How to check whether all bytes in a memory block are zero

Question

I have a block of memory with elements of fixed size, say 100 bytes, put into it one after another, all with the same fixed length, so memory looks like this

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Answer 1

I can't believe no one posted this yet... a solution that actually looks like C++ and isn't UB for breaking aliasing rules:

#include  // std::all_of
#include    // std::size_t

// You might only need this
bool
memory_is_all_zeroes(unsigned char const* const begin,
                     std::size_t          const bytes)
{
    return std::all_of( begin, begin + bytes,
                        [](unsigned char const byte) { return byte == 0; } );
}

// but here's this as a bonus
template
bool
array_is_all_zeroes( T_Element const (& array)[T_count] )
{
    auto const begin = reinterpret_cast(array);
    auto const bytes = T_count * sizeof(T_Element);

    return memory_is_all_zeroes(begin, bytes);
}

int
main()
{
    int const blah[1000]{0};

    return !array_is_all_zeroes(blah);
}

This might not satisfy some people's assumptions about efficiency (which are just that, assumptions, until profiled), but I think being valid and idiomatic code are much in its favour.