Problem linking on Win32

[Jason Dagit]

On 10/9/06, Lemmih <lemmih at gmail.com> wrote:
> On 10/9/06, Jason Dagit <dagit at codersbase.com> wrote:
> > Hello,
> >
> > I have a program and I'd like to permanently change the default RTS
> > options.  According to the GHC manual I can do that by linking with a
> > snippet of C code:
> > http://www.haskell.org/ghc/docs/latest/html/users_guide/runtime-control.html
> >
> > Look at section 4.14.5 at the bottom of the page.
> >
> > I can't seem to get cabal to link my program together so that my
> > custom rts options take affect.  To help demonstrate I've created a
> > minimal test case:
> >
> > ------------- oom.cabal -------------------
> > name: OutOfMemory
> > version: 0.1
> > cabal-version: -any
> > license: AllRightsReserved
> > license-file: ""
> > build-depends: base -any
> > c-sources: rtsoptions.c
> > exposed-modules: Main
> >
> > Executable: oom
> > Main-is: Main.hs
> > ------------- end oom.cabal -----------
> >
> > --------------- Main.hs ---------------------
> > module Main where
> >
> > main :: IO ()
> > main = print $ foldl (+) 0 [1..100000000]
> > --------------- End Main.hs --------------
> >
> > /* rtsoptions.c */
> > char *ghc_rts_opts = "-M1024M -K256M";
> > /* end rtsoptions.c */
> >
> > Also using the standard Setup.lhs:
> > #! /usr/bin/runghc
> >
> > \begin{code}
> > import Distribution.Simple
> > main = defaultMain
> > \end{code}
> >
> > When build and run this I get:
> > C:\projects\tmp>runghc Setup.lhs build
> > Preprocessing library OutOfMemory-0.1...
> > Preprocessing executables for OutOfMemory-0.1...
> > Building OutOfMemory-0.1...
> > [1 of 1] Compiling Main             ( Main.hs, dist\build\oom\oom-tmp/Main.o )
> > Linking dist\build\oom\oom.exe ...
> >
> > C:\projects\tmp>dist\build\oom\oom.exe
> > Heap exhausted;
> > Current maximum heap size is 268435456 bytes (256 Mb);
> > use `+RTS -M<size>' to increase it.
> >
> > On the other hand, if I build rtsoptions.c manually and add it to the
> > ghc-options line in the .cabal file it does build and run until in
> > needs more than 976Mb (showing that the default RTS options are indeed
> > different).
>
> Add the C source to the executable instead of the library. In other
> words, move the 'c-sources' under 'main-is'.

Ah yes.  I feel silly now to have been stumped on this so long.  As
soon as you say it, it makes instant sense since Cabal conceptually
keeps the library stanza separate from executable stanzas.

Perhaps it would help if cabal throw a warning when the first stanza
is not separate from the 'meta data' by a blank line.  So that the
library stanza is always standing by itself too.  Just a thought.

Thanks for the help!
Jason