CODEWITHSUNDEEP
delphivariablesmemoryallocation
miodrag
miodrag

Reputation: 99

how to force delphi compiler to allocate memory for unused variables

I realized (the hard way, an hour of debugging) that my Delphi 2010 compiler with optimization off (and record alignment of 1 byte) does not allocate memory for unused variables. If they are defined like:

var x,y,z:longint; a1,a2,a3:whatever;

and y gets unused (actually, i removed a form from the project temporarily, which references that variable exclusively), then z is assigned the address of x+4. Nice except that i have a lot of code which will now mix z with a1. Can this be controlled by some switch? Thank you.

Upvotes: 0

Views: 382

Answers (1)

Arnaud Bouchez
Arnaud Bouchez

Reputation: 43023

This won't work. The compiler will optimize all unused variables.

What you can do is to define a packed record, as such:

type
  TMyData = packed record
    x,y,z: longing;
    a1,a2,a3: whatever;
  end;

Then the allocated TMyData will always be allocated as one, including all internal variables, even if they are not used in your code.

For temporary variables allocated on the stack, you may use:

function DoSomething();
var loc: packed record
      x,y,z: longing;
      a1,a2,a3: whatever;
    end;
begin
  loc.x := 10;
  ...

Upvotes: 4

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