[release-branch.go1.10] cmd/cgo: don't give inconsistent typedef error for cgo-defined types

The cgo tool predefines some C types such as C.uint. Don't give an
error if the type that cgo defines does not match the type in a header file.

Fixes #26743

Change-Id: I9ed3b4c482b558d8ffa8bf61eb3209415b7a9e3c
Reviewed-on: https://go-review.googlesource.com/127356
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
(cherry picked from commit c29370c98ecfc7aa59f32c7a7897e50a0f6eb86b)
Reviewed-on: https://go-review.googlesource.com/128396
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

4 files changed, 34 insertions, 0 deletions

diff --git a/misc/cgo/test/issue26743.go b/misc/cgo/test/issue26743.go
new file mode 100644
index 0000000000..35c8473a61
--- /dev/null
+++ b/misc/cgo/test/issue26743.go
@@ -0,0 +1,10 @@
+// Copyright 2018 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 26743: typedef of uint leads to inconsistent typedefs error.
+// No runtime test; just make sure it compiles.
+
+package cgotest
+
+import _ "./issue26743"
diff --git a/misc/cgo/test/issue26743/a.go b/misc/cgo/test/issue26743/a.go
new file mode 100644
index 0000000000..a3df1797b3
--- /dev/null
+++ b/misc/cgo/test/issue26743/a.go
@@ -0,0 +1,11 @@
+// Copyright 2018 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 issue26743
+
+// typedef unsigned int uint;
+// int C1(uint x) { return x; }
+import "C"
+
+var V1 = C.C1(0)
diff --git a/misc/cgo/test/issue26743/b.go b/misc/cgo/test/issue26743/b.go
new file mode 100644
index 0000000000..c5f1ae478c
--- /dev/null
+++ b/misc/cgo/test/issue26743/b.go
@@ -0,0 +1,9 @@
+// Copyright 2018 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 issue26743
+
+import "C"
+
+var V2 C.uint
diff --git a/src/cmd/cgo/main.go b/src/cmd/cgo/main.go
index 2b3e6a0a01..c3c53b35c0 100644
--- a/src/cmd/cgo/main.go
+++ b/src/cmd/cgo/main.go
@@ -394,6 +394,10 @@ func (p *Package) Record(f *File) {
 				p.Name[k] = v
 			} else if p.incompleteTypedef(v.Type) {
 				// Nothing to do.
+			} else if _, ok := nameToC[k]; ok {
+				// Names we predefine may appear inconsistent
+				// if some files typedef them and some don't.
+				// Issue 26743.
 			} else if !reflect.DeepEqual(p.Name[k], v) {
 				error_(token.NoPos, "inconsistent definitions for C.%s", fixGo(k))
 			}