dcl.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include "cc.h"

Node*
dodecl(void (*f)(int,Type*,Sym*), int c, Type *t, Node *n)
{
	Sym *s;
	Node *n1;
	long v;

	nearln = lineno;
	lastfield = 0;

loop:
	if(n != Z)
	switch(n->op) {
	default:
		diag(n, "unknown declarator: %O", n->op);
		break;

	case OARRAY:
		t = typ(TARRAY, t);
		t->width = 0;
		n1 = n->right;
		n = n->left;
		if(n1 != Z) {
			complex(n1);
			v = -1;
			if(n1->op == OCONST)
				v = n1->vconst;
			if(v <= 0) {
				diag(n, "array size must be a positive constant");
				v = 1;
			}
			t->width = v * t->link->width;
		}
		goto loop;

	case OIND:
		t = typ(TIND, t);
		t->garb = n->garb;
		n = n->left;
		goto loop;

	case OFUNC:
		t = typ(TFUNC, t);
		t->down = fnproto(n);
		n = n->left;
		goto loop;

	case OBIT:
		n1 = n->right;
		complex(n1);
		lastfield = -1;
		if(n1->op == OCONST)
			lastfield = n1->vconst;
		if(lastfield < 0) {
			diag(n, "field width must be non-negative constant");
			lastfield = 1;
		}
		if(lastfield == 0) {
			lastbit = 0;
			firstbit = 1;
			if(n->left != Z) {
				diag(n, "zero width named field");
				lastfield = 1;
			}
		}
		if(!typei[t->etype]) {
			diag(n, "field type must be int-like");
			t = types[TINT];
			lastfield = 1;
		}
		if(lastfield > tfield->width*8) {
			diag(n, "field width larger than field unit");
			lastfield = 1;
		}
		lastbit += lastfield;
		if(lastbit > tfield->width*8) {
			lastbit = lastfield;
			firstbit = 1;
		}
		n = n->left;
		goto loop;

	case ONAME:
		if(f == NODECL)
			break;
		s = n->sym;
		(*f)(c, t, s);
		if(s->class == CLOCAL)
			s = mkstatic(s);
		firstbit = 0;
		n->sym = s;
		n->type = s->type;
		n->xoffset = s->offset;
		n->class = s->class;
		n->etype = TVOID;
		if(n->type != T)
			n->etype = n->type->etype;
		if(debug['d'])
			dbgdecl(s);
		acidvar(s);
		s->varlineno = lineno;
		break;
	}
	lastdcl = t;
	return n;
}

Sym*
mkstatic(Sym *s)
{
	Sym *s1;

	if(s->class != CLOCAL)
		return s;
	snprint(symb, NSYMB, "%s$%d", s->name, s->block);
	s1 = lookup();
	if(s1->class != CSTATIC) {
		s1->type = s->type;
		s1->offset = s->offset;
		s1->block = s->block;
		s1->class = CSTATIC;
	}
	return s1;
}

/*
 * make a copy of a typedef
 * the problem is to split out incomplete
 * arrays so that it is in the variable
 * rather than the typedef.
 */
Type*
tcopy(Type *t)
{
	Type *tl, *tx;
	int et;

	if(t == T)
		return t;
	et = t->etype;
	if(typesu[et])
		return t;
	tl = tcopy(t->link);
	if(tl != t->link ||
	  (et == TARRAY && t->width == 0)) {
		tx = copytyp(t);
		tx->link = tl;
		return tx;
	}
	return t;
}

Node*
doinit(Sym *s, Type *t, long o, Node *a)
{
	Node *n;

	if(t == T)
		return Z;
	if(s->class == CEXTERN) {
		s->class = CGLOBL;
		if(debug['d'])
			dbgdecl(s);
	}
	if(debug['i']) {
		print("t = %T; o = %ld; n = %s\n", t, o, s->name);
		prtree(a, "doinit value");
	}


	n = initlist;
	if(a->op == OINIT)
		a = a->left;
	initlist = a;

	a = init1(s, t, o, 0);
	if(initlist != Z)
		diag(initlist, "more initializers than structure: %s",
			s->name);
	initlist = n;

	return a;
}

/*
 * get next major operator,
 * dont advance initlist.
 */
Node*
peekinit(void)
{
	Node *a;

	a = initlist;

loop:
	if(a == Z)
		return a;
	if(a->op == OLIST) {
		a = a->left;
		goto loop;
	}
	return a;
}

/*
 * consume and return next element on
 * initlist. expand strings.
 */
Node*
nextinit(void)
{
	Node *a, *b, *n;

	a = initlist;
	n = Z;

	if(a == Z)
		return a;
	if(a->op == OLIST) {
		n = a->right;
		a = a->left;
	}
	if(a->op == OUSED) {
		a = a->left;
		b = new(OCONST, Z, Z);
		b->type = a->type->link;
		if(a->op == OSTRING) {
			b->vconst = convvtox(*a->cstring, TCHAR);
			a->cstring++;
		}
		if(a->op == OLSTRING) {
			b->vconst = convvtox(*a->rstring, TUSHORT);
			a->rstring++;
		}
		a->type->width -= b->type->width;
		if(a->type->width <= 0)
			initlist = n;
		return b;
	}
	initlist = n;
	return a;
}

int
isstruct(Node *a, Type *t)
{
	Node *n;

	switch(a->op) {
	case ODOTDOT:
		n = a->left;
		if(n && n->type && sametype(n->type, t))
			return 1;
	case OSTRING:
	case OLSTRING:
	case OCONST:
	case OINIT:
	case OELEM:
		return 0;
	}

	n = new(ODOTDOT, Z, Z);
	*n = *a;

	/*
	 * ODOTDOT is a flag for tcom
	 * a second tcom will not be performed
	 */
	a->op = ODOTDOT;
	a->left = n;
	a->right = Z;

	if(tcom(n))
		return 0;

	if(sametype(n->type, t))
		return 1;
	return 0;
}

Node*
init1(Sym *s, Type *t, long o, int exflag)
{
	Node *a, *l, *r, nod;
	Type *t1;
	long e, w, so, mw;

	a = peekinit();
	if(a == Z)
		return Z;

	if(debug['i']) {
		print("t = %T; o = %ld; n = %s\n", t, o, s->name);
		prtree(a, "init1 value");
	}

	if(exflag && a->op == OINIT)
		return doinit(s, t, o, nextinit());

	switch(t->etype) {
	default:
		diag(Z, "unknown type in initialization: %T to: %s", t, s->name);
		return Z;

	case TCHAR:
	case TUCHAR:
	case TINT:
	case TUINT:
	case TSHORT:
	case TUSHORT:
	case TLONG:
	case TULONG:
	case TVLONG:
	case TUVLONG:
	case TFLOAT:
	case TDOUBLE:
	case TIND:
	single:
		if(a->op == OARRAY || a->op == OELEM)
			return Z;

		a = nextinit();
		if(a == Z)
			return Z;

		if(t->nbits)
			diag(Z, "cannot initialize bitfields");
		if(s->class == CAUTO) {
			l = new(ONAME, Z, Z);
			l->sym = s;
			l->type = t;
			l->etype = TVOID;
			if(s->type)
				l->etype = s->type->etype;
			l->xoffset = s->offset + o;
			l->class = s->class;

			l = new(OASI, l, a);
			return l;
		}

		complex(a);
		if(a->type == T)
			return Z;

		if(a->op == OCONST) {
			if(vconst(a) && t->etype == TIND && a->type && a->type->etype != TIND){
				diag(a, "initialize pointer to an integer: %s", s->name);
				return Z;
			}
			if(!sametype(a->type, t)) {
				/* hoop jumping to save malloc */
				if(nodcast == Z)
					nodcast = new(OCAST, Z, Z);
				nod = *nodcast;
				nod.left = a;
				nod.type = t;
				nod.lineno = a->lineno;
				complex(&nod);
				if(nod.type)
					*a = nod;
			}
			if(a->op != OCONST) {
				diag(a, "initializer is not a constant: %s",
					s->name);
				return Z;
			}
			if(vconst(a) == 0)
				return Z;
			goto gext;
		}
		if(t->etype == TIND) {
			while(a->op == OCAST) {
				warn(a, "CAST in initialization ignored");
				a = a->left;
			}
			if(!sametype(t, a->type)) {
				diag(a, "initialization of incompatible pointers: %s\n%T and %T",
					s->name, t, a->type);
			}
			if(a->op == OADDR)
				a = a->left;
			goto gext;
		}

		while(a->op == OCAST)
			a = a->left;
		if(a->op == OADDR) {
			warn(a, "initialize pointer to an integer: %s", s->name);
			a = a->left;
			goto gext;
		}
		diag(a, "initializer is not a constant: %s", s->name);
		return Z;

	gext:
		gextern(s, a, o, t->width);

		return Z;

	case TARRAY:
		w = t->link->width;
		if(a->op == OSTRING || a->op == OLSTRING)
		if(typei[t->link->etype]) {
			/*
			 * get rid of null if sizes match exactly
			 */
			a = nextinit();
			mw = t->width/w;
			so = a->type->width/a->type->link->width;
			if(mw && so > mw) {
				if(so != mw+1)
					diag(a, "string initialization larger than array");
				a->type->width -= a->type->link->width;
			}

			/*
			 * arrange strings to be expanded
			 * inside OINIT braces.
			 */
			a = new(OUSED, a, Z);
			return doinit(s, t, o, a);
		}

		mw = -w;
		l = Z;
		for(e=0;;) {
			/*
			 * peek ahead for element initializer
			 */
			a = peekinit();
			if(a == Z)
				break;
			if(a->op == OELEM && t->link->etype != TSTRUCT)
				break;
			if(a->op == OARRAY) {
				if(e && exflag)
					break;
				a = nextinit();
				r = a->left;
				complex(r);
				if(r->op != OCONST) {
					diag(r, "initializer subscript must be constant");
					return Z;
				}
				e = r->vconst;
				if(t->width != 0)
					if(e < 0 || e*w >= t->width) {
						diag(a, "initialization index out of range: %ld", e);
						continue;
					}
			}

			so = e*w;
			if(so > mw)
				mw = so;
			if(t->width != 0)
				if(mw >= t->width)
					break;
			r = init1(s, t->link, o+so, 1);
			l = newlist(l, r);
			e++;
		}
		if(t->width == 0)
			t->width = mw+w;
		return l;

	case TUNION:
	case TSTRUCT:
		/*
		 * peek ahead to find type of rhs.
		 * if its a structure, then treat
		 * this element as a variable
		 * rather than an aggregate.
		 */
		if(isstruct(a, t))
			goto single;

		if(t->width <= 0) {
			diag(Z, "incomplete structure: %s", s->name);
			return Z;
		}
		l = Z;

	again:
		for(t1 = t->link; t1 != T; t1 = t1->down) {
			if(a->op == OARRAY && t1->etype != TARRAY)
				break;
			if(a->op == OELEM) {
				if(t1->sym != a->sym)
					continue;
				nextinit();
			}
			r = init1(s, t1, o+t1->offset, 1);
			l = newlist(l, r);
			a = peekinit();
			if(a == Z)
				break;
			if(a->op == OELEM)
				goto again;
		}
		if(a && a->op == OELEM)
			diag(a, "structure element not found %F", a);
		return l;
	}
}

Node*
newlist(Node *l, Node *r)
{
	if(r == Z)
		return l;
	if(l == Z)
		return r;
	return new(OLIST, l, r);
}

void
suallign(Type *t)
{
	Type *l;
	long o, w;

	o = 0;
	switch(t->etype) {

	case TSTRUCT:
		t->offset = 0;
		w = 0;
		for(l = t->link; l != T; l = l->down) {
			if(l->nbits) {
				if(l->shift <= 0) {
					l->shift = -l->shift;
					w = round(w, tfield->width);
					o = w;
					w += tfield->width;
				}
				l->offset = o;
			} else {
				if(l->width <= 0)
				if(l->down != T)
					if(l->sym)
						diag(Z, "incomplete structure element: %s",
							l->sym->name);
					else
						diag(Z, "incomplete structure element");
				w = align(w, l, Ael1);
				l->offset = w;
				w = align(w, l, Ael2);
			}
		}
		w = align(w, t, Asu2);
		t->width = w;
		acidtype(t);
		pickletype(t);
		return;

	case TUNION:
		t->offset = 0;
		w = 0;
		for(l = t->link; l != T; l = l->down) {
			if(l->width <= 0)
				if(l->sym)
					diag(Z, "incomplete union element: %s",
						l->sym->name);
				else
					diag(Z, "incomplete union element");
			l->offset = 0;
			l->shift = 0;
			o = align(align(0, l, Ael1), l, Ael2);
			if(o > w)
				w = o;
		}
		w = align(w, t, Asu2);
		t->width = w;
		acidtype(t);
		pickletype(t);
		return;

	default:
		diag(Z, "unknown type in suallign: %T", t);
		break;
	}
}

long
round(long v, int w)
{
	int r;

	if(w <= 0 || w > 8) {
		diag(Z, "rounding by %d", w);
		w = 1;
	}
	r = v%w;
	if(r)
		v += w-r;
	return v;
}

Type*
ofnproto(Node *n)
{
	Type *tl, *tr, *t;

	if(n == Z)
		return T;
	switch(n->op) {
	case OLIST:
		tl = ofnproto(n->left);
		tr = ofnproto(n->right);
		if(tl == T)
			return tr;
		tl->down = tr;
		return tl;

	case ONAME:
		t = copytyp(n->sym->type);
		t->down = T;
		return t;
	}
	return T;
}

#define	ANSIPROTO	1
#define	OLDPROTO	2

void
argmark(Node *n, int pass)
{
	Type *t;

	autoffset = align(0, thisfn->link, Aarg0);
	stkoff = 0;
	for(; n->left != Z; n = n->left) {
		if(n->op != OFUNC || n->left->op != ONAME)
			continue;
		walkparam(n->right, pass);
		if(pass != 0 && anyproto(n->right) == OLDPROTO) {
			t = typ(TFUNC, n->left->sym->type->link);
			t->down = typ(TOLD, T);
			t->down->down = ofnproto(n->right);
			tmerge(t, n->left->sym);
			n->left->sym->type = t;
		}
		break;
	}
	autoffset = 0;
	stkoff = 0;
}

void
walkparam(Node *n, int pass)
{
	Sym *s;
	Node *n1;

	if(n != Z && n->op == OPROTO && n->left == Z && n->type == types[TVOID])
		return;

loop:
	if(n == Z)
		return;
	switch(n->op) {
	default:
		diag(n, "argument not a name/prototype: %O", n->op);
		break;

	case OLIST:
		walkparam(n->left, pass);
		n = n->right;
		goto loop;

	case OPROTO:
		for(n1 = n; n1 != Z; n1=n1->left)
			if(n1->op == ONAME) {
				if(pass == 0) {
					s = n1->sym;
					push1(s);
					s->offset = -1;
					break;
				}
				dodecl(pdecl, CPARAM, n->type, n->left);
				break;
			}
		if(n1)
			break;
		if(pass == 0) {
			/*
			 * extension:
			 *	allow no name in argument declaration
			diag(Z, "no name in argument declaration");
			 */
			break;
		}
		dodecl(NODECL, CPARAM, n->type, n->left);
		pdecl(CPARAM, lastdcl, S);
		break;

	case ODOTDOT:
		break;
	
	case ONAME:
		s = n->sym;
		if(pass == 0) {
			push1(s);
			s->offset = -1;
			break;
		}
		if(s->offset != -1) {
			if(autoffset == 0) {
				firstarg = s;
				firstargtype = s->type;
			}
			autoffset = align(autoffset, s->type, Aarg1);
			s->offset = autoffset;
			autoffset = align(autoffset, s->type, Aarg2);
		} else
			dodecl(pdecl, CXXX, types[TINT], n);
		break;
	}
}

void
markdcl(void)
{
	Decl *d;

	blockno++;
	d = push();
	d->val = DMARK;
	d->offset = autoffset;
	d->block = autobn;
	autobn = blockno;
}

Node*
revertdcl(void)
{
	Decl *d;
	Sym *s;
	Node *n, *n1;

	n = Z;
	for(;;) {
		d = dclstack;
		if(d == D) {
			diag(Z, "pop off dcl stack");
			break;
		}
		dclstack = d->link;
		s = d->sym;
		switch(d->val) {
		case DMARK:
			autoffset = d->offset;
			autobn = d->block;
			return n;

		case DAUTO:
			if(debug['d'])
				print("revert1 \"%s\"\n", s->name);
			if(s->aused == 0) {
				nearln = s->varlineno;
				if(s->class == CAUTO)
					warn(Z, "auto declared and not used: %s", s->name);
				if(s->class == CPARAM)
					warn(Z, "param declared and not used: %s", s->name);
			}
			if(s->type && (s->type->garb & GVOLATILE)) {
				n1 = new(ONAME, Z, Z);
				n1->sym = s;
				n1->type = s->type;
				n1->etype = TVOID;
				if(n1->type != T)
					n1->etype = n1->type->etype;
				n1->xoffset = s->offset;
				n1->class = s->class;

				n1 = new(OADDR, n1, Z);
				n1 = new(OUSED, n1, Z);
				if(n == Z)
					n = n1;
				else
					n = new(OLIST, n1, n);
			}
			s->type = d->type;
			s->class = d->class;
			s->offset = d->offset;
			s->block = d->block;
			s->varlineno = d->varlineno;
			s->aused = d->aused;
			break;

		case DSUE:
			if(debug['d'])
				print("revert2 \"%s\"\n", s->name);
			s->suetag = d->type;
			s->sueblock = d->block;
			break;

		case DLABEL:
			if(debug['d'])
				print("revert3 \"%s\"\n", s->name);
			if(s->label && s->label->addable == 0)
				warn(s->label, "label declared and not used \"%s\"", s->name);
			s->label = Z;
			break;
		}
	}
	return n;
}

Type*
fnproto(Node *n)
{