Rationale for allowing const T* = T* wanted.

[Chris Torek]

In article <3913 at lupine.NCD.COM> rfg at lupine.ncd.com (Ron Guilmette) writes:
>I have been stirring up trouble in x3j16 [regarding const]

Good :-)

In my opinion, the entire const/non-const setup in ANSI C is wrong.
(I am not entirely happy with it in C++ either, but note that the notion
of `const' is fairly different in the two languages.)

There is something fundamentally `bad' about the fact that, for instance,
a strchr() function must cast a const-pointer to a non-const pointer:

	char *strchr(const char *str, int c0) {
		char c = c0, sc;
		for (; *str != c; str++)
			if (*str == '\0')
				return (NULL);
		return ((char *)str);
	}

In effect, strchr() can be used to `dequalify' a pointer:

	const char *ccp;
	char *cp;

	cp = strchr(ccp, *ccp);	/* dequalify */

If the language is going to provide type checking, strchr() should be
a function of `optionally-const char *' returning `typeof arg1'.
Since it is not, and since example like strchr() are rather more
frequent than I originally expected, I would rather it did not even
pretend to provide such checking.  I believe things would be `better'
if the language freely allowed conversion between `char **' and
`const char **' and `char * const *' and `const char * const *', for
instance.
-- 
In-Real-Life: Chris Torek, Lawrence Berkeley Lab EE div (+1 415 486 5427)
Berkeley, CA		Domain:	torek at ee.lbl.gov