On Fri, Dec 18, 2009 at 9:16 AM, Emil Dotchevski <emildotchevski@gmail.com> wrote:
On Thu, Dec 17, 2009 at 12:19 PM, Dean Michael Berris <mikhailberis@gmail.com> wrote:
I don't understand why it's "completely useless" when in cases where they are done wrong it can cause a runtime crash.
Because the information the compiler gives you in this case is "you have used reinterpret_cast, your program *might* violate the C++ standard" but it can't know if you're violating it or not. So what it really says is "warning, you're using reinterpret_cast" which is useless because you know that you are using reinterpret_cast.
Are we still talking about the strict aliasing rules? Because the strict aliasing stuff doesn't happen only where reinterpret_cast is done. In the case of Boost.Optional and GCC 4.4 (which apparently has a bug specific to this case) it's saying accessing a certain area in memory whose pointer is cast to be a pointer to a type which might not be related to the original type of the data in that area in memory *may* cause a runtime error. This is one of the reasons why I really don't like pointers in C/C++ -- the fact that its type can be modified in a standard manner makes it really really dangerous. But then that's a completely different matter altogether. ;)
To someone who doesn't know the semantics of reinterpret_cast, perhaps the warning has some value, but for the rest of us what it really says is "Warning! You have used reinterpret_cast!"
Sure, but isn't reinterpret_cast considered bad because of the fact that there is no standard implementation of it?
I'm not sure what you mean. There is a standard implementation of reinterpret_cast.
Really? I thought this was implementation-defined? If you mean 'static_cast<foo*>(static_cast<void*>(bar_ptr))' I don't think it's guaranteed that that's really how reinterpret_cast is implemented by compilers. -- Dean Michael Berris blog.cplusplus-soup.com | twitter.com/mikhailberis linkedin.com/in/mikhailberis | facebook.com/dean.berris | deanberris.com