If you have an STL vector which has been resized, is it safe to take the address of element 0 and assume the rest of the vector will follow in memory?
// do some stuff with vc
char* p = &vc;
// do stuff with *p
Yes, that is a valid assumption (*).
From the C++03 standard (126.96.36.199):
The elements of a vector are stored contiguously, meaning that if v is a vector where T is some type other than bool, then it obeys the identity &v[n] == &v + n for all 0 <= n < v.size().
(*) ... but watch out for the array being reallocated (invalidating any pointers and iterators) after adding elements to it.