[GHC] #843: Dependency information for the linking step

[Simon Marlow]

Volker Wysk wrote:
> On Tuesday 08 August 2006 14:08, GHC wrote:
> 
>>#843: Dependency information for the linking step
>>------------------------------------+--------------------------------------
>>- Reporter:  pf1 at volker-wysk.de     |          Owner:
>>      Type:  feature request        |         Status:  new
>>  Priority:  normal                 |      Milestone:
>> Component:  Compiler               |        Version:  6.4.1
>>  Severity:  normal                 |     Resolution:
>>  Keywords:  dependency generation  |             Os:  Linux
>>Difficulty:  Easy (1 hr)            |   Architecture:  Unknown
>>------------------------------------+--------------------------------------
>>- Comment (by simonmar):
>>
>> Then I have another trick for you:
>>
>> {{{
>> ghc --make -pgml echo Main.hs -v0 | ghc -e 'interact (unwords . filter
>> (".o" `Data.List.isSuffixOf`) . words)'
>> }}}
>>
>> Does this solve the problem?
> 
> 
> Yes! I have no idea what's going on, though.

"-pgml echo" uses "echo" as the linker program, so the linker command line is 
sent to stdout, then we pipe it through something that extracts the object 
filenames - I used ghc -e, but you could use sed or perl or something else.  The 
version I gave above doesn't work properly if the filenames contain spaces.

> However, it triggers another problem, which I haven't reported. When 
> calling "ghc -M src/prog.hs", where "prog.hs" is the main module, then the 
> name of the object file is reported as "src/prog.o". When calling it in 
> conjunction with "-odir", such as "ghc -M -odir build src/prog.hs", then you 
> get "build/Main.o". Of course this can't be used, because all of the 
> programs' main modules become "build/Main.o".

This isn't a bug, it's the defined behaviour of -odir.  See the documentation:

http://www.haskell.org/ghc/docs/latest/html/users_guide/separate-compilation.html#output-files

Cheers,
	Simon