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From: karl@haddock.UUCP (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: structure element offsets
Message-ID: <191@haddock.UUCP>
Date: Tue, 9-Dec-86 23:46:59 EST
Article-I.D.: haddock.191
Posted: Tue Dec  9 23:46:59 1986
Date-Received: Wed, 10-Dec-86 12:28:23 EST
References: <1096@spice.cs.cmu.edu> <7377@utzoo.UUCP> <427@viper.UUCP>
Reply-To: karl@haddock.ISC.COM.UUCP (Karl Heuer)
Organization: Interactive Systems, Boston
Lines: 16
Summary: use of malloc is portable

In article <427@viper.UUCP> dave@viper.UUCP (David Messer) writes:
It is
>interesting in that the only thing gaurenteed about casts on pointers is the
>conversion to a long and back and conversion to a pointer to a smaller type
>and back, which also results in the same original pointer value.  One
>interesting thing is, by these rules, the use of malloc(), for anything other
>than char arrays, is non-portable.

No, it isn't.  The *implementation* of malloc() is nonportable, but since it
is guaranteed to return a maximally-aligned "char *" (the result of casting
a widetype pointer, which, as you mentioned, may be safely cast back), its
use is portable.  (Well, I guess if you want to nit-pick, the rules you quoted
don't specifically allow (int *)(char *)(double *)double_aligned_intptr; is
that what you mean?)

Karl W. Z. Heuer (ima!haddock!karl or karl@haddock.isc.com), The Walking Lint