On 07/08/2014 12:10, Johan Tibell wrote:
Inside GHC we mostly use Int instead of Word, even when we want to represent non-negative values, such as sizes of things or indices into things. This is now causing some grief in https://ghc.haskell.org/trac/ghc/ticket/9416, where an allocation boundary case test fails with a segfault because a n < m Int comparison overflows.
I tried to fix the issue by changing the type of maxInlineAllocSize, which is used on one side of the above comparison, to Word. However, that unravels a bunch of other issues, such as wordsToBytes, ByteOff, etc are all Int-valued quantities.
I could perhaps work around these problems by judicious use of fromIntegral in StgCmmPrim, but I'm a bit unhappy about it because it 1) makes the code uglier and 2) needs to be done in quite a few places.
I think doing the comparison with Integer is the right fix. Relying on Word being big enough for these things is technically wrong because we might be cross-compiling from a smaller word size. Cheers, Simon