UPDATE: After some additional reading, what I really wanted was guaranteed early binding (which should translated to an immediate call for non-virtual functions and non-PIC code), which can be done by passing a (member) function as a template parameter. The problem I had was that gcc < 4.5 and icc 11.1 can generate some funky instructions for member function pointer template parameter calls. AFAICT, gcc >= 4,5 and vs2008 handle these template parameter calls fine.
First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens).
The idea is that when you make a conventional function call, it compiles to something like this:
callq <immediate address>
But if you make a function call using a function pointer, it compiles to something like this:
mov <memory location>,%rax
callq *%rax
Which is all well and good. However, what if I’m writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to
template <int int_literal>
struct my_template {...};`
I’d like to write
template <func_literal_t func_literal>
struct my_template {...};
and have calls to func_literal within my_template compile to callq <immediate address>.
Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language?
If you use a function pointer type in your template and instantiate it with a fixed function, then the compiler should use a direct call for that function pointer call.