gc: five bug fixes, one better error.

* check for struct literal assignment to private fields.
* record, fix crash involving parallel map assignment.
* avoid infinite recursion in exportassignok.
* make floating point bounds check precise.
* avoid crash on invalid receiver.

* add context to error about implicit assignment.

Fixes #86.
Fixes #88.
Fixes #158.
Fixes #174.
Fixes #201.
Fixes #204.

R=ken2
https://golang.org/cl/154144

src/cmd/gc/align.c

@@ -495,10 +495,11 @@ typeinit(void)
 	mpatofix(maxintval[TUINT32], "0xffffffff");
 	mpatofix(maxintval[TUINT64], "0xffffffffffffffff");
 
-	mpatoflt(maxfltval[TFLOAT32], "3.40282347e+38");
-	mpatoflt(minfltval[TFLOAT32], "-3.40282347e+38");
-	mpatoflt(maxfltval[TFLOAT64], "1.7976931348623157e+308");
-	mpatoflt(minfltval[TFLOAT64], "-1.7976931348623157e+308");
+	/* f is valid float if min < f < max.  (min and max are not themselves valid.) */
+	mpatoflt(maxfltval[TFLOAT32], "33554431p103");	/* 2^24-1 p (127-23) + 1/2 ulp*/
+	mpatoflt(minfltval[TFLOAT32], "-33554431p103");
+	mpatoflt(maxfltval[TFLOAT64], "18014398509481983p970");	/* 2^53-1 p (1023-52) + 1/2 ulp */
+	mpatoflt(minfltval[TFLOAT64], "-18014398509481983p970");
 
 	/* for walk to use in error messages */
 	types[TFUNC] = functype(N, nil, nil);

src/cmd/gc/const.c

@@ -261,8 +261,8 @@ overflow(Val v, Type *t)
 	case CTFLT:
 		if(!isfloat[t->etype])
 			fatal("overflow: %T floating-point constant", t);
-		if(mpcmpfltflt(v.u.fval, minfltval[t->etype]) < 0
-		|| mpcmpfltflt(v.u.fval, maxfltval[t->etype]) > 0)
+		if(mpcmpfltflt(v.u.fval, minfltval[t->etype]) <= 0
+		|| mpcmpfltflt(v.u.fval, maxfltval[t->etype]) >= 0)
 			yyerror("constant %#F overflows %T", v.u.fval, t);
 		break;
 	}

src/cmd/gc/dcl.c

@@ -302,11 +302,27 @@ NodeList*
 variter(NodeList *vl, Node *t, NodeList *el)
 {
 	int doexpr;
-	Node *v, *e;
+	Node *v, *e, *as2;
 	NodeList *init;
 
 	init = nil;
 	doexpr = el != nil;
+
+	if(count(el) == 1 && count(vl) > 1) {
+		e = el->n;
+		as2 = nod(OAS2, N, N);
+		as2->list = vl;
+		as2->rlist = list1(e);
+		for(; vl; vl=vl->next) {
+			v = vl->n;
+			v->op = ONAME;
+			declare(v, dclcontext);
+			v->ntype = t;
+			v->defn = as2;
+		}
+		return list1(as2);
+	}
+
 	for(; vl; vl=vl->next) {
 		if(doexpr) {
 			if(el == nil) {

src/cmd/gc/go.h

@@ -1048,8 +1048,8 @@ void	typechecklist(NodeList*, int);
 void	typecheckswitch(Node*);
 void	typecheckselect(Node*);
 void	typecheckrange(Node*);
-Node*	typecheckconv(Node*, Node*, Type*, int);
-int	checkconv(Type*, Type*, int, int*, int*);
+Node*	typecheckconv(Node*, Node*, Type*, int, char*);
+int	checkconv(Type*, Type*, int, int*, int*, char*);
 Node*	typecheck(Node**, int);
 
 /*

src/cmd/gc/go.y

@@ -1087,6 +1087,8 @@ xfndcl:
 	LFUNC fndcl fnbody
 	{
 		$$ = $2;
+		if($$ == N)
+			break;
 		$$->nbody = $3;
 		funcbody($$);
 	}
@@ -1111,10 +1113,19 @@ fndcl:
 	{
 		Node *rcvr, *t;
 
+		$$ = N;
+		if($2 == nil) {
+			yyerror("method has no receiver");
+			break;
+		}
+		if($2->next != nil) {
+			yyerror("method has multiple receivers");
+			break;
+		}
 		rcvr = $2->n;
-		if($2->next != nil || $2->n->op != ODCLFIELD) {
+		if(rcvr->op != ODCLFIELD) {
 			yyerror("bad receiver in method");
-			rcvr = N;
+			break;
 		}
 
 		$$ = nod(ODCLFUNC, N, N);

src/cmd/gc/obj.c

@@ -114,6 +114,7 @@ ieeedtod(uint64 *ieee, double native)
 	double fr, ho, f;
 	int exp;
 	uint32 h, l;
+	uint64 bits;
 
 	if(native < 0) {
 		ieeedtod(ieee, -native);
@@ -129,13 +130,20 @@ ieeedtod(uint64 *ieee, double native)
 	fr = modf(fr*f, &ho);
 	h = ho;
 	h &= 0xfffffL;
-	h |= (exp+1022L) << 20;
 	f = 65536L;
 	fr = modf(fr*f, &ho);
 	l = ho;
 	l <<= 16;
 	l |= (int32)(fr*f);
-	*ieee = ((uint64)h << 32) | l;
+	bits = ((uint64)h<<32) | l;
+	if(exp < -1021) {
+		// gradual underflow
+		bits |= 1LL<<52;
+		bits >>= -1021 - exp;
+		exp = -1022;
+	}
+	bits |= (uint64)(exp+1022L) << 52;
+	*ieee = bits;
 }
 
 int

src/cmd/gc/range.c

@@ -66,12 +66,12 @@ typecheckrange(Node *n)
 
 	if(v1->defn == n)
 		v1->type = t1;
-	else if(v1->type != T && checkconv(t1, v1->type, 0, &op, &et) < 0)
+	else if(v1->type != T && checkconv(t1, v1->type, 0, &op, &et, "range") < 0)
 		yyerror("cannot assign type %T to %+N", t1, v1);
 	if(v2) {
 		if(v2->defn == n)
 			v2->type = t2;
-		else if(v2->type != T && checkconv(t2, v2->type, 0, &op, &et) < 0)
+		else if(v2->type != T && checkconv(t2, v2->type, 0, &op, &et, "range") < 0)
 			yyerror("cannot assign type %T to %+N", t1, v1);
 	}
 

src/cmd/gc/sinit.c

@@ -59,6 +59,12 @@ init1(Node *n, NodeList **out)
 				print("%S\n", n->sym);
 			*out = list(*out, n->defn);
 			break;
+
+		case OAS2FUNC:
+			for(l=n->defn->rlist; l; l=l->next)
+				init1(l->n, out);
+			*out = list(*out, n->defn);
+			break;
 		}
 	}
 	n->initorder = 1;