head aches in parser/Parser.hs
nominolo at googlemail.com
Tue Aug 5 04:30:22 EDT 2008
How is that better than having only the actual source files in you
src directory? All generated files will go into dist-*/ and there's
no way to confuse anything. Cabal does allow including pre-generated
files in dist tarballs, but for development, generated files have
intentionally be moved into dist/.
On 5 Aug 2008, at 06:51, Roman Leshchinskiy wrote:
> On 05/08/2008, at 14:15, Judah Jacobson wrote:
>> It seems that the old, pre-Cabal build system did not clean some or
>> all of the preprocessed files (such as Parser.hs). This was not much
>> of a problem in practice, because the Makefiles used the relative
>> timestamps to tell whether to regenerate Parser.hs from Parser.y. In
>> contrast, Cabal stores all generated files in a separate directory
>> (compiler/dist-stage[1/2]), and thus doesn't need to look at relative
>> timestamps; so it gets confused by the old, leftover Parser.hs et al.
> Ah, thanks for clarifying this. I did remove all the files by hand
> eventually but couldn't figure out why this was necessary.
>> Ironically this is another reason that switching to Cabal is a win --
>> cleaning of preprocessed files happens automatically.
> Can't resist the urge to nitpick... IIUC, where the make-based
> system would generate Parser.hs at most once per build Cabal now
> (unnecessarily) regenerates it for each stage. So it is really
> using a different algorithm with slightly worse performance but
> better cleaning behaviour. It would have been trivial to implement
> with make, too.
> But this has highlighted what is IMO a problem in Cabal's design.
> It doesn't know that to generate the module Parser it needs to
> start with Parser.y and just uses whatever source file it finds. If
> that happens to be Parser.y things work but if it finds something
> else things break. This looks very fragile to me. Could Cabal
> perhaps allow .cabal files to explicitly specify which source files
> to use? As in:
> exposed-modules: Parser(Parser.y)
> Cvs-ghc mailing list
> Cvs-ghc at haskell.org
Push the envelope. Watch it bend.
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