Compile time string hashing

I don't know of a way to do this with the preprocessor or with templates. I suspect your best bet is to create a separate pre-compile step (say with perl or such) to generate the hash_cstring statements from a set of source statements. Then at least you don't have to split the strings manually when you add new ones, and the generation is fully automated and repeatable.

Templates can be instantiated with any external symbol, therefore this should work as expected:

external char const* object_method = "object.method";
... = hash_cstring<object_method>::value;

(given the template hash_cstring<> is able to deal with pointer values).

Solution with gcc-4.6:

#include <iostream>
template<size_t N, size_t I=0>
struct hash_calc {
    static constexpr size_t apply (const char (&s)[N]) {
       return  (hash_calc<N, I+1>::apply(s) ^ s[I]) * 16777619u;
    };
};

template<size_t N>
struct hash_calc<N,N> {
    static constexpr size_t apply (const char (&s)[N]) {
       return  2166136261u;
    };
};

template<size_t N>
constexpr size_t hash ( const char (&s)[N] ) {
    return hash_calc<N>::apply(s);
}

int main() {
   char a[] = "12345678";
   std::cout << std::hex << hash(a) << std::endl;
   std::cout << std::hex << hash("12345678") << std::endl;
}

http://liveworkspace.org/code/DPObf

I`m happy!