HEADS UP: bugs in GHC 6.12.2

Simon Marlow marlowsd at gmail.com
Wed May 12 04:41:04 EDT 2010

Hi folks,

I'm sorry to say that in GHC 6.12.2, as a result of fixing a couple of 
bugs in 6.12.1, we (well, I) managed to introduce some more serious ones:


The first causes gtk2hs programs to crash, and we have a report of it 
affecting hmatrix too.  There's no workaround unfortunately: the problem 
is that we changed some data structures related to FFI calls, with the 
result that a nested callback (calling out to C, back to Haskell, out to 
C again and back to Haskell in the same thread) can result in a crash or 
a bogus result.

The second causes lazy bytestring's hGetContents to block waiting for a 
full buffer, when it should just return the data already read.  You can 
work around this by using bytestring- instead of the supplied

We'll put out 6.12.3 with fixes for these as soon as possible.  In the 
meantime, if you are still on 6.12.1 and not encountering any problems, 
I don't recommend upgrading.

Sorry for the inconvenience.


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