shared_ptr::operator-> does not fail for nullptr

[Marc Glisse]

On Wed, 11 Jun 2014, Christoph Mathys wrote:

> Hi, I hope I found the right list.
>
> I stumbled across this (at least for me) surprising behaviour of
> std::shared_ptr. I can call operator-> or operator* on an empty
> shared_ptr, but my program will not crash in all cases.
>
> I'll try to illustrate my problem with examples:
> std::shared_ptr<int> pi;
> int& i = *pi; // no crash ?!?

references are syntactic sugar around pointers, to the compiler this is 
roughly:
int* i_ptr = pi.get();

> This is a bug in my program, but the program only crashes when it
> tries to access i, which might be quite far away from where I made the
> mistake.
>
>
> std::shared_ptr<int> pi2;
> int i2 = *pi2; // crash segfault
>
> Here, my program will crash right when dereferencing the pointer.
>
> Now, is this the expected behaviour of shared_ptr? Do I need to check
> myself that my smart_ptr is non-nil similar to "manual" bounds
> checking when using operator[] on std::vector?
>
> I tested this using gcc 4.6.4 and 4.8.1 on Linux with c++11 enabled.
> Just for information: The shared_ptr of boost 1.54 crashes with a
> failed assertion.

If you compile with -D_GLIBCXX_DEBUG there will be an assertion.

-- 
Marc Glisse