$extendedSyntax

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:

{$extendedSyntax off} var

   p: pChar;

begin

   p := nil;
   inc(p, 42); { no problem }

end.

Similarly, unusual comparison operations may be accessible with foreign routines.

• Built-in functions can never be called as if they were procedures

{$extendedSyntax on} begin

   pi; { discardFunctionResultDemo.pas(4,4) Error: Illegal expression }

end.

even though a custom pi function doing exactly the same would be acceptable.

• 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

• Standard Pascal does not define any of those “extensions”.

See also

• Pascal for C users

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From the Free Pascal wiki, page "$extendedSyntax", as it stood on 2022-10-23 after a change by Bart, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.