all: correct location of go tool

In general, there are no guarantee that `go` command exist on $PATH.
This CL tries to get `go` command from $GOROOT/bin instead.

There are three kinds of code we should handle:
    For normal code, the CL implements goCmd() or goCmdName().
    For unit tests, the CL uses testenv.GoTool() or testenv.GoToolPath().
    For integration tests, the CL sets PATH=$GOROOT/bin:$PATH in cmd/dist.

Note that make.bash sets PATH=$GOROOT/bin:$PATH in the build process.
So this change is only useful when we use toolchain manually.

Updates #21875

Change-Id: I963b9f22ea732dd735363ececde4cf94a5db5ca2
Reviewed-on: https://go-review.googlesource.com/64650
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 15 insertions, 1 deletions

diff --git a/src/cmd/trace/pprof.go b/src/cmd/trace/pprof.go
index 40803ac5f9..47be2a6d1c 100644
--- a/src/cmd/trace/pprof.go
+++ b/src/cmd/trace/pprof.go
@@ -15,10 +15,24 @@ import (
 	"net/http"
 	"os"
 	"os/exec"
+	"path/filepath"
+	"runtime"
 
 	"github.com/google/pprof/profile"
 )
 
+func goCmd() string {
+	var exeSuffix string
+	if runtime.GOOS == "windows" {
+		exeSuffix = ".exe"
+	}
+	path := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
+	if _, err := os.Stat(path); err == nil {
+		return path
+	}
+	return "go"
+}
+
 func init() {
 	http.HandleFunc("/io", serveSVGProfile(pprofIO))
 	http.HandleFunc("/block", serveSVGProfile(pprofBlock))
@@ -147,7 +161,7 @@ func serveSVGProfile(prof func(w io.Writer) error) http.HandlerFunc {
 			return
 		}
 		svgFilename := blockf.Name() + ".svg"
-		if output, err := exec.Command("go", "tool", "pprof", "-svg", "-output", svgFilename, blockf.Name()).CombinedOutput(); err != nil {
+		if output, err := exec.Command(goCmd(), "tool", "pprof", "-svg", "-output", svgFilename, blockf.Name()).CombinedOutput(); err != nil {
 			http.Error(w, fmt.Sprintf("failed to execute go tool pprof: %v\n%s", err, output), http.StatusInternalServerError)
 			return
 		}