[m-rev.] for review: add dir.current_directory

[Peter Wang]

On 2007-09-19, Peter Ross <pro at missioncriticalit.com> wrote:
> >
> > +:- pragma foreign_proc("C",
> > +    dir.current_directory(Res::out, IO0::di, IO::uo),
> > +    [may_call_mercury, promise_pure, tabled_for_io, terminates],
> > +"
> > +    size_t      size = 256;
> > +    char        *buf;
> > +    MR_String   str;
> > +
> > +    while (1) {
> > +        buf = MR_GC_NEW_ARRAY(char, size);
> > +        if (getcwd(buf, size)) {
> > +            MR_make_aligned_string(str, buf);
> > +            Res = ML_make_io_res_1_ok_string(str);
> > +            break;
> > +        }
> > +        if (errno != ERANGE) {
> > +            ML_make_io_res_1_error_string(errno,
> > +                MR_make_string_const(""dir.current_directory failed: ""),
> > +                &Res);
> 
> You should use strerror to get the actual error message.

ML_make_io_res_1_error_string does that.

> Note don't forget to test if the result is the empty string, in which
> case a more informatiive error message would be useful.

If that can happen it should be handled in ML_maybe_make_err_msg which
is called by everything else.

Peter

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