Article View: net.lang.c
Article #9179Re: Indirect comma assigned from side effects
From: Chris Torek
Date: Thu, 21 Aug 1986 20:27
Date: Thu, 21 Aug 1986 20:27
33 lines
1539 bytes
1539 bytes
In article <792@navajo.STANFORD.EDU> rokicki@navajo.STANFORD.EDU
(Tomas Rokicki) writes:
>... For example, consider the program:
>
> int lhs, rhs, index; int *pointers[9];
> foo() { *( index=lhs, pointers[index] ) = sideeffects(); }
>
>The question is, does C allow for the possibility that the order
>of evaluation might be "index=lhs" then "sideeffects()" then
>"*pointers[index]=<result>"?
No. The compiler can, however, effectively generate either of the
following:
temp = sideeffects();
index = lhs;
*pointers[index] = temp;
or
index = lhs;
tempp = pointers[index];
*tempp = sideeffects();
>... On the other hand, if C does not allow the compiler to
>generate such code, then the statement is well defined.
Not really, since one sequence sets index=lhs before the call, and
the other after.
--
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1516)
UUCP: seismo!umcp-cs!chris
CSNet: chris@umcp-cs ARPA: chris@mimsy.umd.edu
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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!mnetor!seismo!umcp-cs!chris From: chris@umcp-cs.UUCP (Chris Torek) Newsgroups: net.lang.c Subject: Re: Indirect comma assigned from side effects Message-ID: <3047@umcp-cs.UUCP> Date: Thu, 21-Aug-86 16:27:03 EDT Article-I.D.: umcp-cs.3047 Posted: Thu Aug 21 16:27:03 1986 Date-Received: Thu, 21-Aug-86 22:28:31 EDT References: <792@navajo.STANFORD.EDU> Reply-To: chris@umcp-cs.UUCP (Chris Torek) Organization: University of Maryland, Dept. of Computer Sci. Lines: 33