Using and Porting GNU Pascal

Go to the first, previous, next, last section, table of contents.

Data types

Generic Pointer: There is no built-in untyped Pointer in GNU Pascal. Use `^Void' to define it.

Integer types: There is no built-in Byte, Word, etc. in GNU Pascal. Use the modifiers `__byte__', `__short__', `__long__' and `__unsigned__' (described in See section GNU Pascal extensions) to define them.

  Borland Pascal          GNU Pascal

  shortint                __byte__ Integer
  Integer                 __short__ Integer
  LongInt                 Integer = __long__ Integer
  Comp                    __longlong__ Integer
  Byte                    __unsigned__ __byte__ Integer
  Word                    __unsigned__ __short__ Integer
    -                     __unsigned__ __long__ Integer
    -                     __unsigned__ __longlong__ Integer

Real types: There is no built-in `Single', `Double', `Extended' in GNU Pascal; Real has 8 bytes on an Intel-x86 machine. Use `__short__ Real' to define `Single', `__long__ Real' to define `Extended'.

  Borland Pascal          GNU Pascal

  Single                  __short__ Real
  Real                      -
  Double                  Real
  Extended                __long__ Real
  Comp                    __longlong__ Integer

A KNOWN BUG: You cannot writeln variables of a type with a __ modifier. To work around, cast them to their basis type (Integer or Real) when writelning them:

  Var
    x: __long__ Real;

  writeln ( Real ( x ) );

Complex numbers: According to Extended Pascal, GNU Pascal has built-in complex numbers.
Record types: GNU Pascal alignes 32-bit fields on 4-byte addresses. Thus the record
```
  Type
    myRec = record
      f, o, oo: Boolean;
      Bar: Integer;
    end (* myRec *);
```
has 8 bytes, not 7.
Instead of procedural types, GNU Pascal has pointers to procedures:
```
    Type
      FuncPtr = ^Function ( Real ): Real;
```
Furthermore, GNU Pascal supports Standard Pascal's procedural parameters--see below.

Go to the first, previous, next, last section, table of contents.