target/10806: Illegal instruction calling function in shared object on AIX

target/10806: Illegal instruction calling function in shared object on AIX

[sdowning]

>Number:         10806
>Category:       target
>Synopsis:       Illegal instruction calling function in shared object on AIX
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu May 15 18:06:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     Stuart Downing
>Release:        3.2.2
>Organization:
>Environment:
powerpc-ibm-aix5.1.0.0
>Description:
These modules demonstrate a bug in gcc 3.2.2 on AIX 5.1.

The symptom is an illegal instruction when the foo function is called
when mod.o is converted to a shared object.

I did quite a bit of dividing and conquering from my original code to
get to this result.  I've done some further dividing and conquering
from here to see that the symptom goes away if any of the following
changes are made...

* if static_ptr is not initialized.

* if static_ptr is not static

* if function_static is not static

* if mod.o is not converted to shared (see unshared test)

To demonstrate the symptom run

make

This will build two test programs, one using the non-shared object,
the other using the shared object, then it runs both.

Here's the output from gcc -v for me...
gcc -v
Reading specs from /usr/local/lib/gcc-lib/powerpc-ibm-aix5.1.0.0/3.2.2/specs
Configured with: ../gcc-3.2.2/configure --disable-nls
Thread model: aix
gcc version 3.2.2

(I downloaded a binary gcc distro from http://aixpdslib.seas.ucla.edu)

Note - I didn't gcc -v -save-temps since the test case is self contained.

Feel free to contact me if you need more details

Stuart Downing
FAME Information Services, Inc.
sdowning at fame dot com
>How-To-Repeat:
unzip, untar and make. 
The shared test program will core dump with an illegal instruction.
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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Re: target/10806: Illegal instruction calling function in shared object on AIX

[Stuart F. Downing]

The following reply was made to PR target/10806; it has been noted by GNATS.

From: sdowning@fame.com (Stuart F. Downing)
To: gcc-prs@gcc.gnu.org, gcc-bugs@gcc.gnu.org, gcc-gnats@gcc.gnu.org,
   nobody@gcc.gnu.org
Cc:  
Subject: Re: target/10806: Illegal instruction calling function in shared object on AIX
Date: 16 May 2003 11:19:32 -0400

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10806
 
 I have simplified the test case further.
 Replace mod.c with the following
 
 static char static_thing = 0;
 
 void fun ()
 {
 }
 
 The symptom goes away if 
 
 * the initializer is removed
 * the base type of static_thing is changed to int (but NOT if changed
   to short)
 * the declaration for static_thing is moved after fun
 
 Seems like an alignment problem, but I wasn't able to find any
 switches controlling alignment or initializers to make the symptom go
 away.
 -- 
 Stuart Downing