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C-- Specification

EECS 483 Compiler Construction
Fall 2004
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C-- is a subset of the C programming language.  Thus for anything not
specified below, you can assume standard ansi C syntax.  Most of the
major constructs are present, but there are also many limitations.


==Preprocessor Macros==

No macros are allowed in C--.  This
precludes the use of #includes, thus all library functions must be
extern-defined with the return type specified.

==Primitives==

The only primitives are integers, characters, void and their pointers.
Pointers in C-- allow for only ONE level of indirection.  Thus, one
would never see:

	char **my_var;

There are no floating-point or double-precision floating-point
primitives.


==Constants==

The only allowed constants in C-- are integers and double-quoted
strings.  Please note that single-quoted characters are NOT allowed.
Note also that your lexer should support multi-line string constants.


==Keywords==

C-- recognizes ONLY the following keywords:
int	char	void	if	else	for	while
extern	return

The following reserved words are NOT VALID in C--:
auto	break	case	default	do	double	volatile
entry	float	goto	long	short	sizeof	register
struct	switch	typedef	union	enum	const	unsigned
static	continue

Note that the above listing implies the absence of constructs such
as switch statement and structs in C--.


==Braces in Conditionals & Loops==

In addition, all conditionals and loops must have followed by a set
of braces.  This means that while

	if(a > 0)
	{
		printf("Hello world\n");
	}

is valid,

	if(a > 0)
		printf("Hellow world\n");

is not.

The short-circuit operators (? :) are not used in C--.


==Declarations==

C-- also forbids multiple variable declarations in the same
statement.  Thus

	int a;
	int b;

is valid, while

	int a, b;

is not recognized.  Initialization is also prohibited in a variable
declaration.  Thus,

	int a = 0;

is not recognized.

Arrays may only be initialized in one dimension and can only have their
sizes specified using a single integer constants.  For example:

	int a[30];

All function prototypes and extern defines must be ansi style.  That is,
a prototype must be of the form

	int foo(int x, int y, ...);

and an extern defined function of the form

	extern char bar(int a, char z,...);

You MUST support var args in your grammar.


==Assignments==

Once again, assignments are forbidden in variable declarations.  Furthermore,
C-- does not allow multiple assignments in the same statement.  Thus,

	a = 4, b = 3;

is NOT a valid C-- statement.

While individual array elements can be accessed, an array may not be instantiated
by giving a list of elements in braces.  That is, the following is not allowed:

	int a[3] = {4, 5, 6};


==Return Statements==

Just as a reminder, C-- should recognize return statements with and without values.

e.g.

return 0; and
return;


==Operators==

The bit-wise operators are not supported in C--. That means no | & ^