Question

I know I can pass a function pointer as a template parameter and get a call to it inlined but I wondered if any compilers these days can inline an ‘obvious’ inline-able function like:

inline static void Print()
{
 std::cout << "Hello\n";
}

....

void (*func)() = Print;

func();

Under Visual Studio 2008 its clever enough to get it down to a direct call instruction so it seems a shame it can’t take it a step further?

Answer 1

GNU’s g++ 4.5 inlines it for me starting at optimization level -O1

main:
    subq    $8, %rsp
    movl    $6, %edx
    movl    $.LC0, %esi
    movl    $_ZSt4cout, %edi
    call    _ZSt16__ostream_insertIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_E
    movl    $0, %eax
    addq    $8, %rsp
    ret

where .LC0 is the .string “Hello\n”.

To compare, with no optimization, g++ -O0, it did not inline:

main:
    pushq   %rbp
    movq    %rsp, %rbp
    subq    $16, %rsp
    movq    $_ZL5Printv, -8(%rbp)
    movq    -8(%rbp), %rax
    call    *%rax
    movl    $0, %eax
    leave
    ret