Opened 3 years ago

Last modified 23 months ago

#12506 new bug

Compile time regression in GHC 8. — at Version 5

Reported by: deech Owned by: bgamari
Priority: high Milestone: 8.4.1
Component: Compiler Version: 8.0.1
Keywords: Cc:
Operating System: Unknown/Multiple Architecture: Unknown/Multiple
Type of failure: Compile-time performance bug Test Case:
Blocked By: Blocking:
Related Tickets: Differential Rev(s):
Wiki Page:

Description (last modified by deech)

This bug is entirely reproducible but unfortunately takes some setup. I don't have a minimal example.

The regression is happening in FLTKHS (, the Haskell bindings to the FLTK( toolkit, and in particular to this GUI ( In GHC 7.8, it taks 5-9 seconds to compile and link in 7.10.3, that goes up to 12-15 seconds and finally in GHC 8 it shoots up to 45 seconds. While these numbers come from my i7, 16GB RAM Linux laptop, the compile time regression is proportionally reproducible across machines and operating systems.

Here are the steps to reproduce it

  • Install FLTK Please follow the instructions here ( but only the first set which is about installing FLTK 1.3.
  • Clone the repo with the offending application: git clone
  • Build the application and reproduce the problem:
    • cabal install fltkhs
    • cabal install c2hs
    • At the root of the repo do cabal build fltkhs-fluid-tree

Change History (5)

comment:1 Changed 3 years ago by deech

Description: modified (diff)

comment:2 Changed 3 years ago by simonpj

Type of failure: None/UnknownCompile-time performance bug

comment:3 Changed 3 years ago by bgamari

Owner: set to bgamari
Priority: normalhigh

I'll be adding this one to my queue. Thanks deech.

comment:4 Changed 3 years ago by deech

Description: modified (diff)

comment:5 Changed 3 years ago by deech

Description: modified (diff)
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