How to reliably get size of C-style array?

Question

How do I reliably get the size of a C-style array? The method often recommended seems to be to use sizeof, but it doesn\'t work in the foo function

Answer 1

You can either pass the size around, use a sentinel or even better use std::vector. Even though std::vector lacks initializer lists it is still easy to construct a vector with a set of elements (although not quite as nice)

static const int arr[] = {1,2,3,4,5};
vector vec (arr, arr + sizeof(arr) / sizeof(arr[0]) );

The std::vector class also makes making mistakes far harder, which is worth its weight in gold. Another bonus is that all C++ should be familiar with it and most C++ applications should be using a std::vector rather than a raw C array.

As a quick note, C++0x adds Initializer lists

std::vector v = {1, 2, 3, 4};

You can also use Boost.Assign to do the same thing although the syntax is a bit more convoluted.

std::vector v = boost::assign::list_of(1)(2)(3)(4);

or

std::vector v;
v += 1, 2, 3, 4;