gc: diagnose invalid array bounds

Fixes #587.

R=ken2
CC=golang-dev
https://golang.org/cl/207085

src/cmd/gc/const.c

@@ -6,9 +6,7 @@
 #define	TUP(x,y)	(((x)<<16)|(y))
 
 static Val toflt(Val);
-static Val toint(Val);
 static Val tostr(Val);
-static void overflow(Val, Type*);
 static Val copyval(Val);
 
 /*
@@ -236,7 +234,7 @@ toflt(Val v)
 	return v;
 }
 
-static Val
+Val
 toint(Val v)
 {
 	Mpint *i;
@@ -251,7 +249,7 @@ toint(Val v)
 	return v;
 }
 
-static void
+void
 overflow(Val v, Type *t)
 {
 	// v has already been converted

src/cmd/gc/go.h

@@ -1088,6 +1088,8 @@ int	consttype(Node*);
 int	isconst(Node*, int);
 Mpflt*	truncfltlit(Mpflt*, Type*);
 void	convconst(Node*, Type*, Val*);
+Val	toint(Val);
+void	overflow(Val, Type*);
 
 /*
  *	align.c

src/cmd/gc/typecheck.c

@@ -51,9 +51,10 @@ typecheck(Node **np, int top)
 	int et, op;
 	Node *n, *l, *r;
 	NodeList *args;
-	int lno, ok, ntop;
+	int lno, ok, ntop, ct;
 	Type *t;
 	Sym *sym;
+	Val v;
 
 	// cannot type check until all the source has been parsed
 	if(!typecheckok)
@@ -157,29 +158,28 @@ reswitch:
 		l = n->left;
 		r = n->right;
 		if(l == nil) {
-			t->bound = -1;
+			t->bound = -1;	// slice
+		} else if(l->op == ODDD) {
+			t->bound = -100;	// to be filled in
 		} else {
-			if(l->op != ODDD)
-				typecheck(&l, Erv | Etype);
-			switch(l->op) {
+			l = typecheck(&n->left, Erv);
+			switch(consttype(l)) {
+			case CTINT:
+				v = l->val;
+				break;
+			case CTFLT:
+				v = toint(l->val);
+				break;
 			default:
 				yyerror("invalid array bound %#N", l);
 				goto error;
-
-			case OLITERAL:
-				if(consttype(l) == CTINT) {
-					t->bound = mpgetfix(l->val.u.xval);
-					if(t->bound < 0) {
-						yyerror("array bound must be non-negative");
-						goto error;
-					}
-				}
-				break;
-
-			case ODDD:
-				t->bound = -100;
-				break;
 			}
+			t->bound = mpgetfix(v.u.xval);
+			if(t->bound < 0) {
+				yyerror("array bound must be non-negative");
+				goto error;
+			} else
+				overflow(v, types[TINT]);
 		}
 		typecheck(&r, Etype);
 		if(r->type == T)

test/fixedbugs/bug254.go

+// $G $D/$F.go && $L $F.$A && ./$A.out || echo BUG: bug254
+
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+var a [10]int
+var b [1e1]int
+
+func main() {
+	if len(a) != 10 || len(b) != 10 {
+		panicln("len", len(a), len(b))
+	}
+}

test/fixedbugs/bug255.go

+// errchk $G -e $D/$F.go
+
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+var a [10]int	// ok
+var b [1e1]int	// ok
+var c [1.5]int	// ERROR "truncated"
+var d ["abc"]int	// ERROR "invalid array bound"
+var e [nil]int	// ERROR "invalid array bound"
+var f [e]int	// ERROR "invalid array bound"
+var g [1<<65]int	// ERROR "overflows"