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
