space leak in compiler?

[Simon Marlow]

On 07 May 2004 08:11, Serge D. Mechveliani wrote:

> Dear GHC developers,
> 
> I have tested  ghc-6.2.1
>                (installed from (maybe) RPM on RedHat Linux (maybe) 8)
> 
> on my DoCon-2.08 application. It works, mainly.
> 
> But it seems to have a space leak in the compiler.
> 
>                 make space=-M30m docon
>                 (involving  ghc --make ... +RTS -M30m -RTS)
> 
> leads to                        "segmentation fault"
>
> after compling several modules.
> Repeating this command several times allows to build the program.
 
I'm looking into the segmentation fault.  But may I make some
observations/suggestions first:

  - a "space leak" is when a program is using more space than it
    needs to.  You haven't given any evidence that GHC has a space
    leak, only that it uses more space as it compiles modules.  This
    isn't unreasonable.

    Also, it isn't unreasonable for GHC to run out of space during
    --make, but then make more progress when restarted.  It could
    be due to caches built up during compilation, for example.
    
    That's not to say that GHC doesn't have space leaks, just that
    you haven't given us any evidence that it does. (actually I've
    spent quite a bit of time squashing space leaks in GHC, and I know
    that 6.2 does have some small leaks left, but nothing major).

  - If you need to compile on small memory machines, I suggest you
    avoid --make, and use ordinary Makefiles or hmake instead.  Both
    of these will restart the compiler for each module, and hence
    avoid the behaviour you're seeing.  You might even get a speedup,
    because the compiler won't be forced to use the compacting GC
    all the time.

Cheers,
	Simon