Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!tut.cis.ohio-state.edu!cs.utexas.edu!sun-barr!decwrl!shelby!csli!keith
From: keith@csli.Stanford.EDU (Keith Nishihara)
Newsgroups: comp.sys.dec
Subject: DS3100 linker problems.
Message-ID: <11579@csli.Stanford.EDU>
Date: 3 Jan 90 18:05:19 GMT
Sender: keith@csli.Stanford.EDU (Keith Nishihara)
Reply-To: Neil Hunt <Neil%teleos.com@ai.sri.com>
Organization: Center for the Study of Language and Information, Stanford U.
Lines: 35

System: DecStation 3100 running Ultrix:
  Ultrix Worksystem V2.0 (Rev. 7) System #1: Mon Jul 31 15:49:08 PDT 1989
  /bin/ld: version 1.31. (strings shows dates from early 87 to 11/88).

With certain sizes of executable objects, the final linking phase introduces
illegal instructions, where the library or object module from which
those intructions were obtained is fine.  Symptom: core dump -- illegal
instruction.  Fix: alter the alignment of instructions on the pages,
by introducing some additional code early in the program: e.g.

#ifdef SPACING
	printf("This is a spacer to move the following instructions forward");
	printf("This is a spacer to move the following instructions forward");
	printf("This is a spacer to move the following instructions forward");
[perhaps 20 or 30 lines total]
	printf("This is a spacer to move the following instructions forward");
#endif

Note that if illegal instructions are observed in the code for a function,
they can be seen before _any_ instructions
have been executed (it is not a random pointer problem), and the relink with
altered alignment generates _different_ instructions for the same function
from the same identical library (the library file is _unchanged_.)


Does anyone have a definitive explanation, or better yet, a new /bin/ld
for 1.31 which works.

Neil/.		Neil%teleos.com@ai.sri.com

P.S. Many programs, including several X clients, and g++ 1.36.2, for example,
have illegal instructions which go away if you add a few printf statements
somewhere before the illegal instructions.  I cannot believe that no one
at DEC has seen this problem.  Nor can I believe a fixed version does not
exist.