RFR JDK-8022407 sun/misc/CopyMemory.java fails with SIGSEGV in Unsafe_SetByte+0x35

[Lois Foltan]

On 8/27/2013 1:29 PM, Christian Thalinger wrote:
> On Aug 27, 2013, at 9:18 AM, Lois Foltan <lois.foltan at oracle.com> wrote:
>
>> Please review the following fix:
>>     open webrev at http://cr.openjdk.java.net/~hseigel/bug_jdk8022407/
>>
>> Bug:
>>     bug link at https://bugs.openjdk.java.net/browse/JDK-8022407
>>
>> Summary of fix:
>>
>> The JDK 8 build on MacOS, when built with the Xcode 4.6.2 clang++ compiler, exhibited a compiler optimization issue when prims/unsafe.cpp was compiled at the default -Os level. As a work around fix, knock the optimization level down down to -O0.
> Why are we lowering to -O0 when you state in the bug report that -O1 also works?  What is the code that breaks?
>
> -- Chris
Hi Chris,
The convention within make/bsd/makefiles/gcc.make indicated that 
historically files that exhibited C++ compiler optimization issues were 
knocked down to /NOOPT or -O0.  I did also check with Coleen to make 
sure that prims/unsafe.cpp was not a performance critical file.  -O1 
does add some optimizations on top of -O0 but not inlining.  I will 
recheck testing with -O1 to confirm and change unsafe.cpp's optimization 
level to -O1 if testing yields good results.

I suspect the optimization problem is in unsafe.cpp's definition of 
Unsafe_GetNativeByte.  I had left off tracking it at that level and 
certainly will not close the JDK bug until I can narrow in further and 
hopefully report to the clang compiler team.

Thanks,
Lois
>> Tests:
>>     MacOS: built fastdebug & product images using clang++ (ran JTREG & vm.quick.testlist)
>>                    built using llvm-g++ to verify prims/unsafe.cpp remained compiled at -Os
>>
>> Thank you,
>> Lois
>>
>>