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[trunk<-vta] Re: [vta, trunk?] ignore .cfi_*-induced .eh_frame compare-debug differences
- From: Alexandre Oliva <aoliva at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Cc: rth at redhat dot com
- Date: Mon, 01 Jun 2009 05:16:16 -0300
- Subject: [trunk<-vta] Re: [vta, trunk?] ignore .cfi_*-induced .eh_frame compare-debug differences
- References: <ork5b2oqkj.fsf@livre.oliva.athome.lsd.ic.unicamp.br>
On Nov 17, 2008, Alexandre Oliva <aoliva@redhat.com> wrote:
> bootstrap-debug is broken in trunk and vta branch on machines that
> support assembler-generated CFI and that don't generate CFI by ABI
> requirements. I got bootstrap-debug failures on at least i686 and
> ppc64, because compilations with -g0 didn't have an .eh_frame section,
> whereas such trivial translation units as ada/final got a simple
> .eh_frame section with -g2, because .cfi_startproc and .cfi_endproc
> are enough to cause the generation of .eh_frame in addition to debug
> info.
> I suppose enabling the assembler to tell whether or not we're
> interested in .eh_frame, in addition to .debug_frame, would be a win
> in terms of stripped binary size, but I wasn't sure it was worth the
> effort. Thoughts?
> In the meantime, I needed some way to ignore these differences, so I
> came up with this patch, that will discard the .eh_frame section from
> one of the object files if the other doesn't have one, and then retry
> the object file compare. This fixed all the boostrap-debug failures I
> had.
> I'm installing this in the branch. Is this enough of a regression fix
> to make it acceptable for the trunk?
Ping?
for contrib/ChangeLog
from Alexandre Oliva <aoliva@redhat.com>
* compare-debug: Don't fail just because of .eh_frame differences.
Index: contrib/compare-debug
===================================================================
--- contrib/compare-debug.orig 2008-11-15 21:13:26.000000000 -0200
+++ contrib/compare-debug 2008-11-15 21:14:11.000000000 -0200
@@ -2,7 +2,7 @@
# Compare stripped copies of two given object files.
-# Copyright (C) 2007 Free Software Foundation
+# Copyright (C) 2007, 2008 Free Software Foundation
# Originally by Alexandre Oliva <aoliva@redhat.com>
# This file is part of GCC.
@@ -67,6 +67,82 @@ if cmp "$1.$suf1" "$2.$suf2"; then
status=0
else
status=1
+
+ # Assembler-generated CFI will add an .eh_frame section for -g not
+ # present in -g0. Try to cope with it by checking that an .eh_frame
+ # section is present in either object file, and then stripping it
+ # off before re-comparing.
+
+ cmd=
+ cmp1=
+ cmp2=
+
+ for t in objdump readelf eu-readelf; do
+ if ($t --help) 2>&1 | grep -e '--\[\?section-\]\?headers' > /dev/null; then
+ cmd=$t
+
+ $cmd --section-headers "$1.$suf1" | grep '\.eh_frame' > /dev/null
+ cmp1=$?
+
+ $cmd --section-headers "$2.$suf2" | grep '\.eh_frame' > /dev/null
+ cmp2=$?
+
+ break
+ fi
+ done
+
+ # If we found .eh_frame in one but not the other, or if we could not
+ # find a command to tell, try to strip off the .eh_frame section
+ # from both.
+ if test "x$cmp1" != "x$cmp2" || test "x$cmd" = "x"; then
+ suf3=$suf1.
+ while test -f "$1.$suf3"; do
+ suf3=$suf3.
+ done
+
+ suf4=$suf2.
+ while test -f "$2.$suf4"; do
+ suf4=$suf4.
+ done
+
+ trap 'rm -f "$1.$suf1" "$2.$suf2" "$1.$suf3" "$2.$suf4"' 0 1 2 15
+
+ if (objcopy -v) 2>&1 | grep -e "--remove-section" > /dev/null; then
+ objcopy --remove-section .eh_frame "$1.$suf1" "$1.$suf3"
+ cmp "$1.$suf1" "$1.$suf3" > /dev/null
+ cmp1=$?
+
+ objcopy --remove-section .eh_frame "$2.$suf2" "$2.$suf4"
+ cmp "$2.$suf2" "$2.$suf4" > /dev/null
+ cmp2=$?
+
+ mv "$1.$suf3" "$1.$suf1"
+ mv "$2.$suf4" "$2.$suf2"
+ elif (strip --help) 2>&1 | grep -e --remove-section > /dev/null; then
+ cp "$1.$suf1" "$1.$suf3"
+ strip --remove-section .eh_frame "$1.$suf3"
+
+ cp "$2.$suf2" "$2.$suf4"
+ strip --remove-section .eh_frame "$2.$suf4"
+
+ cmp "$1.$suf1" "$1.$suf3" > /dev/null
+ cmp1=$?
+
+ cmp "$2.$suf2" "$2.$suf4" > /dev/null
+ cmp2=$?
+
+ mv "$1.$suf3" "$1.$suf1"
+ mv "$2.$suf4" "$2.$suf2"
+ fi
+
+ trap 'rm -f "$1.$suf1" "$2.$suf2"' 0 1 2 15
+ fi
+
+ if test "x$cmp1" != "x$cmp2" && cmp "$1.$suf1" "$2.$suf2"; then
+ status=0
+ else
+ status=1
+ fi
fi
$rm "$1.$suf1" "$2.$suf2"
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Compiler Engineer