OK, I looked a little closer. We need to actually understand this crash, and create a small repro recipe.
It's not at all obvious what the purpose of those methods in Bits.java and Bits.c is - they apparently always byte-swap, but that is very surprising from their names, e.g. copyToIntArray. Give those methods some javadoc! Maybe the crash comes from type punning int* and float* ? We shouldn't suppress the crash unless we can prove it's actually a compiler bug. Why do these methods take Object instead of e.g. int[] as parameters? On Wed, Nov 4, 2015 at 2:12 PM, Martin Buchholz <marti...@google.com> wrote: > At Google, we've also noticed crashes in Bits.c with recent gcc. > Adding nio-dev, since this is not really a build problem. > It appears that Bits.c is resorting to undefined behavior, even though > there is a long tradition of unaligned access on x86 being permitted by the > hardware. > > My colleague Alexander Smundak has also been looking at this, and is > trying to actually fix Bits.c. > > I've also been thinking about this a little. When compiling on x86 with > gcc, we might want to use attribute(aligned(...)) to keep gcc from making > unwarranted assumptions about alignment. > > I think Andrew Haley has also been thinking about efficient array/buffer > operations? > > On Wed, Nov 4, 2015 at 12:56 PM, Brian Burkhalter < > brian.burkhal...@oracle.com> wrote: > >> Please review at your convenience. >> >> Issue: https://bugs.openjdk.java.net/browse/JDK-8140630 >> Patch: Included below >> >> The change is to compile src/java.base/share/native/libjava/Bits.c only >> into libjava.so with normal optimization level (-O2) instead of high >> optimization level (-O3). The other objects in libjava are not affected. >> This is for 64-bit Linux only. With this patch applied, >> java/nio/Buffer/Basic.java now passes on all platforms and there is no >> crash. >> >> Thanks, >> >> Brian >> >> --- a/make/lib/CoreLibraries.gmk >> +++ b/make/lib/CoreLibraries.gmk >> @@ -139,6 +139,12 @@ >> endif >> endif >> >> +ifeq ($(OPENJDK_TARGET_OS), linux) >> + ifeq ($(OPENJDK_TARGET_CPU), x86_64) >> + BUILD_LIBJAVA_Bits.c_CFLAGS := $(C_O_FLAG_NORM) >> + endif >> +endif >> + >> $(eval $(call SetupNativeCompilation,BUILD_LIBJAVA, \ >> LIBRARY := java, \ >> OUTPUT_DIR := $(INSTALL_LIBRARIES_HERE), \ >> >> >
