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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: C pointer semantics with dynamically allocated struct
Date: Thu, 08 Oct 2015 10:43:42 -0700
Organization: None to speak of
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supercat@casperkitty.com writes:
> On Wednesday, October 7, 2015 at 6:33:18 PM UTC-5, Keith Thompson wrote:
>> Yes.  malloc() is a standard library function, and its behavior is
>> defined by the standard.  The behavior of attempting to modify p[10] is
>> not defined by the standard (though of course an implementation is free
>> to document the behavior if it likes).
>
> If the library documents the behavior of "malloc", "free", etc. in greater
> detail than required by the Standard, and such documentation implies that
> modifying certain bytes immediately outside the allocation will have
> particular effects, would there be any standard means to ensure that a
> compiler would honor the semantics of the library?

No, why would there be?  A conforming implementation is free to document
whatever it likes, and to behave in any way it likes within the rules
set by the standard.  Enforcement of an implementation's non-standard
documentation is outside the scope of the standard.

I suppose a future C standard could add a rule requiring implementations
to conform to their own documentation, but I see no point in doing so.
If an implementation violates its own documentation, it's a bug, and you
can complain to the vendor.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"