Path: utzoo!mnetor!uunet!mcvax!tuvie!rcvie
From: rcvie@tuvie (ELIN Forsch.z.)
Newsgroups: comp.lang.c
Subject: Re: Some possible deficiencies in dpANS (or whatever its called)
Message-ID: <559@tuvie>
Date: 19 Jan 88 15:10:42 GMT
References: <4755@tut.cis.ohio-state.edu!
Reply-To: rcvie@tuvie.UUCP (Alcatel-ELIN Forsch.z.)
Organization: Technical University of Vienna
Lines: 46
Keywords: none
Summary: It may be perfectly all right!

In article <4755@tut.cis.ohio-state.edu! lvc@tut.cis.ohio-state.edu (Lawrence V. Cipriani) writes:
!I was looking over the Oct '86 draft and noticed a couple of
!things I believe are deficiencies.  If these have been corrected
!then n this posting.
!
!1) In the definition of statement (section 3.6) one of the legal
!forms of statement is the expression and null statement (section
!3.6.3).  The syntax is:
!
!        expression-statement:
!                expression    ;
!			  opt
!
!Looking at the definitions of the various types of expressions
!it looks like the following are valid *statements*:
!
!	i;
!	j << 2;
!	k == 0;
!	"hello world\n";
!
!I believe this is a deficiency.  These statements have no effect
!(other than eating a machine cycle which might be desired I guess),
!and in fact lint flags them.  This is related to the "language
!induced errors" discussion recently.  The programmer probably
!meant to write:
!
!	i++; /* or something similar */
!	j <<= 2;
!	k = 0;
!	p = "hello world\n"; /* or something similar */
!
!If the current draft allows these null effect statements (other
!than the null statement) please consider disallowing them.  Please
!mail me an address to write to so I may raise this objection.
!

C was designed as a system programmer's language! For these people it may
be very important to change the status of a register, flag, or whatever
by evaluating an expression whithout assigning its value anywhere (which
might change the flag, register, ... again). Good compilers, however, will
produce a warning like "Expected side effects" or whatever. But allowing this
syntax is certainly no deficiency.

			Dietmar Weickert,
			ALCATEL-ELIN Research Center, Vienna, Austria.