ANNOUNCE: MonadCatchIO-foreign

[Simon Marlow]

On 03/06/2010 07:29, Evan Laforge wrote:
> On Sun, May 30, 2010 at 5:15 PM, Antoine Latter<aslatter at gmail.com>  wrote:
>> Hi GHC,
>>
>> Is there a reason that Foreign.Marshall.Array.allocaArray calls into
>> allocaBytes instead of allocaBytesAligned? Since alloca needs the
>> alignment, wouldn't allocaArray also need it?
>>
>> I'm not too up on how memory access is supposed to work, it was just
>> something that jump out at me.
>
> I've been waiting for a response on this, because I'm curious too, in
> fact I always have been.  At the upgrade to 6.10, ghc suddenly started
> using 'alignment' and all my programs which had defined it to
> 'undefined' since I didn't know what alignment was for and it didn't
> seem to be used, started crashing.  So I dug around, dug up the '#let
> alignment' macro boilerplate, and copy and pasted it around.
>
> However, at the same time, my program started rarely but consistently
> crashing with an assertion failure from the gc runtime.  I'm
> suspicious of the inconsistent use of alignment, but it's hard to use
> allocaBytesAligned since it's not exported, and the ffi lib is part of
> ghc and it's not obvious how to modify it.

Here's the ticket:

http://hackage.haskell.org/trac/ghc/ticket/2917

Lennart's patch added allocaBytesAligned to Foreign.Marshal.Alloc, but 
we'll have to do a library proposal to add that.

If you can reproduce the assertion failure, please submit a bug report.

Cheers,
	Simon