From 4432cd1c27c82c87fe2507a05a1a940f794b617f Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Thu, 26 Apr 2018 11:20:03 -0400
Subject: [PATCH] cmd/compilebench: fix GOROOT inconsistencies

If GOROOT is unset (as is common now),
then the output of "go env GOROOT" may
differ from the GOROOT inferred by alternate
compilers being executed and also from the
value of runtime.GOROOT() inside compilebench,
used by go/build. Harmonize all of these by
setting GOROOT explicitly (will fix subcommands)
and by invoking the go command to learn about
packages instead of assuming go/build has any
idea what it's doing.

Change-Id: If97aa76cc2afec11a8404975f39329db7eb452e0
Reviewed-on: https://go-review.googlesource.com/109516
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: David Chase <drchase@google.com>
---
 cmd/compilebench/main.go | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/cmd/compilebench/main.go b/cmd/compilebench/main.go
index d2cd70b2..4d3b74ef 100644
--- a/cmd/compilebench/main.go
+++ b/cmd/compilebench/main.go
@@ -67,9 +67,9 @@ package main
 
 import (
 	"bytes"
+	"encoding/json"
 	"flag"
 	"fmt"
-	"go/build"
 	"io/ioutil"
 	"log"
 	"os"
@@ -144,6 +144,7 @@ func main() {
 		log.Fatalf("%s env GOROOT: %v", *flagGoCmd, err)
 	}
 	goroot = strings.TrimSpace(string(s))
+	os.Setenv("GOROOT", goroot) // for any subcommands
 
 	compiler = *flagCompiler
 	if compiler == "" {
@@ -250,11 +251,28 @@ func runBuild(name, dir string, count int) {
 		return
 	}
 
-	pkg, err := build.Import(dir, ".", 0)
+	// Make sure dependencies needed by go tool compile are installed to GOROOT/pkg.
+	out, err := exec.Command(*flagGoCmd, "build", "-i", dir).CombinedOutput()
 	if err != nil {
-		log.Print(err)
+		log.Printf("go build -i %s: %v\n%s", dir, err, out)
 		return
 	}
+
+	// Find dir and source file list.
+	var pkg struct {
+		Dir     string
+		GoFiles []string
+	}
+	out, err = exec.Command(*flagGoCmd, "list", "-json", dir).Output()
+	if err != nil {
+		log.Printf("go list -json %s: %v\n", dir, err)
+		return
+	}
+	if err := json.Unmarshal(out, &pkg); err != nil {
+		log.Printf("go list -json %s: unmarshal: %v", dir, err)
+		return
+	}
+
 	args := []string{"-o", "_compilebench_.o"}
 	if is6g {
 		*flagMemprofilerate = -1