RFR : 8218136: minor hotspot adjustments for xlclang++ from xlc16 on AIX

[David Holmes]

Hi Matthias,

On 1/02/2019 12:50 am, Baesken, Matthias wrote:
> Please review  this small webrev  . It contains a few changes  for  building hotspot   on AIX with  xlclang++  / xlc16  .
> ( most likely switching to   xlclang++  / xlc16    will be a must once  we introduce C++11/14 features )
> 
> Some comments on the changes :
> 
> 
> - porting_aix.cpp  :  workaround for demangle.h (does not work with xlclang++)

Can't comment as I know nothing about it.

> - arguments.cpp/hpp  :  the UNSUPPORTED_OPTON macro lead  to assigning false to  AllocateHeapAt which is a bad idea (and does not work with xlclang++)

Good catch!

> -   globalDefinitions_xlc.hpp   : xlclang++ sets   __GNUC__ so we must not  have #error ... in this case

Confused. Which other xlc compilers set __GNUC_ as you are changing this 
for all of them? Though to be honest I don't understand this whole 
section anyway - we have a lengthy comment saying why you can't 
necessarily assign NULL to an integer type and to use NULL_WORD instead 
but then it's defined as NULL anyway! I wonder if we used to have some 
other conditions there where it was something different? In any case 
having an if and else that do exactly the same thing seems rather 
pointless to me.

Thanks,
David
> 
> 
> 
> Bug/webrev :
> 
> https://bugs.openjdk.java.net/browse/JDK-8218136
> 
> http://cr.openjdk.java.net/~mbaesken/webrevs/8218136.0/
> 
> 
> Thanks, Matthias
>