make/linux/makefiles/vm.make

rev 3024 : 7132779: build-infra merge: Enable ccache to work for most developer builds.
Summary: When a build number is not specified, the JRE_RELEASE_VERSION define contains a date and timestamp. Thus ccache cannot cache the object files for longer than a minute since the define is passed to the compilation of all source files. This change passes JRE_RELEASE_VERSION only to vm_version.cpp and adds a function jre_release_version() to Abstract_VM_Version. This allows all other source files to be ccached.
Reviewed-by: ohair, rottenha
Contributed-by: fredrik.ohrstrom@oracle.com

*** 93,105 ****
    ${INCLUDES}        \
    ${BUILD_VERSION}   \
    ${BUILD_TARGET}    \
    ${BUILD_USER}      \
    ${HS_LIB_ARCH}     \
-   ${JRE_VERSION}     \
    ${VM_DISTRO}
  
  ifndef JAVASE_EMBEDDED
  CFLAGS += -DINCLUDE_TRACE
  endif
  
  # CFLAGS_WARN holds compiler options to suppress/enable warnings.
--- 93,109 ----
    ${INCLUDES}        \
    ${BUILD_VERSION}   \
    ${BUILD_TARGET}    \
    ${BUILD_USER}      \
    ${HS_LIB_ARCH}     \
    ${VM_DISTRO}
  
+ # This is VERY important! The version define must only be supplied to vm_version.o
+ # If not, ccache will not re-use the cache at all, since the version string might contain
+ # a time and date. 
+ vm_version.o: CPPFLAGS += ${JRE_VERSION}
+ 
  ifndef JAVASE_EMBEDDED
  CFLAGS += -DINCLUDE_TRACE
  endif
  
  # CFLAGS_WARN holds compiler options to suppress/enable warnings.