Using vector<char> as a buffer without initializing it on resize()

It is a known issue that initialization can not be turned off even explicitly for std::vector.

People normally implement their own pod_vector<> that does not do any initialization of the elements.

Another way is to create a type which is layout-compatible with char, whose constructor does nothing:

struct NoInitChar
{
    char value;
    NoInitChar() noexcept {
        // do nothing
        static_assert(sizeof *this == sizeof value, "invalid size");
        static_assert(__alignof *this == __alignof value, "invalid alignment");
    }
};

int main() {
    std::vector<NoInitChar> v;
    v.resize(10); // calls NoInitChar() which does not initialize

    // Look ma, no reinterpret_cast<>!
    char* beg = &v.front().value;
    char* end = beg + v.size();
}

There's nothing in the standard library that meets your requirements, and nothing I know of in boost either.

There are three reasonable options I can think of:

• Stick with std::vector for now, leave a comment in the code and come back to it if this ever causes a bottleneck in your application.
• Use a custom allocator with empty construct/destroy methods - and hope your optimiser will be smart enough to remove any calls to them.
• Create a wrapper around a a dynamically allocated array, implementing only the minimal functionality that you require.

Encapsulate it.

Initialise it to the maximum size (not reserve).

Keep a reference to the iterator representing the end of the real size, as you put it.

Use begin and real end, instead of end, for your algorithms.