Re: [PATCH] Change some arguments to gdb::string_view instead of name+len

["Christian Biesinger via gdb-patches" <gdb-patches@sourceware.org>]

On Tue, Oct 1, 2019 at 1:23 PM Pedro Alves <palves@redhat.com> wrote:
>
> On 10/1/19 6:33 PM, Christian Biesinger via gdb-patches wrote:
> > -  if (linkage_name[len] != '\0')
> > +  /* Don't use string_view::operator[] because we are accessing beyond
> > +     the size of the string_view, which is technically unsupported.  */
> > +  if (linkage_name.data ()[linkage_name.length ()] != '\0')
> >      {
> >        char *alloc_name;
>
> It's more than just unsupported, it's undefined behavior.  If we're promising
> the string_view interface, then it's supposedly valid to pass in a string_view
> that happens to point just at the end of a page, with the one-past-the-end
> byte living in an unmapped page.  Dereferencing the one-past-end byte in
> that case SIGSEGVs.

That's true (though also a pre-existing issue).

> > -  if (ms_type == mst_file_text && startswith (name, "__gnu_compiled"))
> > +  if (ms_type == mst_file_text && startswith (name.data (), "__gnu_compiled"))
> >      return (NULL);
> >
>
> This, via startswith also assumes that name.data() is a null-terminated
> string.

Ah yes. I'll add a startswith version that takes string_views.

> I wonder whether we should have a zstring_view type.  like string_view, but
> assumes/requires null-terminated.

How does that solve anything? This function can (apparently) take
non-null terminated strings, so zstring_view wouldn't work?

Christian