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[Bug gas/10193] New: gas produces different .o files with the same input


From: chenyang dot cq at gmail dot com
Subject: [Bug gas/10193] New: gas produces different .o files with the same input .s file and cmd line arguments on enfs
Date: 23 May 2009 13:49:58 -0000

I found a very strange problem of "as" when I was building gcc-4.3.3.
I got a "Bootstrap comparison failure!", when means that some .o files
 were not identical between stage2 and stage3. However, it turns out that
the problem was introduced by "as" not gcc itself. For some .s files, "as"
will produce a different .o file each time it is invoked with the same .s file:

> as  -V -Qy -o obj1.o testtree.s
GNU assembler version 2.19 (x86_64-unknown-linux-gnu) using BFD
version (GNU Binutils) 2.19
> as  -V -Qy -o obj2.o testtree.s
GNU assembler version 2.19 (x86_64-unknown-linux-gnu) using BFD
version (GNU Binutils) 2.19
> ll obj*.o
-rw-r--r--  1 tester users 87360 2009-05-21 20:37 obj1.o
-rw-r--r--  1 tester users 87360 2009-05-21 20:37 obj2.o
> cmp -i 16 obj1.o obj2.o
obj1.o obj2.o differ: byte 66006, line 132

My system is:
 -Linux gnode2 2.6.5-7.97-smp #1 SMP Fri Jul 2 14:21:59 UTC 2004
x86_64 x86_64 x86_64 GNU/Linux
 -SUSE LINUX Enterprise Server 9 (x86_64)
And the file system is some kind of enfs

I have transferred the testtree.s file to another AMD machine, and saw
no problem there.
I have also copied the static linked binutils binaries on that "no
problem" machine to use
on the "problem" machine. And the problem didn't go away.  In a word,
the same static
linked "as" runs deterministically on one machine,
non-deterministically (produce different
.o files) on another.

I guess that It's a system-specific problem. And it may be hard
to reproduce it on another machine. So both the above mentioned
 testtree.s, obj1.o, obj2.o are attached to help examine the bug.

-- 
           Summary: gas produces different .o files with the same input .s
                    file and cmd line arguments on enfs
           Product: binutils
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gas
        AssignedTo: unassigned at sources dot redhat dot com
        ReportedBy: chenyang dot cq at gmail dot com
                CC: bug-binutils at gnu dot org


http://sourceware.org/bugzilla/show_bug.cgi?id=10193

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