#4391: forkIO threads do not properly save/restore the floating point
environment
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Reporter: draconx | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 7.2.1
Component: Runtime System | Version: 6.12.3
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: x86_64 (amd64) | Failure: None/Unknown
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Comment(by simonmar):
Ok, so the simple fact is that if you use functions from `fenv.h` then
floating-point operations are rendered impure, and all bets are off.
We can document exactly what GHC does, so those who really know what
they're doing might be able to use `fenv.h` functions reliably.
Regarding the FFI point: GHC does not preempt a foreign call, so it's safe
to temporarily change the rounding mode during a foreign call, as long as
it is changed back before returing. Both safe and unsafe foreign calls
are fine in this respect.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4391#comment:10>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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