which cast is faster static_cast<int> () or int()

Question

Try to see which cast is faster (not necessary better): new c++ case or old fashion C style cast. Any ideas?

Answer 1

There should be no difference at all if you compare int() to equivalent functionality of static_cast<int>().

Using VC2008:

    double d = 10.5;
013A13EE  fld         qword ptr [__real@4025000000000000 (13A5840h)] 
013A13F4  fstp        qword ptr [d] 
    int x = int(d);
013A13F7  fld         qword ptr [d] 
013A13FA  call        @ILT+215(__ftol2_sse) (13A10DCh) 
013A13FF  mov         dword ptr [x],eax 
    int y = static_cast<int>(d);
013A1402  fld         qword ptr [d] 
013A1405  call        @ILT+215(__ftol2_sse) (13A10DCh) 
013A140A  mov         dword ptr [y],eax 

Obviously, it is 100% the same!

Answer 2

No difference whatsoever.

When it comes to such basic constructs as a single cast, once two constructs have the same semantic meaning, their performace will be perfectly identical, and the machine code generated for these constructs will be the same.

Answer 3

I believe that the actual result is implementation defined. You should check it in your version of compiler. But I believe that it will give the same result in most modern compilers. And in C++ you shouldn't use C-cast, instead use C++ casts - it will allow you to find errors at compile time.