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

[Magnus Ihse Bursie]

On 2020-02-05 01:48, Jesper Wilhelmsson wrote:
> Looks good!
Thanks.
> In a few comments you refer to the version with just the number 5. Would it be more correct to write 5.0?
> (doc/building.html and doc/building.md)
I agree, it looks a bit odd. I changed it to 5.0 before pushing.

/Magnus
>
> /Jesper
>
>> On 4 Feb 2020, at 22:48, Magnus Ihse Bursie <magnus.ihse.bursie at oracle.com> wrote:
>>
>> 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
>>>