RFR: 8149591 - Prepare hotspot for GTest

[Kim Barrett]

> On Apr 29, 2016, at 9:47 PM, Igor Ignatyev <igor.ignatyev at oracle.com> wrote:
> 
> Hi,
> 
> I’d like to renew this RFR.
> 
> besides updated previous changes, new webrev contains two new things:
> - new vm-flag — ExecutingUnitTests, we use it in debug jvm to print a clean error message (w/o assert, line, file, etc). it is needed to simplify comparing error message in “death” tests (the tests which intentionally cause crashes/asserts)
> - if CreateCoredumpOnCrash is false, we don't determine default core path
> 
> webrev: http://cr.openjdk.java.net/~iignatyev/8149591/webrev.00/
> JBS: https://bugs.openjdk.java.net/browse/JDK-8149591
> 
> Thanks,
> — Igor

Not a full review yet, but a question before I go on.

I don’t understand the purpose of FormatBufferDummy.  I’m guessing it is to disambiguate the new
FormatBuffer constructor taking a va_list argument.  But with these two overloads:

  FormatBuffer(const char* format, …);
  FormatBuffer(const char* format, va_list ap);

the latter should always be a better match when the second argument is a va_list, and should never
be a match at all otherwise.  (An overload containing ellipsis is always the least good match.)  So I
think we shouldn’t need FormatBufferDummy.