RFR(XS) 8087120: [GCC5] java.lang.StackOverflowError on Zero JVM initialization on non x86 platforms

[Severin Gehwolf]

Hi,

Could somebody please review this Zero only change? I'd also need a
sponsor who can push the change for me once reviewed.

Bug: https://bugs.openjdk.java.net/browse/JDK-8087120
webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8087120/webrev.01/

The issue is that Zero relies on undefined behaviour for getting the
current stack pointer by allocating a variable on the stack and
returning its address. With GCC 5 returning an address of a local
variable will always be 0, thus causing the issue. It worked fine with
older GCC versions, because they returned the actual address of the
variable.

The fix is to use GCC's built-in function "__builtin_frame_address".
This also works on GCC 5. It's GCC specific, though. On the other hand,
I don't know if anybody builds Zero without GCC. An alternative would be
to use alloca, but that has strange semantics if the stack pointer
cannot be extended. Thoughts?

Thanks,
Severin