recompilation check in 6.4

[Simon Marlow]

Hi Serge,

On 05 June 2005 11:58, Serge D. Mechveliani wrote:

> for the first time compiles all the modules before  Foo  in
> 50 seconds.
> Then, I fix an error in  Foo.hs  and repeat  "make dm".
> 
> The  options are set so  that  ghc-6.2.2  gets to  Foo.hs  in less
> than 1 second when doing this repeated `make'.
> It does consider each module before Foo and each time decides that
> there is no need in recompilation. It keeps on going this way:
> --------
> Considering whether compilation is required for Prelude0:
> Skipping  Prelude0  ( ./Prelude0.hs, /foo/source/export/Prelude0.o )
> --------
> and so on, by the scheme
> "Considering ..XX -- {Checking usages .. --} Skipping XX".
> 
> The compiler applies this way:
> --------------------
> /foo/ghc/6.2.2/inst/bin/ghc  -fglasgow-exts
> -fallow-undecidable-instances
> -fallow-overlapping-instances -fno-warn-overlapping-patterns
> -fwarn-unused-binds -fwarn-unused-matches  -fwarn-unused-imports
> -idemotest
> -odir /home/mechvel/dm/1.02/dm/source/export
> -hidir /home/mechvel/dm/1.02/dm/source/export
> -ddump-hi-diffs
> --make DExport  -package-name dm
> --------------------
> 
> Now, when  ghc-6.4  does such a repeated `make', it re-compiles
> all the `previous' modules under the above options:

I'm afraid I don't know what the problem might be.  Probably GHC is
looking in the wrong place for .hi files or .o files, or both.

> ---------
> Chasing modules from: DExport
>     Source file changed or recompilation check turned off
> Compiling Prelude0     ( ./Prelude0.hs, /.../source/export/Prelude0.o
                                         ^^^^^^^
in particul, that looks very strange!  Did you edit that by hand, or is
that the verbatim GHC output?  (copying the verbatim output is usually
better, to avoid confusion).

Cheers,
	Simon