From c7e91724c0e1f514982e90d7d08bb2c291a2bc43 Mon Sep 17 00:00:00 2001
From: Andrew Gerrand <adg@golang.org>
Date: Mon, 9 Jan 2012 14:24:05 +1100
Subject: [PATCH] go/build: handle and warn of duplicate GOPATH entries

R=golang-dev, alex.brainman
CC=golang-dev
https://golang.org/cl/5519050
---
 src/pkg/go/build/path.go | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/pkg/go/build/path.go b/src/pkg/go/build/path.go
index 7a281800c2..bb9b8ca642 100644
--- a/src/pkg/go/build/path.go
+++ b/src/pkg/go/build/path.go
@@ -157,6 +157,7 @@ func init() {
 		Path = []*Tree{t}
 	}
 
+Loop:
 	for _, p := range filepath.SplitList(os.Getenv("GOPATH")) {
 		if p == "" {
 			continue
@@ -166,6 +167,21 @@ func init() {
 			log.Printf("invalid GOPATH %q: %v", p, err)
 			continue
 		}
+
+		// Check for dupes.
+		// TODO(alexbrainman): make this correct under windows (case insensitive).
+		for _, t2 := range Path {
+			if t2.Path != t.Path {
+				continue
+			}
+			if t2.Goroot {
+				log.Printf("GOPATH is the same as GOROOT: %q", t.Path)
+			} else {
+				log.Printf("duplicate GOPATH entry: %q", t.Path)
+			}
+			continue Loop
+		}
+
 		Path = append(Path, t)
 		gcImportArgs = append(gcImportArgs, "-I", t.PkgDir())
 		ldImportArgs = append(ldImportArgs, "-L", t.PkgDir())
-- 
2.50.0