From owner-cvs-all  Thu Sep  6  9:21:44 2001
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From: Bruce Evans <bde@zeta.org.au>
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To: Mark Murray <mark@grondar.za>
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Subject: Re: cvs commit: src/usr.bin/su Makefile su.c 
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On Wed, 5 Sep 2001, Mark Murray wrote:

> > > markm       2001/09/04 10:10:57 PDT
> > >
> > >[...]
> > >
> > >   This solves the problem (in my own mind) of how a "const char *" _ever_
> > >   actually gets a value in a WARNS=2 world.
> >
> > const char *foo = "bar"; ???
>
> Right :-).
>
> Now how do you get (variable) stuff into a 'const char *'?

	/* Initialize `foo' in its declaration would be a style bug. */
	const char *foo;
	...
	foo = variable_stuff();		/* What's the problem? */

> For example -  a function is not allowed to modify its arguments, so
> they are const, but the stuff being passed in is by no means constant.
> That one is easy - you can pass a 'foo *' into a 'const foo *'. Now,

Initializing the "const char *" is easy because it is essentially the
same as this.

> how do you build up a 'const foo *' in such a way that you can, but
> nobody else can?

This question is sort of backwards too.  You want to get const
non-built-up stuff into a plain "char *".

> Like perl's un-tainting, C needs a formal un-consting, and I guess
> this is it.

It's just a cast to non-const in ISO C.  gcc -Wcast-qual emits warnings
that some would consider spurious.  But you asked for them by setting
WARNS=2.

Bruce


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