RFR(S) 8074010: followup to 8072383

[David Holmes]

Hi Dean,

On 27/02/2015 3:32 PM, Dean Long wrote:
> This changeset removes references to closed platforms from gcc.make,
> allows $(HS_ALT_MAKE)/linux/makefiles/gcc.make to override the
> default values, and simplifies the logic a bit.  It is targeted for 8u60.

For the benefit of other readers the problem with the existing code is 
that we use platform specific variables to define an additional flag eg:

DEBUG_CFLAGS/amd64 = -g

which is then added to the primary flag variable ie:

DEBUG_CFLAGS += $(DEBUG_CFLAGS/$(BUILDARCH))

That is all good. The problem is the code used to set a default:

    ifeq ($(DEBUG_CFLAGS/$(BUILDARCH)),)
        ifeq ($(USE_CLANG), true)
          # Clang doesn't understand -gstabs
          DEBUG_CFLAGS += -g
        else
          DEBUG_CFLAGS += -gstabs
        endif
    endif

Here we check the current value of $(DEBUG_CFLAGS/$(BUILDARCH)) and use 
it's emptiness to hard-wire a specific flag onto the primary flag 
variable. The problem with that is when we include 
$(HS_ALT_MAKE)/linux/makefiles/gcc.make at the end of the file, it wants 
to set a value of DEBUG_CFLAGS/$(BUILDARCH) for another BUILDARCH and 
consequently the main flags variable will get that value AND the default 
that was hard-wired - and we don't won't that.

However, a cleaner solution that Dean and I have discussed is to simply 
adjust the default-setting as follows:

    ifeq ($(DEBUG_CFLAGS/$(BUILDARCH)),)
        ifeq ($(USE_CLANG), true)
          # Clang doesn't understand -gstabs
          DEBUG_CFLAGS/$(BUILDARCH) = -g
        else
          DEBUG_CFLAGS/$(BUILDARCH) = -gstabs
        endif
    endif

so now if we later set DEBUG_CFLAGS/$(BUILDARCH) for a hitherto unseen 
BUILDARCH it will be expanded in the primary flags variable as expected 
and the "default" will not be used.

Note there's also an existing bug in setting of the FASTDEBUG_CFLAGS 
which has since been fixed in 9 and is now fixed here as well:

-    FASTDEBUG_CFLAGS += $(DEBUG_CFLAGS/$(BUILDARCH))
+    FASTDEBUG_CFLAGS += $(FASTDEBUG_CFLAGS/$(BUILDARCH))

Thanks,
David

> dl
>
> https://bugs.openjdk.java.net/browse/JDK-8074010
> http://cr.openjdk.java.net/~dlong/8074010/8u60.00/
>