c++ - Is it an undefined behavior to access a pointer to an empty vector element? -

this code works expected:

std::vector<unsigned char> tab; if(!&tab[0])std::cout<<"null"; 

but not sure if it's legal treat &tab[0] null when vector empty.

what expecting &tab[0] null, not if vector empty or not.

it's can pass function accepts const unsigned char*

i'm not sure if meant unitialized (vector element) or (uninitialized vector) element, example neither. it's initialized vector of 0 elements.

a.operator[n] defined have semantics of *(a.begin()+n), , begin = end empty vector, you're dereferencing end iterator. behaviour undefined.