----- Mensaje original ----- De: David Abrahams <dave@boost-consulting.com> Fecha: Domingo, Marzo 13, 2005 0:52 am Asunto: [boost] Re: [review] hash functions
Alberto Barbati <abarbati@iaanus.com> writes:
Ah! And there's one more case in which we are helpless, although I'm curious to see an implementation that exploits such latitude: the wording used in the standard does not guarantee that the mapping from pointers to integers always produce the same value over time. In other words:
char* p = new char; size_t i1 = reinterpret_cast<size_t>(p); size_t i2 = reinterpret_cast<size_t>(p); assert(i1 == i2); // ??? char* q1 = reinterpret_cast<char*>(i1); char* q2 = reinterpret_cast<char*>(i2); assert(p == q1 && q1 == q2);
The standard guarantees that the second assert passes, but says nothing about the first assert.
There are other cases too. reinterpret_cast could map all pointers to the same integer.
If you allow me to be a little pedantic, this is not the case. reinterpret_cast<> guarantees back conversion, so it can't possibly map every pointer into the same integer. As for the rest of your argument, I agree 100%. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo