RFR: JDK-8211071: unpack.cpp fails to compile with statement has no effect [-Werror=unused-value]

[Magnus Ihse Bursie]

> 25 sep. 2018 kl. 10:21 skrev Roman Kennke <rkennke at redhat.com>:
> 
> Not sure this is the correct list. Please redirect as appropriate.

I believe core-libs is the appropriate place. Cc:d. 

> 
> Please review the following proposed change:
> 
> 
> There are 3 asserts in unpack.cpp which check only constants, and which
> the compiler rejects as 'has no effect' (in fastdebug builds). This
> seems to be caused by:
> 
> https://bugs.openjdk.java.net/browse/JDK-8211029
> 
> I propose to fix this by defining a STATIC_ASSERT which can evaluate and
> reject this at compile time:
> 
> Webrev:
> http://cr.openjdk.java.net/~rkennke/JDK-8211071/webrev.00/

From a build perspective, this looks good. But please let someone from core-libs review also. 

> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8211071
> 
> It might be useful to define the STATIC_ASSERT in a more central place
> to be used elsewhere too. For example, there is a similar #define in
> Hotspot's debug.hpp

Unfortunately, we do not have a good place to share definitions like this across JDK libraries. :-( The need for that has struck me more than once. For some stuff, we mis-use jni.h. But it would definitely be out of line to add a STATIC_ASSERT there. 

/Magnus

> 
> Thanks, Roman
>