RFR(T): 8233530: gcc 5.4 build warning -Wc++14-compat after JDK-8233359

[Kim Barrett]

> On Nov 5, 2019, at 2:06 AM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:
> 
> Hi all,
> 
> may I please have reviews for this small build fix:
> 
> Issue: https://bugs.openjdk.java.net/browse/JDK-8233530
> Webrev: http://cr.openjdk.java.net/~stuefe/webrevs/8233530-wc14-compat/webrev.00/webrev/
> Prior discussion: https://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2019-November/036726.html
> 
> Thank you,
> 
> Thomas

The "#ifdef __GNUG__" should not be needed or used.

There are a dozen existing uses of PRAGMA_DIAG_PUSH.

While there aren't currently any other direct uses of
PRAGMA_DISABLE_GCC_WARNING, there are indirect uses via other
PRAGMA_DISABLE_xxx macros.

None of those have __GNUX__ protections (for any X).

> On Nov 5, 2019, at 10:22 AM, Lindenmaier, Goetz <goetz.lindenmaier at sap.com> wrote:
> […] Do we still support gcc 4?
> This change might not be working on gcc 4. PRAGMA_DIAG_PUSH is defined 
> empty for gcc < 4.6.  (I think this does not matter.)

gcc < 4.6 doesn’t matter.

Minimum supported gcc version according to make/autoconf/toolchains.mk is 4.8.
(I’m not sure I actually believe that :)

gcc7.3 is the earliest version listed for jdk13 here:
https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms
(Though there’s no mention here of the BellSoft 32bit linux port, which I possibly
mis-remember as using gcc4.9.)