other/9682: unclear assembler/linker behaviour

[bas at equator dot com]

>Number:         9682
>Category:       other
>Synopsis:       unclear assembler/linker behaviour
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Feb 13 00:16:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     bas aarts
>Release:        unknown-1.0
>Organization:
>Environment:
bas@marilyn:~/public > gcc --version
gcc (GCC) 3.2.1
Copyright (C) 2002 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

bas@marilyn:~/public > uname -a
Linux marilyn.cam.equator.com 2.4.2-2 #1 Sun Apr 8 20:41:30 EDT 2001 i686 unknown
>Description:
bas@marilyn:~/public > cat attr1.c
int a; extern int h __attribute__ ((alias ("a")));
bas@marilyn:~/public > cat attr2.c
extern int h; int main(void){return h;}
bas@marilyn:~/public > gcc -save-temps attr1.c attr2.c
attr2.o: In function `main':
attr2.o(.text+0x11): undefined reference to `h'
collect2: ld returned 1 exit status

I don't know why I have a missing symbol here

 2 cases:

  1) when in attr1.c, initializing a (so that its not a common anymore),
     it links fine

  2) when in attr1.s, the 
	     .set	h,a
	     .comm	a,4,4

     are interchanged into
	     .comm	a,4,4
	     .set	h,a

     bas@marilyn:~/public > gcc -save-temps attr1.s attr2.c -nostdlib
     /usr/bin/ld: warning: cannot find entry symbol _start; defaulting to 08048074
     bas@marilyn:~/public > nm a.out
     0804908c A __bss_start
     0804908c A _edata
     08049094 A _end
     08049090 B a
     0804908c B h
     08048074 T main

     now a and h are two distinct symbols!
     What is the semantics of the .set directive?
>How-To-Repeat:
see above
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: