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/internal/trace/parser.go b/src/internal/trace/parser.go
index 2e145129eb..a774bf14c9 100644
--- a/src/internal/trace/parser.go
+++ b/src/internal/trace/parser.go
@@ -12,11 +12,25 @@ import (
 	"math/rand"
 	"os"
 	"os/exec"
+	"path/filepath"
+	"runtime"
 	"strconv"
 	"strings"
 	_ "unsafe"
 )
 
+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"
+}
+
 // Event describes one event in the trace.
 type Event struct {
 	Off   int       // offset in input file (for debugging and error reporting)
@@ -757,7 +771,7 @@ func symbolize(events []*Event, bin string) error {
 	}
 
 	// Start addr2line.
-	cmd := exec.Command("go", "tool", "addr2line", bin)
+	cmd := exec.Command(goCmd(), "tool", "addr2line", bin)
 	in, err := cmd.StdinPipe()
 	if err != nil {
 		return fmt.Errorf("failed to pipe addr2line stdin: %v", err)