[v3] char_traits error checking

[Nathan Myers]

On Tue, Mar 12, 2002 at 10:49:36AM -0500, Phil Edwards wrote:
> On Mon, Mar 11, 2002 at 09:35:02PM -0800, Benjamin Kosnik wrote:
> > 
> > 21.3.1 - basic_string constructors
> > basic_string(const charT* s, const Allocator& a = Allocator());
> > -9- Requires:  s shall not be a null pointer.
> 
> I looked at this as part of PR 5258.  The way the ctors are arranged in
> basic_string.tcc doesn't seem to give us any opportunities to do checking on
> the arguments:  the string data is built (and dereferenced) in the member
> init list, so no "if NULL throw logic_error" is possible unless we break
> that out into a ctor body.

Not a problem -- change ": member(p)" to ": member(__throw_if_null(p))".

> As for the member functions, if we make "no NULL pointers" a string class
> invariant / postcondition, those problems are neatly sidestepped.

For string, it's worth giving a decent diagnostic for null pointers
even though we don't have to.  Beginners rely very heavily on string.

Nathan Myers
ncm at cantrip dot org