🚀 go-pugleaf

Lars Farm (lars.farm@nts.mh.se) wrote:
:      5.2.6  Dynamic cast                           [expr.dynamic.cast]
:    ...
:    6 Otherwise,  v shall be a pointer to or an lvalue of a polymorphic type
:    ...
: What should happen when 'v' is not a pointer to or an lvalue of a
: polymorphic type? return 0? crash? throw bad_cast? undefined?

No, the compiler should produce a diagnostic, see [intro.compliance]
paragraphs 1 through 3.

:    ...
:    8 The  run-time  check  logically  executes  like  this: 
:      [...]  Otherwise, the run-time  check fails.

: If fail means undefined, why not require that it returns 0?

This one is made pretty clear in the following paragraph:

9 The value of a failed cast to pointer type is the null pointer value
  of the required result type.  A failed cast to reference type throws
  bad_cast (_lib.bad.cast_).

-- 
        Tony Cook - tony@online.tmx.com.au
                    100237.3425@compuserve.com
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