RFR: 8149591 - Prepare hotspot for GTest

[Kim Barrett]

> On May 3, 2016, at 3:57 PM, Stefan Karlsson <stefan.karlsson at oracle.com> wrote:
> 
> Hi Kim,
> 
> On 2016-05-03 21:20, Kim Barrett wrote:
>>> 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.
> 
> Yes, that was the purpose.
> 
>>   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.
>> 
> I started with that implementation but got the following error:
> 
> src/share/vm/gc/shared/genCollectedHeap.cpp: In member function 'void GenCollectedHeap::do_collection(bool, bool, size_t, bool, GenCollectedHeap::GenerationType)':
> src/share/vm/gc/shared/genCollectedHeap.cpp:435:44: error: deprecated conversion from string constant to 'va_list {aka char*}' [-Werror=write-strings]
>     FormatBuffer<> gc_string("%s", "Pause ");
> 
> So, adding FormatBufferDummy was a quick-n-dirty solution to fix this.

va_list on this platform seems to be just a typedef for char*.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=33588
which is “won’t fix”.  I hadn’t realized that overloading on va_list isn’t really useful;
I guess that’s why there are lots of “v”-prefixed/suffixed operations around.  I can’t
think of a better solution.  A comment would be nice.