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

[Erik Joelsson]

Looks good to me.

/Erik

On 2020-02-03 00:02, 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
>