATEGY CPP macro currently controls the leak and plug
variants, which are best set by editing the leaky.cabal file,reconfiguring
and rebuilding (or reinstalling in the case of a sandbox).  See the
included file rough-fs-twiddling-guide.txt for more details.

There are also some constants in leaky.hs you may like to adjust.

If you have a version of the compiler that does not leak for
the default variant of leaky, please let me know at,
or on the reddit discussion:

It's nice to share your thoughts.

Sept. 20, 2014 / Dec. 2014
Andrew Seniuk
rasfar on #haskell