cmd/cgo: use first error position instead of last one

Just like https://golang.org/cl/34783

Given cgo.go:
     1	package main
     2
     3	/*
     4	long double x = 0;
     5	*/
     6	import "C"
     7
     8	func main() {
     9		_ = C.x
    10		_ = C.x
    11	}

Before:
    ./cgo.go:10:6: unexpected: 16-byte float type - long double

After:
    ./cgo.go:9:6: unexpected: 16-byte float type - long double

The above test case is not portable. So it is tested on only amd64.

Change-Id: If0b84cf73d381a22e2ada71c8e9a6e6ec77ffd2e
Reviewed-on: https://go-review.googlesource.com/54950
Reviewed-by: Ian Lance Taylor <iant@golang.org>

2 files changed, 18 insertions, 0 deletions

diff --git a/misc/cgo/errors/err4.go b/misc/cgo/errors/err4.go
new file mode 100644
index 0000000000..8e5f78e987
--- /dev/null
+++ b/misc/cgo/errors/err4.go
@@ -0,0 +1,15 @@
+// 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
+
+/*
+long double x = 0;
+*/
+import "C"
+
+func main() {
+	_ = C.x // ERROR HERE
+	_ = C.x
+}
diff --git a/misc/cgo/errors/test.bash b/misc/cgo/errors/test.bash
index ed0b094692..04747a6913 100755
--- a/misc/cgo/errors/test.bash
+++ b/misc/cgo/errors/test.bash
@@ -37,6 +37,9 @@ expect() {
 check err1.go
 check err2.go
 check err3.go
+if [ $(go env GOARCH) == "amd64" ]; then # If we find a portable test case, we can remove this.
+	check err4.go
+fi
 check issue7757.go
 check issue8442.go
 check issue11097a.go