test: introduce common.runWithInvalidFD()

This provides a more reliable way to get a fd that can be used
to tirgger EBADF.

PR-URL: https://github.com/nodejs/node/pull/18864
Fixes: https://github.com/nodejs/node/issues/18820
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 13 insertions, 0 deletions

diff --git a/test/common/index.js b/test/common/index.js
index 54b146814a..10fd637af9 100644
--- a/test/common/index.js
+++ b/test/common/index.js
@@ -816,6 +816,19 @@ function restoreWritable(name) {
   delete process[name].writeTimes;
 }
 
+exports.runWithInvalidFD = function(func) {
+  let fd = 1 << 30;
+  // Get first known bad file descriptor. 1 << 30 is usually unlikely to
+  // be an valid one.
+  try {
+    while (fs.fstatSync(fd--) && fd > 0);
+  } catch (e) {
+    return func(fd);
+  }
+
+  exports.printSkipMessage('Could not generate an invalid fd');
+};
+
 exports.hijackStdout = hijackStdWritable.bind(null, 'stdout');
 exports.hijackStderr = hijackStdWritable.bind(null, 'stderr');
 exports.restoreStdout = restoreWritable.bind(null, 'stdout');