cmd/link, plugin: always encode path

Both the linker and the plugin package were inconsistent
about when they applied the path encoding defined in
objabi.PathToPrefix. As a result, only some symbols from
a package path that required encoding were being found.

So always encoding the path.

Fixes #22295

Change-Id: Ife86c79ca20b2e9307008ed83885e193d32b7dc4
Reviewed-on: https://go-review.googlesource.com/72390
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

3 files changed, 49 insertions, 0 deletions

diff --git a/misc/cgo/testplugin/src/issue22295.pkg/main.go b/misc/cgo/testplugin/src/issue22295.pkg/main.go
new file mode 100644
index 0000000000..6cb186e100
--- /dev/null
+++ b/misc/cgo/testplugin/src/issue22295.pkg/main.go
@@ -0,0 +1,28 @@
+// Copyright 2017 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.
+
+// +build ignore
+
+package main
+
+import (
+	"log"
+	"plugin"
+)
+
+func main() {
+	p, err := plugin.Open("issue.22295.so")
+	if err != nil {
+		log.Fatal(err)
+	}
+	f, err := p.Lookup("F")
+	if err != nil {
+		log.Fatal(err)
+	}
+	const want = 2503
+	got := f.(func() int)()
+	if got != want {
+		log.Fatalf("got %d, want %d", got, want)
+	}
+}
diff --git a/misc/cgo/testplugin/src/issue22295.pkg/plugin.go b/misc/cgo/testplugin/src/issue22295.pkg/plugin.go
new file mode 100644
index 0000000000..46b08a405b
--- /dev/null
+++ b/misc/cgo/testplugin/src/issue22295.pkg/plugin.go
@@ -0,0 +1,16 @@
+// Copyright 2017 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 f *int
+
+func init() {
+	f = new(int)
+	*f = 2503
+}
+
+func F() int { return *f }
+
+func main() {}
diff --git a/misc/cgo/testplugin/test.bash b/misc/cgo/testplugin/test.bash
index eed7fc451b..18e3803bf4 100755
--- a/misc/cgo/testplugin/test.bash
+++ b/misc/cgo/testplugin/test.bash
@@ -80,3 +80,8 @@ GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -buildmode=plugin -o issue22175_pl
 GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -buildmode=plugin -o issue22175_plugin2.so src/issue22175/plugin2.go
 GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -o issue22175 src/issue22175/main.go
 ./issue22175
+
+# Test for issue 22295
+GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -buildmode=plugin -o issue.22295.so issue22295.pkg
+GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -o issue22295 src/issue22295.pkg/main.go
+./issue22295