Question

Is there any way to create a hash of string at compile time using the C/C++ preprocessor (or even template-metaprogramming)?

e.g. UNIQUE_SALT("HelloWord", 3DES);

The idea is that HelloWorld will not be present in the compiled binary, just a hash.

Edit: There are many of these declarations spread over a large codebase.

Answer 1

With C++0x, this is possible as covered by answers in #1 and #2.

In C++03 there was no compile time string processing. With the preprocessor you can’t seperate the string into tokens, with templates you can’t access single characters. There was however a discussion on the speculated approach using C++0x.

What you could do for C++03 is to pass the string character-wise (possible using multi-character literals):

foo = hash<3DES, str<'a','b','c'> >::result;
// or:
foo = hash<3DES, str<'abc','def'> >::result;

… or simply do it as a pre-build step.