test: add test for gccgo bug #26248

The fix is CL 122756.

Updates #26248.

Change-Id: Ic4250ab5d01da9f65d0bc033e2306343d9c87a99
Reviewed-on: https://go-review.googlesource.com/122757
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/test/fixedbugs/issue26248.go b/test/fixedbugs/issue26248.go
new file mode 100644 (file)
index 0000000..2f04e48
--- /dev/null
+++ b/test/fixedbugs/issue26248.go
@@ -0,0 +1,39 @@
+// run
+
+// 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 26248: gccgo miscompiles interface field expression.
+// In G().M where G returns an interface, G() is evaluated twice.
+
+package main
+
+type I interface {
+       M()
+}
+
+type T struct{}
+
+func (T) M() {}
+
+var g = 0
+
+//go:noinline
+func G() I {
+       g++
+       return T{}
+}
+
+//go:noinline
+func Use(interface{}) {}
+
+func main() {
+       x := G().M
+       Use(x)
+
+       if g != 1 {
+               println("want 1, got", g)
+               panic("FAIL")
+       }
+}