@

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@

The address operator @ returns the address of a variable, procedure or function.

Normally, the value @ returns is an untyped pointer. If you are handling pointers a lot, and want to mitigate issues with passing references of wrong type's target, you have use the directive {$typedaddress on}.

Here some example to demonstrate, what produces with untyped pointers valid and functional code, but semantically outputs an erroneous result:

 0program untypedAddressDemo(input, output, stderr);
 1
 2procedure incrementIntByRef(const ref: PByte);
 3begin
 4	inc(ref^);
 5end;
 6
 7var
 8	foo: integer;
 9begin
10	foo := -1;
11	incrementIntByRef(@foo);
12	writeLn(foo);
13end.

It was intended, that 0 (zero) gets printed, but the program prints -256 instead. With {$typedaddress on} compilation fails with an incompatible type error. You usually want the latter behavior (compile-time failure) instead of wasting time with hours of debugging.

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• The @ operator
• Typed address operator (@)