jdk10 build : usage of -fno-var-tracking-assignments g++ flag in hotspot build

[Baesken, Matthias]

Hello,  when building jdk10 on Suse Linux 11 with default gcc/g++  4.3.4 installed, I was running into
compilation errors because of the  missing support for  g++ flag -fno-var-tracking-assignments .

It seems gcc-4.6  has the -fvar-tracking-assignments / -fnovar-tracking-assignments  flags , see

https://gcc.gnu.org/onlinedocs/gcc-4.6.4/gcc/Option-Summary.html#Option-Summary

I have no gcc-4.6 at hand but could verify that gcc-4.7 and gcc-4.8 "know" the flag.
There are various solutions one could do  to avoid  the  compilation error .


1) disallow usage of old gcc versions here :

autoconf/toolchain.m4

TOOLCHAIN_MINIMUM_VERSION_gcc="4.3"

( e.g. change to minimum gcc   4.6 or gcc  4.7  supporting the flags used in the build )


2) remove the flag  -fno-var-tracking-assignments for older gcc versions here :
(in a similar way it was done :  http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/37e693211deb  )

hotspot/make/lib/JvmOverrideFiles.gmk-32-ifeq ($(TOOLCHAIN_TYPE), gcc)
hotspot/make/lib/JvmOverrideFiles.gmk:33:  BUILD_LIBJVM_vmStructs.cpp_CXXFLAGS := -fno-var-tracking-assignments -O0
hotspot/make/lib/JvmOverrideFiles.gmk:34:  BUILD_LIBJVM_jvmciCompilerToVM.cpp_CXXFLAGS := -fno-var-tracking-assignments
hotspot/make/lib/JvmOverrideFiles.gmk-35-endif

What is your preferred solution ?


Thanks, Matthias