[Qt-interest] Undefined behavior in QString::toStdWString() ?

[Thiago Macieira]

Robert Hairgrove wrote:
>Thank you for your reply. I just tried doing something similar to what
>is done in the function QString::toStdWString, i.e.:
>
>=== code starts ===
>#include <iostream>
>#include <ostream>
>#include <string>
>
>int main()
>{
>   std::string s;
>   std::string::iterator it = s.end();
>   char * x = &(*(it));
>   std::cout << reinterpret_cast<unsigned int>(x) << std::endl;
>}
>=== code ends ===
>
>Everything compiles and seems to run normally, regardless of whether I
>use begin() or end(). However, I just wonder how safe this is?

Very, unless the implementation is broken.

The line: char *x = &(*(it));
is actually: char *x = &(it.operator*());
and std::string::operator*() is supposed to return char&. The & we added 
turns it back into a pointer (i.e., char *). That means we haven't 
dereferenced anything yet.

-- 
Thiago Macieira - thiago.macieira (AT) nokia.com
  Senior Software Engineer - Nokia, Qt Software
  Qt Software is hiring - ask me
      Sandakerveien 116, NO-0402 Oslo, Norway
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