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Revision 1 of 3, by Bart on 10-23-2022. The page as it is now.

$extendedSyntax

The global compiler directive

pascal

{$extendedSyntax on}

turns on additional syntax. The FPC has this by default on. The short notation is

pascal

{$X+}

/

pascal

{$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
pascal
```
record
```
into a managed data type.
Integer arithmetic expressions are allowed on pointers. The directive [[$pointerMath|
pascal
```
{$pointerMath}
```
]] had to be on for that during the respective pointer type’s definition.
Pointers become ordered and can be compared using [[Less than|
pascal
```
<
```
]],[[Greater than|
pascal
```
>
```
]],
pascal
```
<=
```
and
pascal
```
>=
```
. Typed pointers have to correspond to each other. The [[Equal|
pascal
```
=
```
]] and [[Not equal|
pascal
```
<>
```
]] comparisons work regardless of the
pascal
```
{$extendedSyntax}
```
state.

Notes

If you have
pascal
```
{$extendedSyntax off}
```
, you can still do pointer arithmetic with routines from other units if they have been compiled with
pascal
```
{$extendedSyntax on}
```
, for example [[Inc and Dec#Special behaviors|
pascal
```
inc
```
and
pascal
```
dec
```
]]:

{$extendedSyntax off} var

p: pChar;

begin

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

end.

</syntaxhighlight>

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.

</syntaxhighlight>

even though a custom [https://www.freepascal.org/docs-html/rtl/system/pi.html

pascal

pi

pascal

function

] doing exactly the same would be acceptable.

Although with
pascal
```
{$extendedSyntax on}
```
pointers become ordered, they do not become ordinal data types; the standard functions [[Ord|
pascal
```
ord
```
]],
pascal
```
succ
```
and
pascal
```
pred
```
are still not applicable on pointers.

Comparative remarks

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

See also

Pascal for C users

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.