#3948: unsafeCoerce leaks types
-------------------------------+--------------------------------------------
Reporter: ksf | Owner:
Type: bug | Status: new
Priority: normal | Component: Template Haskell
Version: 6.12.1 | Keywords:
Os: Linux | Testcase:
Architecture: x86_64 (amd64) | Failure: None/Unknown
-------------------------------+--------------------------------------------
Forgive the cryptic summary, here's the code:
{{{
import Unsafe.Coerce
import Foreign
import Data.Bits
foo = (unsafeCoerce (0.50094324::Float))::Int32
bar = (unsafeCoerce (0.30295494::Float))::Int32
main = print (foo, foo .&. 0xffffffff)
>> print (bar, bar .&. 0xffffffff)
}}}
giving the output
{{{
% runhaskell bug.hs
(1056980433,1056980433)
(140502315506921,140502315506921)
}}}
{{{
*Main> :t bar
bar :: Int32
*Main> bar
140549560147177
}}}
where the too-big number changes from run to run, presumably because it
has a different type-tag on each invocation. It does seem to include the
correct data in the low 32 bits, though.
I couldn't replicate this with compiled code, but both GHCi and TH exhibit
this behaviour.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3948>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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