#481: Recompilation check fails for TH
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Reporter: simonpj | Owner: simonpj
Type: bug | Status: new
Priority: low | Milestone: _|_
Component: Template Haskell | Version: 6.4.1
Resolution: None | Keywords:
Testcase: TH_recompile | Blockedby:
Difficulty: Unknown | Os: Unknown/Multiple
Blocking: | Architecture: Unknown/Multiple
Failure: Incorrect result at runtime |
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Comment(by JonasDuregard):
Replying to [comment:8 simonmar]:
> I think we should just disable the recompilation check for modules that
use TH or annotations.
I agree. The problem now is that the recompilation checker gives a false
negative, a few false positives is not a big issue in comparison.
Here is an alternative solution, if I have understood the mechanisms
involved correctly:
* We flag modules as one of three three change levels: unchanged,
implementation-changed and interface-changed. This should be simple.
* We mark imports as compile time and/or run time depending on if
imported functions are used in compile time code. I guess this might be a
bit more tricky.
* We recompile if any import is interface-changed or if a compile time
import is implementation-changed.
As a bonus, marking imports is a step towards an optimization which I'm
not sure is currently implemented: if an import is marked TH only, then we
can drop it after evaluating compile time code (this only works if the
generated code does not use functions from the imported module).
I have intended to get hacking on GHC for some time, so maybe looking into
this alternative is a good start.
Jonas
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/481#comment:9>
GHC <http://www.haskell.org/ghc/>
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