cmd/cgo: error, not panic, if not enough arguments to function

Fixes #16116.

Change-Id: Ic3cb0b95382bb683368743bda49b4eb5fdcc35c0
Reviewed-on: https://go-review.googlesource.com/24286
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

misc/cgo/errors/issue16116.go

@@ -0,0 +1,12 @@
+// Copyright 2016 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
+
+// void f(void *p, int x) {}
+import "C"
+
+func main() {
+	_ = C.f(1) // ERROR HERE
+}

misc/cgo/errors/test.bash

@@ -45,6 +45,7 @@ expect issue13129.go C.ushort
 check issue13423.go
 expect issue13635.go C.uchar C.schar C.ushort C.uint C.ulong C.longlong C.ulonglong C.complexfloat C.complexdouble
 check issue13830.go
+check issue16116.go
 
 if ! go build issue14669.go; then
 	exit 1

src/cmd/cgo/gcc.go

@@ -597,13 +597,15 @@ func (p *Package) rewriteCalls(f *File) {
 // rewriteCall rewrites one call to add pointer checks. We replace
 // each pointer argument x with _cgoCheckPointer(x).(T).
 func (p *Package) rewriteCall(f *File, call *Call, name *Name) {
+	// Avoid a crash if the number of arguments is
+	// less than the number of parameters.
+	// This will be caught when the generated file is compiled.
+	if len(call.Call.Args) < len(name.FuncType.Params) {
+		return
+	}
+
 	any := false
 	for i, param := range name.FuncType.Params {
-		if len(call.Call.Args) <= i {
-			// Avoid a crash; this will be caught when the
-			// generated file is compiled.
-			return
-		}
 		if p.needsPointerCheck(f, param.Go, call.Call.Args[i]) {
 			any = true
 			break