Newsgroups: comp.lang.c Path: utzoo!henry From: henry@zoo.toronto.edu (Henry Spencer) Subject: Re: Whither _noalias_? Message-ID: <1991Feb7.050917.24550@zoo.toronto.edu> Organization: U of Toronto Zoology References: Date: Thu, 7 Feb 1991 05:09:17 GMT In article enag@ifi.uio.no (Erik Naggum) writes: >I haven't seen any mention of "noalias" in ANSI C compilers I've >talked to, so I just wonder if I wasn't alone in not really grasping >what noalias was good for and why its introduction was required. Its purpose was to let the programmer tell the compiler that arguments to a function were not aliases for each other, for the sake of optimization on vector machines and the like. The optimizing people really cared about it. Unfortunately, (a) the description was exceedingly cryptic and repeated efforts failed to produce one that "did the right thing", (b) it spread slimy tentacles everywhere in the standard libraries, and (c) it was introduced far too late in the development of the standard. The result was a firestorm of protest, including a declaration of war :-) from Dennis Ritchie and formal threats to vote against ratification of ANSI C as ISO C. The committee backed down and removed it. You really need to get a copy of the final standard; drafts that old are not reliable references. -- "Maybe we should tell the truth?" | Henry Spencer at U of Toronto Zoology "Surely we aren't that desperate yet." | henry@zoo.toronto.edu utzoo!henry