The GNU Modula-2 front end to GCC
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DEFINITION MODULE SYSTEM;
(* Gives access to system programming facilities that are probably
non portable. *)
(* The constants and types define underlying properties of storage *)
EXPORT QUALIFIED BITSPERLOC, LOCSPERWORD,
LOC, ADDRESS, BYTE, WORD, INTEGER8,
INTEGER16, INTEGER32, INTEGER64, CARDINAL8,
CARDINAL16, CARDINAL32, CARDINAL64, WORD16,
WORD32, WORD64, BITSET8, BITSET16,
BITSET32, REAL32, REAL64, REAL128,
COMPLEX32, COMPLEX64, COMPLEX128, CSIZE_T,
CSSIZE_T,
ADDADR, SUBADR, DIFADR, MAKEADR, ADR, ROTATE,
SHIFT, CAST, TSIZE,
(* Internal GM2 compiler functions *)
ShiftVal, ShiftLeft, ShiftRight,
RotateVal, RotateLeft, RotateRight,
THROW, TBITSIZE ;
CONST
(* <implementation-defined constant> ; *)
BITSPERLOC = __ATTRIBUTE__ __BUILTIN__ ((BITS_PER_UNIT)) ;
(* <implementation-defined constant> ; *)
LOCSPERWORD = __ATTRIBUTE__ __BUILTIN__ ((UNITS_PER_WORD)) ;
(* <implementation-defined constant> ; *)
LOCSPERBYTE = 8 DIV BITSPERLOC ;
(*
all the objects below are declared internally to gm2
====================================================
TYPE
LOC ;
ADDRESS ;
BYTE ;
WORD ;
INTEGER8 ;
INTEGER16 ;
INTEGER32 ;
INTEGER64 ;
CARDINAL8 ;
CARDINAL16 ;
CARDINAL32 ;
CARDINAL64 ;
WORD16 ;
WORD32 ;
WORD64 ;
BITSET8 ;
BITSET16 ;
BITSET32 ;
REAL32 ;
REAL64 ;
REAL128 ;
COMPLEX32 ;
COMPLEX64 ;
COMPLEX128 ;
CSIZE_T ;
CSSIZE_T ;
TYPE
LOC; (* A system basic type. Values are the uninterpreted
contents of the smallest addressable unit of storage *)
ADDRESS = POINTER TO LOC;
WORD = ARRAY [0 .. LOCSPERWORD-1] OF LOC;
(* BYTE and LOCSPERBYTE are provided if appropriate for machine *)
TYPE
BYTE = ARRAY [0 .. LOCSPERBYTE-1] OF LOC;
PROCEDURE ADDADR (addr: ADDRESS; offset: CARDINAL): ADDRESS;
(* Returns address given by (addr + offset), or may raise
an exception if this address is not valid.
*)
PROCEDURE SUBADR (addr: ADDRESS; offset: CARDINAL): ADDRESS;
(* Returns address given by (addr - offset), or may raise an
exception if this address is not valid.
*)
PROCEDURE DIFADR (addr1, addr2: ADDRESS): INTEGER;
(* Returns the difference between addresses (addr1 - addr2),
or may raise an exception if the arguments are invalid
or address space is non-contiguous.
*)
PROCEDURE MAKEADR (high: <some type>; ...): ADDRESS;
(* Returns an address constructed from a list of values whose
types are implementation-defined, or may raise an
exception if this address is not valid.
In GNU Modula-2, MAKEADR can take any number of arguments
which are mapped onto the type ADDRESS. The first parameter
maps onto the high address bits and subsequent parameters map
onto lower address bits. For example:
a := MAKEADR(BYTE(0FEH), BYTE(0DCH), BYTE(0BAH), BYTE(098H),
BYTE(076H), BYTE(054H), BYTE(032H), BYTE(010H)) ;
then the value of, a, on a 64 bit machine is: 0FEDCBA9876543210H
The parameters do not have to be the same type, but constants
_must_ be typed.
*)
PROCEDURE ADR (VAR v: <anytype>): ADDRESS;
(* Returns the address of variable v. *)
PROCEDURE ROTATE (val: <a packedset type>;
num: INTEGER): <type of first parameter>;
(* Returns a bit sequence obtained from val by rotating up/right
or down/right by the absolute value of num. The direction is
down/right if the sign of num is negative, otherwise the direction
is up/left.
*)
PROCEDURE SHIFT (val: <a packedset type>;
num: INTEGER): <type of first parameter>;
(* Returns a bit sequence obtained from val by shifting up/left
or down/right by the absolute value of num, introducing
zeros as necessary. The direction is down/right if the sign of
num is negative, otherwise the direction is up/left.
*)
PROCEDURE CAST (<targettype>; val: <anytype>): <targettype>;
(* CAST is a type transfer function. Given the expression
denoted by val, it returns a value of the type <targettype>.
An invalid value for the target value or a
physical address alignment problem may raise an exception.
*)
PROCEDURE TSIZE (<type>; ... ): CARDINAL;
(* Returns the number of LOCS used to store a value of the
specified <type>. The extra parameters, if present,
are used to distinguish variants in a variant record.
*)
PROCEDURE THROW (i: INTEGER) ;
(*
THROW is a GNU extension and was not part of the PIM or ISO
standards. It throws an exception which will be caught by the EXCEPT
block (assuming it exists). This is a compiler builtin function which
interfaces to the GCC exception handling runtime system.
GCC uses the term throw, hence the naming distinction between
the GCC builtin and the Modula-2 runtime library procedure Raise.
The later library procedure Raise will call SYSTEM.THROW after
performing various housekeeping activities.
*)
PROCEDURE TBITSIZE (<type>) : CARDINAL ;
(* Returns the minimum number of bits necessary to represent
<type>. This procedure function is only useful for determining
the number of bits used for any type field within a packed RECORD.
It is not particularly useful elsewhere since <type> might be
optimized for speed, for example a BOOLEAN could occupy a WORD.
*)
*)
(* The following procedures are invoked by GNU Modula-2 to
shift non word set types. They are not part of ISO Modula-2
but are used by GNU Modula-2 to implement the SHIFT procedure
defined above. *)
(*
ShiftVal - is a runtime procedure whose job is to implement
the SHIFT procedure of ISO SYSTEM. GNU Modula-2 will
inline a SHIFT of a single WORD sized set and will only
call this routine for larger sets.
*)
PROCEDURE ShiftVal (VAR s, d: ARRAY OF BITSET;
SetSizeInBits: CARDINAL;
ShiftCount: INTEGER) ;
(*
ShiftLeft - performs the shift left for a multi word set.
This procedure might be called by the back end of
GNU Modula-2 depending whether amount is known at compile
time.
*)
PROCEDURE ShiftLeft (VAR s, d: ARRAY OF BITSET;
SetSizeInBits: CARDINAL;
ShiftCount: CARDINAL) ;
(*
ShiftRight - performs the shift left for a multi word set.
This procedure might be called by the back end of
GNU Modula-2 depending whether amount is known at compile
time.
*)
PROCEDURE ShiftRight (VAR s, d: ARRAY OF BITSET;
SetSizeInBits: CARDINAL;
ShiftCount: CARDINAL) ;
(*
RotateVal - is a runtime procedure whose job is to implement
the ROTATE procedure of ISO SYSTEM. GNU Modula-2 will
inline a ROTATE of a single WORD (or less)
sized set and will only call this routine for larger sets.
*)
PROCEDURE RotateVal (VAR s, d: ARRAY OF BITSET;
SetSizeInBits: CARDINAL;
RotateCount: INTEGER) ;
(*
RotateLeft - performs the rotate left for a multi word set.
This procedure might be called by the back end of
GNU Modula-2 depending whether amount is known at compile
time.
*)
PROCEDURE RotateLeft (VAR s, d: ARRAY OF BITSET;
SetSizeInBits: CARDINAL;
RotateCount: CARDINAL) ;
(*
RotateRight - performs the rotate right for a multi word set.
This procedure might be called by the back end of
GNU Modula-2 depending whether amount is known at compile
time.
*)
PROCEDURE RotateRight (VAR s, d: ARRAY OF BITSET;
SetSizeInBits: CARDINAL;
RotateCount: CARDINAL) ;
END SYSTEM.
The data types CSIZE_T and CSSIZE_T are also exported from the SYSTEM module. The type CSIZE_T is unsigned and is mapped onto the target C data type size_t whereas the type CSSIZE_T is mapped onto the signed C data type ssize_t.
It is anticipated that these should only be used to provide cross platform definition modules for C libraries.
There are also a variety of fixed sized INTEGER and CARDINAL types. The variety of the fixed sized types will depend upon the target architecture.