Re: Union C++ standard terminology

Derek Jones <>
Wed, 1 Dec 2021 13:35:57 +0000

          From comp.compilers

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From: Derek Jones <>
Newsgroups: comp.compilers
Date: Wed, 1 Dec 2021 13:35:57 +0000
Organization: Compilers Central
References: 21-11-004 21-11-008 21-11-009 21-11-010 21-11-011 21-11-013 21-11-015 21-11-016
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Keywords: C, standards
Posted-Date: 05 Dec 2021 13:29:09 EST
In-Reply-To: 21-11-016
Content-Language: en-US


>> The Conformance section specifies how "shall" and "shall not" are to be
>> interpreted.
> But it does NOT define "will" and "will not", and "must" and "must
> not", and "does" and "does not" ... terms which are used liberally in
> the documents, apparently without having any normative definition.

The ISO directives say:
'Do not use "must" as an alternative for "shall".'
Although the IETF treats the terms similarly:

My recollection is the the ISO directives used to strongly recommend
against the use of any form of "must".

The get out of jail answer is to point out that
"ISO/IEC 2382−1:1993, Information technology — Vocabulary — Part 1:
Fundamental terms"
appears in the list of Normative references.
Back when libraries used to contain paper documents, I spent an
afternoon rummaging around the various parts of ISO 2382.
I was surprised to find out how few terms are defined and how
vague/general the definitions actually were.

I have been in committee meetings were people said the term was
defined in ISO 2382, we found out that it wasn't, then everybody
switched to saying: "Ok, common usage English applies" (whatever
that is; the "Longman Grammar of Spoken and Written English" is
great, but out of print, see the student edition).

There is one occurrence of the word "must" in the standard, in an

"does not" is common, mostly in examples and footnotes.
The instances I have looked at look reasonable, e.g.,
"Each ? that does not begin one of the trigraphs..."

The three instances of "will not" all appear in footnotes.

> Not to mention that the Conformance section generally is not included
> in draft documents. Nor are there easy to find, freely available,
> references on how to read various standards documents.

It appears in every copy of the draft standard I have seen.

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