NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/std/c/222

Internet Message Format | 1996-08-06 | 3.2 KB

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From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c,comp.std.c
Subject: Re: Integral conversion e.t.c. (was: Re: Hungarian notation)
Date: Mon, 29 Jan 96 23:55:02 GMT
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In article <4eindq$[e-mail]>
           [e-mail] "Peter Seebach" writes:

>I would tend to expect a diagnostic in strict ANSI mode, and would also
>expect a diagnostic for including <sys/stat.h> in strict ANSI mode.  Neither
>is often forthcoming.

ANSI doesn't require a diagnostic for either of those so an implementation
that follows the letter of the standard doesn't have to diagnose either
of them. Your compiler may have an extra feature (i.e. not required by the
standard) where it tries to diagnose code that isn't strictly conforming.
In the general case that's a hopeless task since many forms of system
dependency are not detectable at compile time but you might expect such a
compiler to diagnose the cases above. I have yet to come across a compiler
that attempts to do this however, it probably isn't all that useful
in practice.

>gcc warns only on implementations where they consider it a hosted environment;
>on most systems, they weasel and claim to be a freestanding implementation.

Since gcc is a compiler that doesn't come with a library, in itself it
can't be a hosted implementation. Where it is used with other people's
libraries calling it a hosted implementation implies taking responsibility
for those libraries. I certainly wouldn't be keen on doing that!

>>Normally, I would expect (at the very least) a compiler to generate a
>>warning or an error for a main that it did not support.  In fact,
>>however, my compiler (gcc) accepts the following definition without
>>the slightest complaint, although I'd rather not think about what will
>>happen when I access parameter d:
>
>>       int main( char a , int b , long c , double d )
>
>I think that may actually legitimately require a diagnostic; 5.1.2.2.1 gives
>us a constraint (?) of "If they are defined, the parameters to the main
>function shall obey the following constraints: ..." and some definitions.

Interesting observation. I expect that the constraints referred to in
5.1.1.3 are the constraint sections. This is worth clarifying though.

>I would take this as implying that main *must* conform.  I would like to see
>them go from "can be declared" to "shall be declared".

That makes no difference. Violation of a 'shall' clause results in
undefined behaviour in the same way as a lack of definition. See 3.16
(which I just included in a post prior to this). To require a diagnostic
you would need to create a constraints section.

--
-----------------------------------------
Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
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