[boost] Re: Maybe generic meta-programming

From: Bill Wade (bill.wade_at_[hidden])
Date: 1999-12-01 10:10:44

> Dave wrote

> 2. The problem you describe is no worse than many other pitfalls in the
> language; you have to know the language rules.
>
> e.g.
>
> class mutex;
> void foo()
> {
>     mutex();    // Oops; does nothing!
> }

A trick to consider (I've never actually used this) is to require a mutex&
as an unused argument in all constructors.  So

  mutex();	      // Compiler error
  mutex m = m;	// Ok

or

  foo(args);		// Compiler error
  foo f = foo(args, f);	// Ok

The only way to create a temporary is with the help of some non-temporary
that happens to be available.  It doesn't seem like a likely mistake for
classes like require and mutex.