os/exec: allow open descriptors to be closed during TestPipeLookPathLeak

In https://build.golang.org/log/d2eb315305bf3d513c490e7f85d56e9a016aacd2,
we observe a failure in TestPipeLookPathLeak due to an additional
descriptor (7) that was open at the start of the test being closed while
the test executes.

I haven't dug much into the failure, but it seems plausible to me that the
descriptor may have been opened by libc for some reason, and may have been
closed due to some sort of idle timeout or the completion of a background
initialization routine.

Since the test is looking for a leak, and closing an existing descriptor
does not indicate a leak, let's not fail the test if an existing descriptor
is unexpectedly closed.

Updates #5071.

Change-Id: I03973ddff6592c454cfcc790d6e56accd051dd52
Reviewed-on: https://go-review.googlesource.com/c/go/+/447235
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/os/exec/exec_test.go b/src/os/exec/exec_test.go
index 3c1fffd951cb12003fe93a27350afb58a1d8162c..7f1f99330dde77267fbcfd1403cef7450a73a627 100644 (file)
--- a/src/os/exec/exec_test.go
+++ b/src/os/exec/exec_test.go
@@ -26,7 +26,6 @@ import (
        "os/exec/internal/fdtest"
        "os/signal"
        "path/filepath"
-       "reflect"
        "runtime"
        "runtime/debug"
        "strconv"
@@ -641,7 +640,11 @@ func TestPipeLookPathLeak(t *testing.T) {
                return fds
        }
 
-       want := openFDs()
+       old := map[uintptr]bool{}
+       for _, fd := range openFDs() {
+               old[fd] = true
+       }
+
        for i := 0; i < 6; i++ {
                cmd := exec.Command("something-that-does-not-exist-executable")
                cmd.StdoutPipe()
@@ -651,9 +654,16 @@ func TestPipeLookPathLeak(t *testing.T) {
                        t.Fatal("unexpected success")
                }
        }
-       got := openFDs()
-       if !reflect.DeepEqual(got, want) {
-               t.Errorf("set of open file descriptors changed: got %v, want %v", got, want)
+
+       // Since this test is not running in parallel, we don't expect any new file
+       // descriptors to be opened while it runs. However, if there are additional
+       // FDs present at the start of the test (for example, opened by libc), those
+       // may be closed due to a timeout of some sort. Allow those to go away, but
+       // check that no new FDs are added.
+       for _, fd := range openFDs() {
+               if !old[fd] {
+                       t.Errorf("leaked file descriptor %v", fd)
+               }
        }
 }