Use of STABS debug format (original) (raw)

Daniel D. Daugherty daniel.daugherty at oracle.com
Tue Jul 31 08:13:30 PDT 2012

On 7/31/12 7:26 AM, Andrew Hughes wrote:

----- Original Message -----

I would love for stabs to go away for linux 32 bit. I think there was a size issue once with that platform and was filling up our disk. I think I changed this recently and noticed that the issue is gone. That's what's noted in the comments. However, there's also a regression here: 1. Prior to 7071904, '-gstabs' was only added for debug builds and fastdebug/opt builds did not have debugging information. 2. After 7071904, '-gstabs' is added to all builds except on arm, ppc, x8664 and ia64. This conflicts with the DEBUGBINARIES option we use for building that adds '-g' to all builds. It means that, with the change in 7071904, our builds now get '-g -gstabs' on x86, whereas before they just got '-g'.

This answers my question about DEBUG_BINARIES. Looks like my changes for 7071904 broke that option.

Maybe the following would work without affecting your builds:

--- a/make/linux/makefiles/gcc.make +++ b/make/linux/makefiles/gcc.make @@ -274,6 +274,8 @@ # DEBUGBINARIES overrides everything, use full -g debug information ifeq ($(DEBUGBINARIES), true) DEBUGCFLAGS = -g + OPTCFLAGS = -g + FASTDEBUGCFLAGS = -g CFLAGS += $(DEBUGCFLAGS) endif The CFLAGS line may be able to be dropped as well.

Actually the CFLAGS line is the only way to be sure that the '-g' gets into all build configs. At one point, there was more than "debug", "fastdebug" and "opt"...

I think the right fix for DEBUG_BINARIES is:

DEBUG_BINARIES overrides everything, use full -g debug information

ifeq ($(DEBUG_BINARIES), true) ! DEBUG_CFLAGS =

I'll file a bug (if there isn't one already) and remove stabs for linux. Thanks :-)

I think we need two bugs here. One for the DEBUG_BINARIES breakage and one for possibly changing to DWARF from STABS on Linux X86.

Dan

Stabs still work better for solaris. We have no plans to change the Solaris build :-)

This still doesn't fix my problem that even the latest version of gdb still can't show or stop in inlined functions on 32 bit (works on 64 bit). Is there a bug for this? It would be nice if this was fixed. I'll leave Andrew Haley (cced) to answer this, as he's much better qualified on this, but I think this may be similar to the problem that made us first notice that the debug format had changed from DWARF to STABS. Thanks, Coleen

On 7/30/2012 7:42 PM, Andrew Hughes wrote: 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 ($(OBJCOPY),) + FASTDEBUGCFLAGS/ia64 = -g + FASTDEBUGCFLAGS/amd64 = -g + FASTDEBUGCFLAGS/arm = -g + FASTDEBUGCFLAGS/ppc = -g + FASTDEBUGCFLAGS += (DEBUGCFLAGS/(DEBUGCFLAGS/(DEBUGCFLAGS/(BUILDARCH)) + ifeq ($(FASTDEBUGCFLAGS/$(BUILDARCH)),) + FASTDEBUGCFLAGS += -gstabs + endif + + OPTCFLAGS/ia64 = -g + OPTCFLAGS/amd64 = -g + OPTCFLAGS/arm = -g + OPTCFLAGS/ppc = -g + OPTCFLAGS += (OPTCFLAGS/(OPTCFLAGS/(OPTCFLAGS/(BUILDARCH)) + ifeq ($(OPTCFLAGS/$(BUILDARCH)),) + OPTCFLAGS += -gstabs + endif +endif + Prior to this, I don't believe product builds had debug information by default. You'd have to set DEBUGBINARIES (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/showbug.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 libjvmg.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 :-) Thanks,

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