RFR(10)(S): 8181503: Can't compile hotspot with c++11

[Thomas Stüfe]

Hi Gerard, Kim,

On Tue, Jun 13, 2017 at 9:59 PM, Gerard Ziemski <gerard.ziemski at oracle.com>
wrote:

>
> > On Jun 12, 2017, at 5:07 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
> >
> > src/share/vm/utilities/vmError.hpp
> >  38   static uint         _id;              // Solaris/Linux signals: 0
> - SIGRTMAX
> >
> > I think changing the type of _id from int to uint is really not so
> > simple. There's a bit of a type mess in this area, with some functions
> > expecting or using int and others uint. _id is set from an int value.
> > It is passed to os::exception_name, which takes an int argument. The
> > windows implementation of that function immediately casts that
> > argument to a uint, but the posix implementation actually wants an int
> > value. OTOH, there are other places that expect or treat _id as a
> > uint. So the proposed change is really just rearranging the deck
> > chairs in that mess, and is not really much of an improvement.
> > I *think* using uint consistently throughout for this value could be
> > made to work, but I haven't completely worked through it.
>
> Thanks Kim,
>
> I didn’t see anywhere in the code the _id being compared using arithmetic
> (ex: “if (_id < 0)"), so I thought we were good using uint. Thanks for
> taking a closer look.
>
> Would redefining the 3 troublesome enums from:
>
> enum VMErrorType {
>  INTERNAL_ERROR   = 0xe0000000,
>  OOM_MALLOC_ERROR = 0xe0000001,
>  OOM_MMAP_ERROR   = 0xe0000002
> };
>
> to:
>
> enum VMErrorType {
>  INTERNAL_ERROR   = 0xe000000,
>  OOM_MALLOC_ERROR = 0xe000001,
>  OOM_MMAP_ERROR   = 0xe000002
> };
>
> (i.e. removing one 0 from the defined values) be a good fix? SIGRTMAX is
> 64 (on Linux tested using “kill -l") so anything well above that would be
> user defined and therefore safe?
>
>
We did something similar in our (SAPs) port to prevent between VMErrorType
and existing SEH exception numbers. We extended the _id type to uint64_t
and moved the VMErrorType enum values up to the upper 32bit (SEH numbers
are DWORD, so 32bit unsigned). We also visibly changed them to not look in
the debugger like typical SEH exception numbers.

enum VMErrorType {
  INTERNAL_ERROR   = 0xab0000000,
  OOM_MALLOC_ERROR = 0xab0000001,
  OOM_MMAP_ERROR   = 0xab0000002,
}

Code has been running in our VM for many years without issues.

..Thomas



>
> cheers
>
>