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From: gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>)
Newsgroups: net.lang.c
Subject: RE: type cast in initializer
Message-ID: <2137@brl-tgr.ARPA>
Date: Sat, 1-Feb-86 18:41:20 EST
Article-I.D.: brl-tgr.2137
Posted: Sat Feb  1 18:41:20 1986
Date-Received: Mon, 3-Feb-86 05:27:51 EST
References: <2124@brl-tgr.ARPA>
Organization: Ballistic Research Lab
Lines: 32

> > I've found the two lines
> > 
> > 	int	x = 0;
> > 	char	*ptr = (char *) &x;
> > 
> > acceptable to every C compiler I've used, until running into the
> > Whitesmith's C compiler.  They refuse to accept the type coercion "(char *)"
> > on the second initialization.  As I read K&R this should be acceptable
> > through the rules
> 
> The posting did not indicate whether the variables are static or auto.

The variables cannot be static, with those declarations.  I assume you
mean, file scope vs. block scope.  In any case, it doesn't matter; the
example is valid C code.  (However, I wonder what it was trying to do.
Treating the address of an int as a (char *) is rarely required, with
fread/fwrite buffer parameter being the only common occurrence.)

> The initializer should be legal if x is static, but not neccesarily if
> x is declared as an auto.  If x is auto, the compiler could place it in
> a register whose address cannot be taken.

That would be a compiler bug.  Also, the presence or absence of the type
cast would surely be irrelevant in such a case.

> The compiler should be smart enough to notice the address operator and
> disallow register allocation.  K&R only states that variables declared
> register cannot have their address taken.  Anyone know what ANSI says?

"The operand of the unary & operator must be a function locator or an
lvalue that designates an object other than a bit-field or an object
declared with the `register' storage-class specifier."