Xref: utzoo comp.lang.c:35151 comp.std.c:4111
Newsgroups: comp.lang.c,comp.std.c
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: (void *) to function pointer
Message-ID: <1991Jan11.174923.7250@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <1991Jan9.000809.9152@brolga.cc.uq.oz.au> <1037@mwtech.UUCP>
Date: Fri, 11 Jan 1991 17:49:23 GMT

In article <1037@mwtech.UUCP> martin@mwtech.UUCP (Martin Weitzel) writes:
>A less portable solution to transfer a function pointer to a `void *'
>is an intermediate cast to an `int'. The ANSI standard allows such
>casts...

Yes and no.  The wording of the standard implies, but does not quite
state explicitly, that there is *some size* of integer that is big enough
to hold a pointer.  There is no promise that `int' suffices; it might
have to be `long', or even some nonstandardness like `long long'.

Note also that the standard does not promise that you can convert a
pointer to an integer (one that is big enough to hold it) and back
and get a useful pointer.  The description of pointer-integer conversions
is full of "implementation-defined" and "undefined" and makes very few
promises.
-- 
If the Space Shuttle was the answer,   | Henry Spencer at U of Toronto Zoology
what was the question?                 |  henry@zoo.toronto.edu   utzoo!henry