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Bugzilla Bug 977
  ld test weak fails on cygwin Last modified: 2009-06-08 21:27:52
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Bug#: 977   Hardware:   Reporter: Christian Joensson <christian.joensson@gmail.com>
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Status: VERIFIED   Priority:  
Resolution: FIXED   Severity:  
Assigned To: Dave Korn <dave.korn.cygwin@gmail.com>   Target Milestone:  
Summary:
Keywords:

Attachment Description Type Created Actions
example.tar.bz2 Testcases, object files generated with vendor tools, patch. application/octet-stream 2009-05-24 15:42 Edit None
examples.txt Examination of absolute (non-pc-relative) relocs against weak syms in MS and GNU text/plain; format=flowed 2009-05-24 19:19 Edit None
example-pcrel.tar.bz2 More testcases, object files generated with vendor tools, patch. application/octet-stream 2009-05-29 03:36 Edit None
examples-pcrel.txt Examination of pc-relative relocs against weak syms in MS and GNU text/plain 2009-05-29 03:40 Edit None
Create a New Attachment (proposed patch, testcase, etc.) View All

Bug 977 depends on: Show dependency tree
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Leave as VERIFIED FIXED
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Description:   Last confirmed: 0000-00-00 00:00 Opened: 2005-05-29 11:24 
Windows XP/SP2 cygwin on pentium4 single i686:

binutils             20050520-1     OK
bison                20030307-1     OK
cygwin               1.5.17-1       OK
dejagnu              20021217-2     OK
expect               20030128-1     OK
gcc                  3.3.3-3        OK
make                 3.80-1         OK
tcltk                20030901-1     OK

LAST_UPDATED: Sun May 29 10:40:29 UTC 2005

Native configuration is i686-pc-cygwin

Running /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak.exp ...
/usr/local/src/trunk/objdir-binutils32/ld/../gas/as-new   -o 
tmpdir/weak1.o /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak1.s
/usr/local/src/trunk/objdir-binutils32/ld/../gas/as-new   -o 
tmpdir/weak2.o /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak2.s
/usr/local/src/trunk/objdir-binutils32/ld/ld-new  -o tmpdir/weak --image-base 
0 -T /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak.t tmpdir/weak1.o 
tmpdir/weak2.o
/usr/local/src/trunk/objdir-binutils32/ld/../binutils/objdump -s tmpdir/weak

tmpdir/weak:     file format pei-i386

Contents of section .text:
 1000 08100000 18200000 12121212 34343434  ..... ......4444
Contents of section .data:
 2000 10100000 0c200000 56565656 78787878  ..... ..VVVVxxxx
FAIL: weak symbols
testcase /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak.exp completed 
in 0 seconds

------- Additional Comment #1 From Christian Joensson 2006-05-03 17:06 ------- 
ping... still there:

Running /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak.exp ...
/usr/local/src/trunk/objdir-binutils/ld/../gas/as-new   -o tmpdir/weak1.o
/usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak1.s
/usr/local/src/trunk/objdir-binutils/ld/../gas/as-new   -o tmpdir/weak2.o
/usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak2.s
/usr/local/src/trunk/objdir-binutils/ld/ld-new  -o tmpdir/weak --image-base 0 -T
/usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak.t tmpdir/weak1.o
tmpdir/weak2.o
/usr/local/src/trunk/objdir-binutils/ld/../binutils/objdump -s tmpdir/weak

tmpdir/weak:     file format pei-i386

Contents of section .text:
 1000 08100000 18200000 12121212 34343434  ..... ......4444
Contents of section .data:
 2000 10100000 0c200000 56565656 78787878  ..... ..VVVVxxxx
FAIL: weak symbols
testcase /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak.exp completed in
2 seconds


This is with 

Windows XP Pro/SP2 cygwin Pentium M processor 2.13GHz system with packages:

binutils             20050610-1     2.16.91 20050610
bison                2.1-1          2.1
cygwin               1.5.19-4       
dejagnu              20021217-2     1.4.2.x
expect               20030128-1     5.26
gcc                  3.4.4-1        
gmp                  4.1.4-2        
make                 3.80-1         OK
tcltk                20030901-1     8.4

LAST_UPDATED: Wed May  3 16:45:38 UTC 2006

Native configuration is i686-pc-cygwin

------- Additional Comment #2 From Christian Joensson 2006-06-26 12:15 ------- 
still there... as of 2006-06-24

------- Additional Comment #3 From Dave Korn 2009-03-18 04:27 ------- 
Blimey!  Hello Christian, I've just been catching up on the various Cygwin
binutils failures and reached this one.  Detailed analysis going on now in the
thread on the binutils list at 
    http://sourceware.org/ml/binutils/2009-03/threads.html#00314
and more to come.

------- Additional Comment #4 From Vincent Rivière 2009-03-18 21:55 ------- 
This bug may be related the the already fixed Bug #3041 about weak symbols on 
a.out targets.

------- Additional Comment #5 From Dave Korn 2009-03-19 01:51 ------- 
(In reply to comment #4)
> This bug may be related the the already fixed Bug #3041 about weak symbols on 
> a.out targets.

  Ah, thanks for the pointer!  It looks like we're ok on point #1 (the reloc
against a weak symbol being converted to an offset from the section base symbol,
that's not happening on x86/PE) and I'm half-way through recreating your patch
#3 (In md_apply_fix(): Always put zero values into frags referencing a weak symbol).

>There is still a bug when the reference to the weak symbol contains an offset.
>With my previous patch, the offset is unconditionnaly set to 0.

  Heh, you ran up into the problem that I am anticipating finding next!

  Thanks a lot Vincent, you seem to have discovered and solved the exact same
problem on m68k and your patches will be very useful for me :)

------- Additional Comment #6 From Christian Joensson 2009-03-23 12:24 ------- 
Still there, I guess:

testcase /usr/local/src/trunk/src/ld/testsuite/ld-scripts/sizeof.exp completed 
in 3 seconds
Running /usr/local/src/trunk/src/ld/testsuite/ld-scripts/sort.exp ...
testcase /usr/local/src/trunk/src/ld/testsuite/ld-scripts/sort.exp completed 
in 0 seconds
Running /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak.exp ...
/usr/local/src/trunk/objdir-binutils/ld/../gas/as-new   -o 
tmpdir/weak1.o /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak1.s
Executing on host: sh -c {/usr/local/src/trunk/objdir-binutils/ld/../gas/as-
new   -o tmpdir/weak1.o /usr/local/src/trunk/src/ld/testsuite/ld-
scripts/weak1.s 2>&1}  /dev/null ld.tmp (timeout = 300)
spawn [open ...]
/usr/local/src/trunk/objdir-binutils/ld/../gas/as-new   -o 
tmpdir/weak2.o /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak2.s
Executing on host: sh -c {/usr/local/src/trunk/objdir-binutils/ld/../gas/as-
new   -o tmpdir/weak2.o /usr/local/src/trunk/src/ld/testsuite/ld-
scripts/weak2.s 2>&1}  /dev/null ld.tmp (timeout = 300)
spawn [open ...]
/usr/local/src/trunk/objdir-binutils/ld/ld-new  -o tmpdir/weak --image-base 0 -
T /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak.t tmpdir/weak1.o 
tmpdir/weak2.o
Executing on host: sh -c {/usr/local/src/trunk/objdir-binutils/ld/ld-new  -o 
tmpdir/weak --image-base 0 -T /usr/local/src/trunk/src/ld/testsuite/ld-
scripts/weak.t tmpdir/weak1.o tmpdir/weak2.o 2>&1}  /dev/null ld.tmp (timeout 
= 300)
spawn [open ...]
/usr/local/src/trunk/objdir-binutils/ld/../binutils/objdump -s tmpdir/weak
Executing on host: sh -c {/usr/local/src/trunk/objdir-
binutils/ld/../binutils/objdump -s tmpdir/weak 2>&1}  /dev/null ld.tmp 
(timeout = 300)
spawn [open ...]

tmpdir/weak:     file format pei-i386

Contents of section .text:
 1000 08100000 18200000 12121212 34343434  ..... ......4444
Contents of section .data:
 2000 10100000 0c200000 56565656 78787878  ..... ..VVVVxxxx

tmpdir/weak:     file format pei-i386

Contents of section .text:
 1000 08100000 18200000 12121212 34343434  ..... ......4444
Contents of section .data:
 2000 10100000 0c200000 56565656 78787878  ..... ..VVVVxxxx

tmpdir/weak:     file format pei-i386

Contents of section .text:
 1000 08100000 18200000 12121212 34343434  ..... ......4444
Contents of section .data:
 2000 10100000 0c200000 56565656 78787878  ..... ..VVVVxxxx
FAIL: weak symbols
testcase /usr/local/src/trunk/src/ld/testsuite/ld-scripts/weak.exp completed 
in 4 seconds

This was on 

Windows XP Pro/SP3 cygwin Pentium M processor 2.13GHz system with packages:

binutils             20080624-2     2.18.50.20080625
bison                2.3-1          2.3
cygwin               1.5.25-15      
dejagnu              20021217-2     1.4.2.x
expect               20030128-1     5.26
gcc-ada              3.4.4-999      
gcc-core             3.4.4-999      
gcc-g++              3.4.4-999      
gmp                  4.2.4-1        
libgmp-devel         4.2.4-1        
libmpfr-devel        2.4.1-1        
make                 3.81-2         
mpfr                 2.4.1-1        
tcltk                20080420-1     8.4
w32api               3.13-1         

LAST_UPDATED: daily snapshot 2009-03-23: 2.19.51.20090323

------- Additional Comment #7 From Dave Korn 2009-03-23 13:20 ------- 
(In reply to comment #6)
> Still there, I guess:

  Yep, there was a big thread about it at 
http://sourceware.org/ml/binutils/2009-03/threads.html#00314

I'm drawing up a plan to support ELF-style weaks without breaking mingw-msvc
linkage.

------- Additional Comment #8 From Christian Joensson 2009-05-05 12:11 ------- 
I notice a few checkins that I suspect might be related to eventually resolve
this PR... Dave, what is the status on this work?

------- Additional Comment #9 From Dave Korn 2009-05-05 12:18 ------- 
Crude proto-patch unsuitable for submission posted at
http://sourceware.org/ml/binutils/2009-04/msg00133.html along with rationale for
a design that implements non-MS-compatible C_WEAKEXT symbols.  Dropped it on the
floor a little since then to look at libgcj dll problems, want to get back to it
soon.  (Have been having second thoughts about whether I might just be able to
make it work with compatible C_NT_WEAK symbols after all).

Sorry for the lack of movement, there'll be more soon.

------- Additional Comment #10 From Dave Korn 2009-05-24 15:42 ------- 
Created an attachment (id=3962)
Testcases, object files generated with vendor tools, patch.

I have been analysing how the vendor tools work in order to verify our weak
externals implementation against MS' tools behaviour.  Here are some tests and
specimen object files; I will enter some analysis of what I have found out in
comments in the PR shortly.

See README.txt for description of archive contents.

------- Additional Comment #11 From Dave Korn 2009-05-24 19:19 ------- 
Created an attachment (id=3963)
Examination of absolute (non-pc-relative) relocs against weak syms in MS and
GNU

  At 16kB, this detailed examination is probably a bit long to post in a
comment, so I am attaching it.	The executive summary:

-----------------------------------------------------------------------------
My conclusion from this is that GAS' behaviour is currently incorrect w.r.t the
generation of MS-style weak externals, and should be adapted to match the
behaviour of MASM.  This change alone will resolve the testcase and PR977, and
by all appearances should be more correct and interoperable than the current
situation.
-----------------------------------------------------------------------------

and to prove it I've made the assembler and linker match what the MS tools do:

-----------------------------------------------------------------------------
MS tools:
Contents of section .data:
 401000 28104000 0c104000 56565656 78787878  (.@...@.VVVVxxxx
 401010 2b1d4000 0d1c4000 35134000 0d1f4000  +.@...@.5.@...@.
 401020 28104000 0c104000 12121212 34343434  (.@...@.....4444
 401030 35134000 0d1f4000 2b1d4000 0d1c4000  5.@...@.+.@...@.

Unpatched binutils:
Contents of section .text:
 401000 30104000 0c104000 56565656 78787878  0.@...@.VVVVxxxx
	^^
 401010 331d4000 0d1c4000 3d134000 0d1f4000  3.@...@.=.@...@.
	^^		  ^^
 401020 28104000 18104000 12121212 34343434  (.@...@.....4444
		 ^^
 401030 35134000 191f4000 2b1d4000 191c4000  5.@...@.+.@...@.
		 ^^		   ^^
With the patch included in the previous attachment (examples.tar.bz2):

Contents of section .text:
 401000 28104000 0c104000 56565656 78787878  (.@...@.VVVVxxxx
 401010 2b1d4000 0d1c4000 35134000 0d1f4000  +.@...@.5.@...@.
 401020 28104000 0c104000 12121212 34343434  (.@...@.....4444
 401030 35134000 0d1f4000 2b1d4000 0d1c4000  5.@...@.+.@...@.
-----------------------------------------------------------------------------

Full details inside.  More to follow re: pc-relative relocs.

------- Additional Comment #12 From Dave Korn 2009-05-29 03:36 ------- 
Created an attachment (id=3973)
More testcases, object files generated with vendor tools, patch.

------- Additional Comment #13 From Dave Korn 2009-05-29 03:40 ------- 
Created an attachment (id=3974)
Examination of pc-relative relocs against weak syms in MS and GNU


  Again, it turns out we need to clear the inplace reloc field to generate
correct and interoperable object files to work with MS tools.  Once we do that,
we can get byte-for-byte identical final linked executables:

-----------------------------------------------------
$ objdump -s j34.patched.x j34.ms.x

j34.patched.x:	   file format pei-i386

Contents of section .text:
 401000 e9360000 00ff250f 10400056 56565678  .6....%..@.VVVVx
 401010 787878e9 260d0000 ff25101c 4000e925  xxx.&....%..@..%
 401020 030000ff 25101f40 00000000 00000000  ....%..@........
 401030 ff253b10 4000e9d4 ffffff12 12121234  .%;.@..........4
 401040 343434ff 25481340 00e9c20e 0000ff25  444.%H.@.......%
 401050 3e1d4000 e9b70b00 00000000 00000000  >.@.............

j34.ms.x:     file format pei-i386

Contents of section .data:
 401000 e9360000 00ff250f 10400056 56565678  .6....%..@.VVVVx
 401010 787878e9 260d0000 ff25101c 4000e925  xxx.&....%..@..%
 401020 030000ff 25101f40 00000000 00000000  ....%..@........
 401030 ff253b10 4000e9d4 ffffff12 12121234  .%;.@..........4
 401040 343434ff 25481340 00e9c20e 0000ff25  444.%H.@.......%
 401050 3e1d4000 e9b70b00 00		     >.@......
-----------------------------------------------------

So, I think I know what we need to do now, and a patch to the list will follow.

------- Additional Comment #14 From cvs-commit@gcc.gnu.org 2009-06-08 16:06 ------- 
Subject: Bug 977

CVSROOT:	/cvs/src
Module name:	src
Changes by:	davek@sourceware.org	2009-06-08 16:06:24

Modified files:
	gas/config     : tc-i386.c 
	gas            : ChangeLog 

Log message:
	PR gas/977
	* config/tc-i386.c (md_estimate_size_before_relax):  Don't relax
	branches to weak symbols.
	(md_apply_fix):  Don't convert fixes against weak symbols to
	section-relative offsets, but save addend for later reloc emission.
	(tc_gen_reloc):  When emitting reloc against weak symbol, adjust
	addend to pre-compensate for bfd_install_relocation.

Patches:
http://sources.redhat.com/cgi-bin/cvsweb.cgi/src/gas/config/tc-i386.c.diff?cvsroot=src&r1=1.375&r2=1.376
http://sources.redhat.com/cgi-bin/cvsweb.cgi/src/gas/ChangeLog.diff?cvsroot=src&r1=1.3820&r2=1.3821

------- Additional Comment #15 From Dave Korn 2009-06-08 16:07 ------- 
:-)  Christian, please verify.  (Well, you have already I guess!)

------- Additional Comment #16 From Christian Joensson 2009-06-08 18:54 ------- 
Confirmed to resolve test suite failure.

See http://sourceware.org/ml/binutils/2009-06/msg00148.html

------- Additional Comment #17 From Christian Joensson 2009-06-08 19:01 ------- 
bah, wrong test suite run above... I used my local variant with Korn's patch
already in, this time, I used the pure cvs checkout.

See http://sourceware.org/ml/binutils/2009-06/msg00149.html

------- Additional Comment #18 From Dave Korn 2009-06-08 21:27 ------- 
Technically the bug reporter should be the one to set the "verified" flag, but
you clearly confirmed it was verified, so I'll do it.  Thanks for testing!
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