#4321: Unexpected stack overflow prevented by superfluous type annotation
---------------------------+------------------------------------------------
Reporter: bjpop | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.13
Resolution: | Keywords:
Testcase: T4321 | Blockedby:
Difficulty: | Os: Unknown/Multiple
Blocking: | Architecture: Unknown/Multiple
Failure: None/Unknown |
---------------------------+------------------------------------------------
Description changed by igloo:
Old description:
> GHC versions affected:
> 6.13.20100915
> 6.13.20090922
> 6.12.1
> 6.10.4
>
> OS versions tested:
> OS X Snow Leopard
> Ubuntu Linux 9.10 - Karmic Koala
>
> Description:
>
> The attached program computes Pi by integrating 4/(1+x*x) between 0 and
> 1.
>
> The important line of code is this one:
>
> h * (sum (map area [1..n]))
>
> If you compile the program as it is, with this command:
>
> ghc --make -O2 Pi.hs
>
> it runs out of stack space when run like so:
>
> ./Pi 1000000
>
> Stack space overflow: current size 8388608 bytes.
> Use `+RTS -Ksize -RTS' to increase it.
>
> For GHC versions 6.10.4, 6.12.1 and 6.13.20090922
> However, if you add what appears to be a superfluous type annotation to
> the line of code, like so:
>
> h * ((sum (map area [1..n])) :: Double)
>
> The program runs to completion with no stack overflow:
>
> ./Pi 1000000
> 3.1415926535897643
>
> Indeed it works just fine for even larger inputs.
>
> However version 6.13.20100915 overflows the stack regardless of whether
> the type annotation is present or not.
>
> I don't think the type annotation should make any difference to the
> generated code because GHC should infer that the annotated expression is
> of type Double anyway (if you put an erroneous type in the same place,
> GHC complains that it should be a Double).
New description:
GHC versions affected:
* 6.13.20100915
* 6.13.20090922
* 6.12.1
* 6.10.4
OS versions tested:
* OS X Snow Leopard
* Ubuntu Linux 9.10 - Karmic Koala
Description:
The attached program computes Pi by integrating 4/(1+x*x) between 0 and 1.
The important line of code is this one:
{{{
h * (sum (map area [1..n]))
}}}
If you compile the program as it is, with this command:
{{{
ghc --make -O2 Pi.hs
}}}
it runs out of stack space when run like so:
{{{
./Pi 1000000
Stack space overflow: current size 8388608 bytes.
Use `+RTS -Ksize -RTS' to increase it.
}}}
For GHC versions 6.10.4, 6.12.1 and 6.13.20090922
However, if you add what appears to be a superfluous type annotation to
the line of code, like so:
{{{
h * ((sum (map area [1..n])) :: Double)
}}}
The program runs to completion with no stack overflow:
{{{
./Pi 1000000
3.1415926535897643
}}}
Indeed it works just fine for even larger inputs.
However version 6.13.20100915 overflows the stack regardless of whether
the type annotation is present or not.
I don't think the type annotation should make any difference to the
generated code because GHC should infer that the annotated expression is
of type Double anyway (if you put an erroneous type in the same place, GHC
complains that it should be a Double).
--
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4321#comment:13>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
