From 924ea515cf1d1a6f5e447c212e00e3e88c785c41 Mon Sep 17 00:00:00 2001
From: Luuk van Dijk <lvd@golang.org>
Date: Wed, 9 Nov 2011 18:30:54 +0100
Subject: [PATCH] gc: better error for non-calling use of unsafe builtins.

Fixes #1951

R=rsc
CC=golang-dev
https://golang.org/cl/5372041
---
 src/cmd/gc/go.h          |  1 +
 src/cmd/gc/typecheck.c   |  4 ++++
 src/cmd/gc/unsafe.c      | 19 +++++++++++++++++--
 test/fixedbugs/bug376.go | 11 +++++++++++
 4 files changed, 33 insertions(+), 2 deletions(-)
 create mode 100644 test/fixedbugs/bug376.go

diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index 52344e75637..faae7bd9eab 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -1247,6 +1247,7 @@ void	queuemethod(Node *n);
 /*
  *	unsafe.c
  */
+int	isunsafebuiltin(Node *n);
 Node*	unsafenmagic(Node *n);
 
 /*
diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index f84f8440c4d..ed5c35ae011 100644
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -210,6 +210,10 @@ reswitch:
 			}
 			n->used = 1;
 		}
+		if(!(top &Ecall) && isunsafebuiltin(n)) {
+			yyerror("%N is not an expression, must be called", n);
+			goto error;
+		}
 		ok |= Erv;
 		goto ret;
 
diff --git a/src/cmd/gc/unsafe.c b/src/cmd/gc/unsafe.c
index 7504b51c994..21496b08cc4 100644
--- a/src/cmd/gc/unsafe.c
+++ b/src/cmd/gc/unsafe.c
@@ -10,6 +10,7 @@
  * look for
  *	unsafe.Sizeof
  *	unsafe.Offsetof
+ *	unsafe.Alignof
  * rewrite with a constant
  */
 Node*
@@ -22,7 +23,7 @@ unsafenmagic(Node *nn)
 	Val val;
 	Node *fn;
 	NodeList *args;
-	
+
 	fn = nn->left;
 	args = nn->list;
 
@@ -83,7 +84,7 @@ bad:
 	yyerror("invalid expression %N", nn);
 	v = 0;
 	goto ret;
-	
+
 yes:
 	if(args->next != nil)
 		yyerror("extra arguments for %S", s);
@@ -97,3 +98,17 @@ ret:
 	n->type = types[TUINTPTR];
 	return n;
 }
+
+int
+isunsafebuiltin(Node *n)
+{
+	if(n == N || n->op != ONAME || n->sym == S || n->sym->pkg != unsafepkg)
+		return 0;
+	if(strcmp(n->sym->name, "Sizeof") == 0)
+		return 1;
+	if(strcmp(n->sym->name, "Offsetof") == 0)
+		return 1;
+	if(strcmp(n->sym->name, "Alignof") == 0)
+		return 1;
+	return 0;
+}
diff --git a/test/fixedbugs/bug376.go b/test/fixedbugs/bug376.go
new file mode 100644
index 00000000000..1efbeecf21c
--- /dev/null
+++ b/test/fixedbugs/bug376.go
@@ -0,0 +1,11 @@
+// errchk $G $D/$F.go
+
+// Copyright 2011 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.
+
+// issue 1951
+package foo
+import "unsafe"
+var v = unsafe.Sizeof  // ERROR "must be called"
+