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From: info-vax@ucbvax.ARPA
Newsgroups: fa.info-vax
Subject: Re: Possible VAX/VMS PL/I bug
Message-ID: <4837@ucbvax.ARPA>
Date: Thu, 14-Feb-85 18:29:10 EST
Article-I.D.: ucbvax.4837
Posted: Thu Feb 14 18:29:10 1985
Date-Received: Fri, 15-Feb-85 06:10:11 EST
Sender: daemon@ucbvax.ARPA
Organization: University of California at Berkeley
Lines: 27

From: Roger Hale <roger@ll-sst>

From: lionel%eludom.DEC@decwrl.ARPA  (Steve Lionel)
> The message gives you a warning.  A warning only means that the compiler
> detected something you may not have intended (an implicit conversion),
> not that the program is incorrect.   Referencing an un-initialized variable
> is also perfectly proper PL/I but you would like to have to compiler warn
> you that you have done this if it can.
> 
> The way to eliminate such warnings is to use the /NOWARN qualifier on the
> command line.
> 
I have seen this suggested several times as a `fix' for this problem
(excessive/spurious warnings), and I feel about the same way towards it
as toward the suggestion not to run lint on one's C programs.
If the compiler is doing its job right, its warnings should be about things
worth worrying about, and I should want to hear them.  If they are warnings
about things that `clearly can't happen' -- if I can't convince a good
compiler of that, why I am writing my code this way?

In the case in question, with multiple entries forcing multiple exits
on each return, flow analysis ought to show which entries can't reach
which returns.  The VAX PL/I compiler does this sort of analysis for
other purposes, doesn't it?

Roger Hale
roger@ll-sst[.arpa]