Re: Ichbiah 2022 compiler mode

On 21/12/2024 17:19, G.B. wrote:

On 21.12.24 09:14, Randy Brukardt wrote:
 

Note that :
1. I have no statistics, but it seems to me that there is more variables
than constants in my code.

>
But how many of them *have* to be variables vs. the number that just are
because it is easier? I know I have a number of the latter.
>

2. I say "Useless" from my coder point of view, I dont know if it simplify
the work for compiler or tools implementers.

>
Constants do help the compiler generate better code, although a lot of the
benefits can be gained also by working harder. (That's what C compilers do,
after all.)

 What are some compilers offering today? That is, can they find declarations
of variables that could be constants, if so instructed?
I am seeing some warnings about non-initialized variables for a meaningless
mock-up, but not much else.  Ada, C++, Java.
(Maybe there are options that I have missed. Or an analysis of a whole
program yields more.)
 function testc (b : Boolean) return Integer is
    package P is
      x : Integer;
    end;
begin
   if b then
      P.x := 42;
   end if;
   return P.x;
end testc;
 int testc(bool b) {
    struct {
      int x;
    } P;
    if (b) {
      P.x = 42;
    }
    return P.x;
}
 class testc {
   class P {
     int x;
   }
   P P;
   int $(boolean b) {
     if (b) {
        P.x = 42;
     }
     return P.x;
   }
}
 

My understanding is that many compliers will optimise these, and if trivial numbers will 'optimise' out the variable. Confusing in the debugger!
--
Chris