RFR(xs): 8078666: JVM fastdebug build compiled with GCC 5 asserts with "widen increases"

[Severin Gehwolf]

Hi,

Adding hotspot-dev for wider audience. IMHO hotspot should not rely on
undefined behaviour (overflow on signed int/long is undefined) and this
should get fixed.

--Severin

On Mon, 2015-04-27 at 16:18 +0200, Severin Gehwolf wrote:
> Hi,
> 
> Could somebody please review and sponsor the following patch?
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8078666
> Webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8078666/webrev.02/
> 
> We've discovered this issue in Fedora where we were seeing a strange
> memory leak issue of an OpenJDK build with GCC 5. More info in the bug.
> 
> As it turns out, current hotspot relies on undefined behaviour in
> normalize_int_widen()/normalize_long_widen() where an integer overflow
> can occur on some inputs.
> 
> The fix is to do the math on the unsigned type where overflows are well
> defined.
> 
> Thanks,
> Severin
> 
> 
>