Windows: Fix --enable-logging to not disable logging when stderr is a pipe

base/process_util_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/process_util.h"
 
 #include <fcntl.h>
 #include <io.h>
 #include <windows.h>
 #include <userenv.h>
@@ skipping 104 matching lines @@
   // it fails quite often. This should be investigated eventually.
   base::KillProcess(process_, kProcessKilledExitCode, false);
 
   // Now, just cleanup as if the process exited normally.
   OnObjectSignaled(process_);
 }
 
 }  // namespace
 
 void RouteStdioToConsole() {
+  // Don't change anything if stdout or stderr already point to a
+  // valid stream.
+  //
+  // If we are running under Buildbot or under Cygwin's default
+  // terminal (mintty), stderr and stderr will be pipe handles.  In
+  // that case, we don't want to open CONOUT$, because its output
+  // likely does not go anywhere.
+  //
+  // We don't use GetStdHandle() to check stdout/stderr here because
+  // it can return dangling IDs of handles that were never inherited
+  // by this process.  These IDs could have been reused by the time
+  // this function is called.  The CRT checks the validity of
+  // stdout/stderr on startup (before the handle IDs can be reused).
+  // _fileno(stdout) will return -2 (_NO_CONSOLE_FILENO) if stdout was
+  // invalid.
+  if (_fileno(stdout) >= 0 || _fileno(stderr) >= 0)
+    return;
+
   if (!AttachConsole(ATTACH_PARENT_PROCESS)) {
     unsigned int result = GetLastError();
     // Was probably already attached.
     if (result == ERROR_ACCESS_DENIED)
       return;
     // Don't bother creating a new console for each child process if the
     // parent process is invalid (eg: crashed).
     if (result == ERROR_GEN_FAILURE)
       return;
     // Make a new console if attaching to parent fails with any other error.
@@ skipping 849 matching lines @@
 
   PERFORMANCE_INFORMATION info;
   if (!InternalGetPerformanceInfo(&info, sizeof(info))) {
     DLOG(ERROR) << "Failed to fetch internal performance info.";
     return 0;
   }
   return (info.CommitTotal * system_info.dwPageSize) / 1024;
 }
 
 }  // namespace base