test: introduce common.runWithInvalidFD()

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

PR-URL: #18864
Fixes: #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>

test/common/README.md

@@ -139,6 +139,14 @@ consisting of all `ArrayBufferView` and an `ArrayBuffer`.
 
 Returns the file name and line number for the provided Function.
 
+### runWithInvalidFD(func)
+* `func` [<Function>]
+
+Runs `func` with an invalid file descriptor that is an unsigned integer and
+can be used to trigger `EBADF` as the first argument. If no such file
+descriptor could be generated, a skip message will be printed and the `func`
+will not be run.
+
 ### globalCheck
 * [<boolean>]
 

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');