Ah, sneaky. That code is fine because it uses unsafeCoerce# on "memcpy",
changing memcpy from whatever type it is, into
MutableByteArray# s# -> MutableByteArray# s# -> Int# -> s# -> (# s#, () #)
So as long as the GC understands MutableByteArray# it's safe; it's relying
on the C calling convention being handled properly.
On 8/21/07, Bulat Ziganshin
Hello Stefan,
Tuesday, August 21, 2007, 10:08:59 AM, you wrote:
Your code is broken in a most evil and insidious way.
and this code, too? :)
freezeSTUArray :: Ix i => STUArray s i e -> ST s (UArray i e) freezeSTUArray (STUArray l u marr#) = ST $ \s1# -> case sizeofMutableByteArray# marr# of { n# -> case newByteArray# n# s1# of { (# s2#, marr'# #) -> case unsafeCoerce# memcpy marr'# marr# n# s2# of { (# s3#, () #) -> case unsafeFreezeByteArray# marr'# s3# of { (# s4#, arr# #) -> (# s4#, UArray l u arr# #) }}}}
Unreproducable bugs are rarely reported, but they do add to people's impression of how unstable a language/library is.
-- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com