cmd/link: support -X values for main.* in plugins

Fixes #19418

Change-Id: I98205f40c1915cd68a5d20438469ba06f1efb160
Reviewed-on: https://go-review.googlesource.com/67432
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, 41 insertions, 0 deletions

diff --git a/misc/cgo/testplugin/src/issue19418/main.go b/misc/cgo/testplugin/src/issue19418/main.go
new file mode 100644
index 0000000000..2ec9f9aaaa
--- /dev/null
+++ b/misc/cgo/testplugin/src/issue19418/main.go
@@ -0,0 +1,29 @@
+// 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
+
+import (
+	"fmt"
+	"os"
+	"plugin"
+)
+
+func main() {
+	p, err := plugin.Open("plugin.so")
+	if err != nil {
+		panic(err)
+	}
+
+	val, err := p.Lookup("Val")
+	if err != nil {
+		panic(err)
+	}
+	got := *val.(*string)
+	const want = "linkstr"
+	if got != want {
+		fmt.Fprintf(os.Stderr, "issue19418 value is %q, want %q\n", got, want)
+		os.Exit(2)
+	}
+}
diff --git a/misc/cgo/testplugin/src/issue19418/plugin.go b/misc/cgo/testplugin/src/issue19418/plugin.go
new file mode 100644
index 0000000000..fe93b16143
--- /dev/null
+++ b/misc/cgo/testplugin/src/issue19418/plugin.go
@@ -0,0 +1,7 @@
+// 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 Val = "val-unset"
diff --git a/misc/cgo/testplugin/test.bash b/misc/cgo/testplugin/test.bash
index a52aa46037..ae3368b45f 100755
--- a/misc/cgo/testplugin/test.bash
+++ b/misc/cgo/testplugin/test.bash
@@ -66,3 +66,8 @@ GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -o issue19534 src/issue19534/main.
 GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -buildmode=plugin -o plugin.so src/issue18584/plugin.go
 GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -o issue18584 src/issue18584/main.go
 ./issue18584
+
+# Test for issue 19418
+GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -buildmode=plugin "-ldflags=-X main.Val=linkstr" -o plugin.so src/issue19418/plugin.go
+GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -o issue19418 src/issue19418/main.go
+./issue19418