shithub: scc

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Add lvalue to Node

Some operations (assignment, increment, decrement, take address,
or content) can be only applied to lvalues, so it is important keep track
when a node is a lvalue or not.

--- a/cc.h

+++ b/cc.h

@@ -204,6 +204,9 @@

 typedef struct node {

 	void (*code)(struct node *);

 	Type *type;

+	struct {

+		bool lvalue : 1;

+	} b;

 	union unode {

 		Symbol *sym;

 		Type *type;

--- a/expr.c

+++ b/expr.c

@@ -18,6 +18,7 @@

 		if ((sym = yylval.sym) == NULL)

 			error("'%s' undeclared", yytext);

 		np = node(emitsym, sym->type, SYM(sym), 0);

+		np->b.lvalue = 1;

 		next();

 		break;

 	case CONSTANT:

@@ -50,7 +51,7 @@

 {

 	Node *naux;

 	Type *tp1, *tp2, *tp3;

-	uint8_t t1, t2, taux;

+	uint8_t t1, t2, taux, lvalue = 0;

 	tp1 = UNQUAL(np1->type), tp2 = UNQUAL(np2->type);

 	t1 = tp1->op, t2 = tp2->op;

@@ -101,12 +102,15 @@

 		np2 = bincode(OMUL, tp1,

 		              castcode(np2, tp1),

 		              sizeofcode(tp3));

+		lvalue = 1;

 		break;

 	default:

 		goto incorrect;

 	}

-	return bincode(op, tp1, np1, np2);

+	np1 = bincode(op, tp1, np1, np2);

+	np1->b.lvalue = lvalue;

+	return np1;

 nocomplete:

 	error("invalid use of indefined type");

@@ -145,7 +149,8 @@

 	Type *tp;

 	char *err;

-	/* TODO: Check against l-value */

+	if (!np->b.lvalue)

+		goto nolvalue;

 	tp = UNQUAL(np->type);

 	if (isconst(np->type->op))

 		goto const_mod;

@@ -155,11 +160,16 @@

 		if (!tp->type->defined)

 			goto nocomplete;

 	case INT: case FLOAT:

-		return unarycode(op, np->type, np);

+		np = unarycode(op, np->type, np);

+		np->b.lvalue = 0;

+		return np;

 	default:

 		goto bad_type;

 	}

+nolvalue:

+	err = "lvalue required in operation";

+	goto error;

 nocomplete:

 	err = "invalid use of indefined type";

 	goto error;