Re: C vs. Ada - strings

[Florian Weimer <fw@deneb.cygnus.argh.org>]

Robert Dewar <robert_dewar@my-deja.com> writes:

> In article <wcc7lda9qzc.fsf@world.std.com>,
>   Robert A Duff <bobduff@world.std.com> wrote:
> > > At least I think it's impl dependent -- perhaps I remembered
> > > wrong, and it's always false :-)
> >
> > I think you remembered correctly.

> I guess it's always false in K&R, unspecified in ANSI, is that
> right?

I'm sure that back in the old days, C didn't have string constants.
Occasionally, you still see things like

        mktemp("/tmp/fileXXXXXX"),

and mktemp() does write to the array argument.  (Of course, you should
never-ever use mktemp(), tmpnam() or tempnam().  Note that there is at
least one Ada implementation which uses tmpnam() internally to create
a name name for Ada temporary files, so be careful there as well.)

Of course, nowadays, there are compilers which merge identical string
constants, and linkers which put string constants into read-only data
sections, and C99 says indeed:

| It is unspecified whether these arrays are distinct provided their
| elements have the appropriate values.  If the program attempts to
| modify such an array, the behavior is undefined.