Re: [boost] Looking for thoughts on a new smart pointer: shared_ptr_nonnull

On Oct 8, 2013, at 2:37 PM, Daniel James wrote:

On 6 October 2013 19:14, Matt Calabrese wrote:

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On Sun, Oct 6, 2013 at 2:11 AM, Daniel James wrote:

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How is that not introducing undefined behaviour? Say there's a function:

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void foo(boost::shared_ptr<...> const& x) { if (!x) { something_or_other(); } else blah_blah(*x); }

By using shared_ptr_nonull, that check can be removed:

void foo(boost::shared_ptr_nonnull<...> const& x) { blah_blah(*x); }

But then a caller believes that their shared_ptr is never null, so they copy it into a shared_ptr_nonnull without checking for null first, and that action introduces the possibility of undefined behaviour where there was none before (given that there's always a possibility of bugs in non-trivial code).

No response to this example?

Why does the author of foo() know enough to test for null, but the caller of foo(), knowing that they are creating a shared_ptr_nonnull, doesn't? ___ Rob (Sent from my portable computation engine)