Re: [Boost-Users] Why not "if (px != rpx) " ?

14 Dec 2001


      From: "Louis Lavery" 
...
Hello,
The following is use by the boost shared_ptr assignment operators
(see boost\smart_ptr.hpp)...
void share(T* rpx, long* rpn) {
      if (pn != rpn) { // Q: why not px != rpx? A: fails when both == 0
         ++*rpn; // done before dispose() in case rpn transitively
                 // dependent on *this (bug reported by Ken Johnson)
         dispose();
         px = rpx;
         pn = rpn;
      }
   } // share
...I curious to know what it means by "fails when both == 0".
It's possible that px == rpx == 0, yet pn != rpn.

--
Peter Dimov
Multi Media Ltd.