Status of building problem with GCC 6

[Kim Barrett]

> On Jul 1, 2016, at 10:17 AM, Yasumasa Suenaga <yasuenag at gmail.com> wrote:
> For HotSpot, I think JDK-8156980 should be fixed at first.
> I've proposed changes as below:
> 
> -----------
> diff -r ba08710f3b6c make/lib/CompileJvm.gmk
> --- a/make/lib/CompileJvm.gmk   Mon Jun 27 09:35:18 2016 +0200
> +++ b/make/lib/CompileJvm.gmk   Tue Jun 28 12:10:09 2016 +0900
> @@ -187,6 +187,11 @@
> 
>  JVM_OPTIMIZATION ?= HIGHEST_JVM
> 
> +JVM_CXXFLAGS := $(JVM_CFLAGS)
> +ifeq ($(TOOLCHAIN_TYPE), gcc)
> +  JVM_CXXFLAGS += -std=gnu++98 -fno-delete-null-pointer-checks -fno-lifetime-dse
> +endif
> +
>  ################################################################################
>  # Now set up the actual compilation of the main hotspot native library
> 
> @@ -202,6 +207,7 @@
>      CFLAGS := $(JVM_CFLAGS), \
>      CFLAGS_DEBUG_SYMBOLS := $(JVM_CFLAGS_SYMBOLS), \
>      CXXFLAGS_DEBUG_SYMBOLS := $(JVM_CFLAGS_SYMBOLS), \
> +    CXXFLAGS := $(JVM_CXXFLAGS), \
>      vm_version.cpp_CXXFLAGS := $(CFLAGS_VM_VERSION), \
>      DISABLED_WARNINGS_clang := delete-non-virtual-dtor dynamic-class-memaccess \
>          empty-body format logical-op-parentheses parentheses \
> —————

Please keep in mind that my understanding of the new build system is
pretty weak.  That said, this doesn't look to me like the right way to
fix JDK-8156980.

There is already code that is supposed to deal with both the -std
option and the additional code generation options, which seems to work
for some of the packages that we build, but is not affecting the
Hotspot build for some reason.  Adding a completely separate way to
deal with this just for Hotspot seems contrary to the unification
effort that was part of the new build system.

-fno-lifetime-dse is a relatively recent option, and needs to be
conditionalized.  And discussion during the review of JDK-8151841 led
to the additional code generation options being limited to gcc6+.
The existing code mentioned above is conditionalizing that way, except
it's just not working for Hotspot.