🚀 go-pugleaf

pjl@sparc10.cs.uiuc.edu (Paul Lucas) writes:
|	IMHO, the ability to *depend upon* the (desired) fact that
|	*calling* a non-virtual member-function with a nil pointer is
|	*guaranteed* to be harmless seems worthwhile (and its addition
|	to the language wouldn't break anything as far as I can tell).

If this change to the language were made, it might be appropriate
not to include the case of calling a member function with a nil
pointer to a class virtually derived from the class where the
function is defined:

   class Base { void f(); };
   class Derived : public virtual Base {};
   ...
   Derived* p;
   p->f();

If I understand correctly, in most implementations the conversion
of p to a Base* will require examining the contents of *p.
If p may be 0, then the compiler must insert extra code to
treat this case correctly.

Of course, this extra code is currently necessary for all conversions
of a Derived* to a Base* where the compiler can't be sure that
the pointer is non-nil.  So perhaps the extra overhead for the
function calls wouldn't be seen as significant.

-- 
Patrick Smith
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