Use of STABS debug format

[Andrew Hughes]

Hi all,

It seems that following:

7071904: 4/4 HotSpot: Full Debug Symbols
http://hg.openjdk.java.net/jdk8/jdk8/hotspot/rev/da0999c4b733

a number of architectures on Linux (including x86) have started building with the
STABS debug format rather than DWARF.

This is presumably due to the addition of this block:

+ifneq ($(OBJCOPY),)
+ FASTDEBUG_CFLAGS/ia64 = -g
+ FASTDEBUG_CFLAGS/amd64 = -g
+ FASTDEBUG_CFLAGS/arm = -g
+ FASTDEBUG_CFLAGS/ppc = -g
+ FASTDEBUG_CFLAGS += $(DEBUG_CFLAGS/$(BUILDARCH))
+ ifeq ($(FASTDEBUG_CFLAGS/$(BUILDARCH)),)
+ FASTDEBUG_CFLAGS += -gstabs
+ endif
+
+ OPT_CFLAGS/ia64 = -g
+ OPT_CFLAGS/amd64 = -g
+ OPT_CFLAGS/arm = -g
+ OPT_CFLAGS/ppc = -g
+ OPT_CFLAGS += $(OPT_CFLAGS/$(BUILDARCH))
+ ifeq ($(OPT_CFLAGS/$(BUILDARCH)),)
+ OPT_CFLAGS += -gstabs
+ endif
+endif
+ 

Prior to this, I don't believe product builds had debug information by default.  You'd
have to set DEBUG_BINARIES (something we do).

Is there a reason to use STABS any more?  For our part, it's causing bugs such as:

https://bugzilla.redhat.com/show_bug.cgi?id=841057

This statement:

# Use the stabs format for debugging information (this is the default
# on gcc-2.91). It's good enough, has all the information about line
# numbers and local variables, and libjvm_g.so is only about 16M.
# Change this back to "-g" if you want the most expressive format.

seems dated (Fedora, for example, is on gcc 4.7) and the size argument
seems redundant, given debug information is now stripped and stored in
separate compressed files by default.

Is there any reason to retain the use of STABS on x86 and SPARC, the only supported
architectures not opted out above as far as I can tell?

Note that our concern is the Linux makefile and we're more than happy to leave STABS
in place on Solaris and *BSD, if necessary, as we don't build there :-)
-- 
Andrew :)

Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

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