Question

I’ve been having a strange problem that I’ve never seen before. Now I have a for loop:

var
 a,counter: byte;
begin
  a:=0; 
   for counter := 1 to 10 do//I put a breakpoint at this line
   begin
     a:=a*5;
     a:=a+counter;
   end;
end;

If I put a breakpoint at the line above and try to step into the loop I can’t do it. The debugger immediately steps over the loop and goes to the end.In the end I get the right result, but I can’t follow the loop step by step. I mean this is just a simple example and not the real task. I just want to know when in what circumstances does this happen? I definitely remember tracking through all the steps of a loop. I work with Delphi 2010.

Answer 1

Both lines of code in the loop can be completely optimized away; you do nothing with a outside the loop, so both of the assignments are unnecessary. After the optimization, the compiler is leaving

for counter := 1 to 10 do 
  ;

Actually, if you didn’t have a breakpoint there, the loop would be removed as well, as it does nothing.

If you’re having problems with your code, and the info above doesn’t help (using the variable a after the loop runs), you need to post your real code. This made-up code is very clear to analyze; the problem in your actual code may be this simple, or much more complex to analyze.