[OpenJDK 2D-Dev] [PATCH FOR REVIEW] Building ExtensionSubtables.cpp should use -fno-strict-aliasing

[Phil Race]

I suppose the problem that some new version of GCC enables this option 
by default and
we could run into a problem at run time if we don't disable it ?

But this patch would appear to disable it for the whole ICU library .. 
and any other C++ code in the .so
which I would have to suppose impacts the compiler's ability to optimise 
the code, in order to
eliminate a single warning.

Can you devise a more targeted fix ?

-phil.

On 5/23/2012 5:59 AM, Andrew Hughes wrote:
> At present, the building of ExtensionSubtables.cpp produces a warning:
>
> ../../../src/share/native/sun/font/layout/ExtensionSubtables.cpp:57:31:
> warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
>
> due to this code:
>
> // read a 32-bit value that might only be 16-bit-aligned in memory
> #define READ_LONG(code) (le_uint32)((SWAPW(*(le_uint16*)&code)<<  16) + SWAPW(*(((le_uint16*)&code) + 1)))
>
> where code is a le_uint32.
>
> This can be avoided by setting -fno-strict-aliasing, as done in this webrev:
>
> http://cr.openjdk.java.net/~andrew/no-strict-aliasing/
>
> making the code safer in the process.
>
> Ok for jdk8?  If so, can I have a bug ID for this please?
>
> Thanks,