Can std::hash be used to hash function pointers?

Question

Can the C++11 std::hash type be used to hash function pointers? There is a hash partial specialization defined as

template 

        

Answer 1

It's actually interesting... I bumped into this question while using MSVC++. What I'm trying to do is:

static std::unordered_map FunctionMap()
{
    static std::unordered_map map;
    return map;
}

with Fun a function pointer type.

During compilation, I get the following error:

error C2338: The C++ Standard doesn't provide a hash for this type.
....
_Kty=int (__thiscall Testje::* )(int,int)

In a previous attempt I attempted to cast the function pointer to void*, which isn't allowed and doesn't compile (see: https://isocpp.org/wiki/faq/pointers-to-members#cant-cvt-memfnptr-to-voidptr for details). The reason is that a void* is a data pointer, while a function pointer is a code pointer.

My conclusion so far is that it isn't allowed and it won't compile on MSVC++.