RFR: JDK-8238281 Raise minimum gcc version needed to 5.0

[Baesken, Matthias]

Hi Magnus, looks good to me !


> Date: Tue, 4 Feb 2020 22:48:07 +0100
> From: Magnus Ihse Bursie <magnus.ihse.bursie at oracle.com>
> To: build-dev at openjdk.java.net, hotspot-dev
> 	<hotspot-dev at openjdk.java.net>
> Subject: Re: RFR: JDK-8238281 Raise minimum gcc version needed to 5.0
> Message-ID: <ae021fab-faac-b3e5-4d6b-24ef43ca7a49 at oracle.com>
> Content-Type: text/plain; charset=utf-8; format=flowed
> 
> Can I have one more hotspot reviewer, please?
> 
> /Magnus
> 
> On 2020-02-03 09:02, Magnus Ihse Bursie wrote:
> > JEP 347 "Adopt C++14 Language Features in HotSpot" (JDK-8208089) will
> > require that all compilers support the C++14 language extension. The
> > first gcc version to fully support C++14 is 5.0. We need to raise the
> > bar from 4.8 to 5.0.
> >
> > Since removing support for old compilers, especially gcc, can be
> > tricky to handle for some on old and odd setups, I think it's best to
> > do this as a separate step from the C++14 upgrade.
> >
> > On the way, this will allow us to remove some workarounds/close some
> > bugs for really old gcc versions.
> >
> > For hotspot, most notably this means:
> >
> > ?* The workarounds for no ATTRIBUTE_PRINTF are not needed anymore.
> >
> > * The workaround for ATTRIBUTE_ALIGNED is no longer needed.
> >
> > * The workaround in offset_of is not needed anymore. Instead, the
> > appropriate warning is disabled. (In fact, now only xlc need special
> > treatment for offset_of; if that could be fixed now, it would mean
> > that offset_of can be replaced by offsetof in hotspot.)
> >
> > * [Bug fix] The define CAN_USE_NAN_DEFINE (which is used only in
> > share/runtime/sharedRuntimeTrans.cpp), is now always defined for gcc.
> > This was previously done only for gcc >= 4.3 and < 5. I believe this
> > was a bug, and the intention was to allow for old-style NaN behavior
> > in gcc 4.2 and older.
> >
> > Bug: https://bugs.openjdk.java.net/browse/JDK-8238281
> > WebRev:
> > http://cr.openjdk.java.net/~ihse/JDK-8238281-make-gcc-5-
> minimum/webrev.01
> >