c++ extract the template arugments of a function pointer

Question

Is there a way to extract/introspect on templated function pointer to get its template argument types and size?

More generally speaking, what kind of Callables/Invocables in C++ are able to be introspected to get the type info of template args and what are the techiniques?

Edit: What I'm trying to do is to pass a callable object to some other class as a template parameter and carrying all the info this callable has regarding what template parameters it takes. Then I invoke this callable in a more compile-time and functional friendly way.

https://godbolt.org/z/q3f98177Y

template<typename T>
T SomeFunc() {return T{};}

constexpr auto some_func_fp = &SomeFunc<int>;
// can we do some introspection to get the types 
// and size of the template arguments of some templated function pointers?

Answer 1

You can't, in general, the function's type (and the pointer type) has nothing to do with the template parameter. (in your case you can detect the return type though)

---

#include <type_traits>

template<typename T>
int SomeFunc(){return 0;}

auto fi = &SomeFunc<int>;
auto ff = &SomeFunc<float>;

// fi has same type as ff, int(*)()
static_assert(std::is_same_v<decltype(fi),decltype(ff)>);