$extendedSyntax

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The global compiler directive {$extendedSyntax on} turns on additional syntax. The FPC has this by default on. The short notation is {$X+}/{$X‑}.

Affected syntax

  • Functions can be called as if they were procedures. The function result is discarded. This is potentially harmful if, for example, the function allocated new memory space and returned a pointer to it. Nonetheless, managed data types are insusceptible to leakage. Implementing a management operator can turn any record into a managed data type.
  • Integer arithmetic expressions are allowed on pointers. The directive {$pointerMath} had to be on for that during the respective pointer type’s definition.
  • Pointers become ordered and can be compared using <,>, <= and >=. Typed pointers have to correspond to each other. The = and <> comparisons work regardless of the {$extendedSyntax} state.

Notes

  • If you have {$extendedSyntax off}, you can still do pointer arithmetic with routines from other units if they have been compiled with {$extendedSyntax on}, for example inc and dec:
    program pointerMathDemo(input, output, stdErr);
    {$extendedSyntax off}
    var
    	p: pChar;
    begin
    	p := nil;
    	inc(p, 42); { no problem }
    end.
    
    Similarly, unusual comparison operations may be accessible with foreign routines.
  • Although with {$extendedSyntax on} pointers become ordered, they do not become ordinal data types; the standard functions ord, succ and pred are still not applicable on pointers.

Comparative remarks

See also