Possibility of integer overflow in JfrThreadSampler::run()

[Severin Gehwolf]

Hi Yasumasa,

On Wed, 2019-01-09 at 20:27 +0100, Severin Gehwolf wrote:
> Hi,
> 
> On Wed, 2019-01-09 at 13:23 +0900, Yasumasa Suenaga wrote:
> > Hi all,
> > 
> > I posted this issue in May 2018 [1].
> > It still occurs in current jdk/jdk when it was build by GCC 8.
> > 
> > We can avoid it with -fno-strict-overflow GCC option. So I propose to add it
> > to JvmOverrideFiles.gmk:
> > 
> >   http://cr.openjdk.java.net/~ysuenaga/jfr-integer-overflow/webrev.1/
> > 
> > JDK-8147466 has been fixed with similar change for jdk7u [2].
> > 
> > What do you think?
> 
> This fix is masking undefined behavior (signed integer overflow) in
> code. We should fix the code instead. The previous fix looked better,
> but would still overflow if:
> 
> max(_interval_java, 10) + last_java_ms > max_jlong

This fix works for me:
http://cr.openjdk.java.net/~sgehwolf/webrevs/ub-jfr-sampler-fix/webrev/

Feel free to use it.

Thanks,
Severin

> Note that the assertion triggers on a fastdebug build with GCC 8.2 and
> running :jdk_jfr test group for me (18 tests fail). Failures go away
> with -fno-strict-overflow.
> 
> > I will file it to JBS if it is accepted.
> 
> Please file a bug.
> 
> Thanks,
> Severin
> 
> > 
> > Thanks,
> > 
> > Yasumasa
> > 
> > [1] https://mail.openjdk.java.net/pipermail/hotspot-jfr-dev/2018-May/000047.html
> > [2] http://hg.openjdk.java.net/jdk7u/jdk7u/jdk/rev/35dcc0db31dc