cmd/cgo: do not rewrite call if there are more args than parameters

We already skipped rewriting the call if there were fewer args than
parameters. But we can also get a cgo crash if there are more args,
if at least one of the extra args uses a name qualified with "C.".
Skip the rewrite, since the build will fail later anyhow.

Fixes #33061

Change-Id: I62ff3518b775b502ad10c2bacf9102db4c9a531c
Reviewed-on: https://go-review.googlesource.com/c/go/+/185797
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Bonventre <andybons@golang.org>

3 files changed, 21 insertions, 3 deletions

diff --git a/misc/cgo/errors/errors_test.go b/misc/cgo/errors/errors_test.go
index e6bac0fff4..1bdf843451 100644
--- a/misc/cgo/errors/errors_test.go
+++ b/misc/cgo/errors/errors_test.go
@@ -112,6 +112,7 @@ func TestReportsTypeErrors(t *testing.T) {
 		"issue18452.go",
 		"issue18889.go",
 		"issue28721.go",
+		"issue33061.go",
 	} {
 		check(t, file)
 	}
diff --git a/misc/cgo/errors/testdata/issue33061.go b/misc/cgo/errors/testdata/issue33061.go
new file mode 100644
index 0000000000..77d5f7a7c9
--- /dev/null
+++ b/misc/cgo/errors/testdata/issue33061.go
@@ -0,0 +1,17 @@
+// Copyright 2019 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.
+
+// cgo shouldn't crash if there is an extra argument with a C reference.
+
+package main
+
+// void F(void* p) {};
+import "C"
+
+import "unsafe"
+
+func F() {
+	var i int
+	C.F(unsafe.Pointer(&i), C.int(0)) // ERROR HERE
+}
diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index 1bd3e2417c..01b86adadb 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -793,10 +793,10 @@ func (p *Package) rewriteCall(f *File, call *Call) (string, bool) {
 	params := name.FuncType.Params
 	args := call.Call.Args
 
-	// Avoid a crash if the number of arguments is
-	// less than the number of parameters.
+	// Avoid a crash if the number of arguments doesn't match
+	// the number of parameters.
 	// This will be caught when the generated file is compiled.
-	if len(args) < len(params) {
+	if len(args) != len(params) {
 		return "", false
 	}