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From: BAIHELP%TAMSTAR.BITNET@MITVMA.MIT.EDU
Newsgroups: gnu.gcc.bug
Subject: VMS 5.1/GCC 1.35 return value bug (cont.)
Message-ID: <8907201728.AA19125@life.ai.mit.edu>
Date: 20 Jul 89 17:26:00 GMT
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   In reference to the problem of VMS 5.1 needing a longword 1 in r0 if
   no other value is supplied:

       o Unix lets you drop out of the bottom of main.
       o Microsoft C lets you drop out of the bottom of main.
       o From "The C Programming Language" by K&R pg. 26

           A function need not return a value; a RETURN statement
           with no expression causes control, but no useful value,
           to be returned to the caller, as does "falling off the
           end" of a function by reaching the terminating right
           brace.  And the calling function can ignore a value
           returned by a function.
           ... Since MAIN is a function like any other, it may
           return a value to its caller, which is in effect the
           environment in which the program was executed.
           ... we have omitted RETURN statements from our MAIN
           functions up to this point, but we will include them
           hereafter, as a reminder that PROGRAMS SHOULD RETURN
           STATUS TO THEIR ENVIRONMENT.

   Hence, since I won't get into an arguement about "good programming
   style", I will say that the problem lies not with the VAX C compiler
   but with the operating system.  VMS expects a status return value in
   general purpose register 0 and if not supplied retruns an error the
   the process running the program.  Now if "in the interests of good
   style" a programmer would use exit(n); to halt his program on error,
   then sould we not assume that if a program is about to drop off the
   end of main and hasn't set a prefered return value that one may be
   assumed for it.  This allows COMPATIBILITY with the VMS 5.1 operating
   system.

   I am not suggesting this change be made for all implementations of
   GCC, only for those running under VMS which need it.

                                       Bryan A. Ignatow
                                       VMS Software Specialist
                                       Public Domain Software Specialist
                                       Academic Vax Systems
                                       Texas A&M University
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