RFR: 8074319: barrier_set_cast defined via friend injection

[Volker Simonis]

On Tue, Mar 3, 2015 at 8:52 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
> On Mar 3, 2015, at 12:55 PM, Volker Simonis <volker.simonis at gmail.com> wrote:
>>
>> I was looking at the same problem today because it also fails on AIX
>> with xlC 12.1.
>>
>> I'm not one hundred percent sure but I currently more tend to say it
>> is a compiler bug although I'll have to dive deeper into the C++
>> standard before I can give a qualified answer here.
>
> The relevant standardese, from C++03 7.3.1.2, is
>
>   If a <tt>friend</tt> declaration in a non-local class first declares
>   a class or function (footnote 83: this implies that the name of the
>   class or function is unqualified) the friend class or function is a
>   member of the innermost enclosing namespace.  The name of the friend
>   is not found by simple name lookup until a matching declaration is
>   provided in that namespace scope (either before or after the class
>   declaration granting friendship).
>

Thanks for providing the reference. That makes it pretty clear.

>> But your change looks good and it also works on AIX. So if you like,
>> you can consider it reviewed.
>
> Thanks.
>
>> However, with your change "barrier_set_cast()" won't be an inline
>> function any more which may have performance impacts (this is
>> something you'll have to judge).
>
> The definition moved to namespace scope in the webrev I posted is
> declared inline.
>

Sorry, I've overlooked that. That makes your change even better :)

Thanks again for fixing,
Volker


>> I'd like to propose a similar change which keeps "barrier_set_cast()"
>> as inline function and still works with Xcode5 and xlC 12 on AIX:
>>
>> diff -r 71f4ed3c627f src/share/vm/memory/barrierSet.hpp
>> --- a/src/share/vm/memory/barrierSet.hpp        Tue Mar 03 13:25:23 2015 +0000
>> +++ b/src/share/vm/memory/barrierSet.hpp        Tue Mar 03 18:51:47 2015 +0100
>> @@ -32,6 +32,10 @@
>> // This class provides the interface between a barrier implementation and
>> // the rest of the system.
>>
>> +class BarrierSet;
>> +template<typename T>
>> +T* barrier_set_cast(BarrierSet* bs);
>> +
>> class BarrierSet: public CHeapObj<mtGC> {
>>   friend class VMStructs;
>> public:
>
> This doesn’t have an inline storage class specifier.
>
>> PS: I'm a little bit confused that this error hasn't been catched by
>> JPRT because the OpenJDK Wiki
>> (https://wiki.openjdk.java.net/display/Build/Supported+build+platforms)
>> lists clang 5.1 as official build platform for MacOS X?
>
> Maybe the JPRT farm is still lagging?
>