Usage of C++ features

[Lindenmaier, Goetz]

Hi,

Thanks a lot for all the feedback!  To summarize, there is nothing in 
the pipe besides the exceptions in the compiler, but the desire to
use new features/stl once compiler issues are resolved.

> I have this lingering feeling that we shouldn't need to use template template 
> parameters for the binaryTreeDictionary code but I haven't experimented with
Yes Mikael, you are right.  You don't need them.
I would appreciate a lot if the following webrev would be 
considered as contribution to jdk9 and jdk8u20.
http://cr.openjdk.java.net/~goetz/webrevs/rm_tmptmp_param/

If I don't get any objections I'll open a bug and mail a proper
RFR?

I compiled it on linuxx86_64 with gcc 4.3.4 and 4.8, and on sparcv9 with SS12u1.
I tested dbg, fdbg and opt builds. I did some simple tests.  Tonight the change
will run with all our tests on the ppc port, build on windows and sparc included.

Best regards,
  Goetz.




-----Original Message-----
From: Mikael Gerdin [mailto:mikael.gerdin at oracle.com] 
Sent: Donnerstag, 6. Februar 2014 12:56
To: hotspot-dev at openjdk.java.net
Cc: David Holmes; Lindenmaier, Goetz
Subject: Re: Usage of C++ features

On Thursday 06 February 2014 21.27.51 David Holmes wrote:
> Hi Goetz,
> 
> On 6/02/2014 8:33 PM, Lindenmaier, Goetz wrote:
> > Hi,
> > 
> > wrt. our (SAPs) various ports which are running on old machines, built
> > with old compilers for compatibility, I would like to find out about
> > the OpenJDK policy regarding 'real' C++ features.
> 
> I don't think there is such a thing as "OpenJDK policy" for this. Things
> need to be evaluated on their merits taking into account a range of
> factors, including compiler compatibility issues.
> 
> > Recently, we found increasing usage of C++ features.
> > 
> > -          'throw()'  in nmethod operator new
> 
> > -          usage of namespace std::
> AFAICS only std::nothrow is in use, which combines with the use of
> throw() in numerous (most?) operator new definitions to make it clear
> that these don't throw any exceptions.
> 
> That said the compiler folk have expressed interest in using C++
> exceptions within the compiler.
> 
> > -          template template parameters in binaryTreeDictionary.hpp|cpp
> 
> Can't comment on that.

I have this lingering feeling that we shouldn't need to use template template 
parameters for the binaryTreeDictionary code but I haven't experimented with 
it.
I'd prefer to simplify that just for the sake of sanity.

/Mikael

> 
> > We would like to know whether you are planning to increase the
> > usage of C++ or even use C++11 features.  Or, whether you are planning
> > to keep the policy to avoid C++ features that caused problems to
> > compilers in the past.
> 
> I can envisage usage of C++11 atomics at some point. But it depends on
> it being supported across sufficient compilers. What else is coming in
> C++11?
> 
> I think everything has to be considered on a case-by-case basis. You
> presumably have some things in mind ?
> 
> Just my 2c. I'm not a policy maker. :)
> 
> Cheers,
> David
> 
> > Best regards,
> > 
> >    Goetz.