RFR: 8062870: src/share/vm/services/mallocTracker.hpp:64 assert(_count > 0) failed: Negative , counter

[John Rose]

I think on many LP64 platforms the value of (1<<40) is 256, same as (1<<8).  It will seldom be the intended value of (int64_t)1<<40.

The C "<<" operator is notoriously devious (not to say shifty).

For shift/mask arithmetic we should be continuing to use macros from globalDefinitions.hpp.
They are far more reliable than C expressions.

— John

On Nov 10, 2014, at 9:21 AM, Coleen Phillimore <coleen.phillimore at oracle.com> wrote:

> Summary: Signed bitfield size y can only have (1 << y)-1 values.
> 
> We were overflowing the the _pos index and reusing the 0th element in the MallocSiteTable for two different stack traces which caused the assert for deallocation.
> 
> Tested with nsk.quick.testlist and jtreg runtime tests with -XX:NativeMemoryTracking=detail.
> 
> open webrev at http://cr.openjdk.java.net/~coleenp/8062870/
> bug link https://bugs.openjdk.java.net/browse/JDK-8062870
> 
> Thanks,
> Coleen