From a934346614c265e77e42821c67ecd23c33d4a7b8 Mon Sep 17 00:00:00 2001
From: Richard Broker <rbroker@unknown>
Date: Thu, 12 Mar 2015 13:28:18 +0100
Subject: [PATCH] Use SetHandleInformation() to make handle non-inheritable in
 wxMSW.

Simplify the code in wxExecute() by using SetHandleInformation() to make the
handle non-inheritable instead of duplicating it to achieve the same goal (the
old code worked under Windows 9x too, unlike the new one, but we don't care
about them any more).

See #16898.
---
 src/msw/utilsexc.cpp | 37 ++++++++++++-------------------------
 1 file changed, 12 insertions(+), 25 deletions(-)

diff --git a/src/msw/utilsexc.cpp b/src/msw/utilsexc.cpp
index ddcf6282ce..2e297ea642 100644
--- a/src/msw/utilsexc.cpp
+++ b/src/msw/utilsexc.cpp
@@ -694,9 +694,6 @@ long wxExecute(const wxString& cmd, int flags, wxProcess *handler,
 #if wxUSE_STREAMS && !defined(__WXWINCE__)
     wxPipe pipeIn, pipeOut, pipeErr;
 
-    // we'll save here the copy of pipeIn[Write]
-    HANDLE hpipeStdinWrite = INVALID_HANDLE_VALUE;
-
     // open the pipes to which child process IO will be redirected if needed
     if ( handler && handler->IsRedirected() )
     {
@@ -728,27 +725,16 @@ long wxExecute(const wxString& cmd, int flags, wxProcess *handler,
         si.hStdOutput = pipeOut[wxPipe::Write];
         si.hStdError = pipeErr[wxPipe::Write];
 
-        // we must duplicate the handle to the write side of stdin pipe to make
-        // it non inheritable: indeed, we must close the writing end of pipeIn
-        // before launching the child process as otherwise this handle will be
-        // inherited by the child which will never close it and so the pipe
-        // will never be closed and the child will be left stuck in ReadFile()
-        HANDLE pipeInWrite = pipeIn.Detach(wxPipe::Write);
-        if ( !::DuplicateHandle
-                (
-                    ::GetCurrentProcess(),
-                    pipeInWrite,
-                    ::GetCurrentProcess(),
-                    &hpipeStdinWrite,
-                    0,                      // desired access: unused here
-                    FALSE,                  // not inherited
-                    DUPLICATE_SAME_ACCESS   // same access as for src handle
-                ) )
-        {
-            wxLogLastError(wxT("DuplicateHandle"));
-        }
-
-        ::CloseHandle(pipeInWrite);
+        // We must set the handle to the side of the pipes that we won't use in
+        // the child to be non-inheritable. We must do this before launching
+        // the child process as otherwise these handles will be inherited by
+        // the child which will never close them and so the pipe will not
+        // return ERROR_BROKEN_PIPE if the parent or child exits unexpectedly
+        // causing the remaining process to potentially become deadlocked in
+        // ReadFile().
+        if ( !::SetHandleInformation(pipeIn[wxPipe::Write],
+                                     HANDLE_FLAG_INHERIT, 0) )
+            wxLogLastError(wxT("SetHandleInformation(pipeIn)"));
     }
 #endif // wxUSE_STREAMS
 
@@ -889,6 +875,7 @@ long wxExecute(const wxString& cmd, int flags, wxProcess *handler,
         // close the other handles too
         if ( redirect )
         {
+            ::CloseHandle(pipeIn.Detach(wxPipe::Write));
             ::CloseHandle(pipeOut.Detach(wxPipe::Read));
             ::CloseHandle(pipeErr.Detach(wxPipe::Read));
         }
@@ -913,7 +900,7 @@ long wxExecute(const wxString& cmd, int flags, wxProcess *handler,
         wxPipeInputStream *
             errStream = new wxPipeInputStream(pipeErr.Detach(wxPipe::Read));
         wxPipeOutputStream *
-            inStream = new wxPipeOutputStream(hpipeStdinWrite);
+            inStream = new wxPipeOutputStream(pipeIn.Detach(wxPipe::Write));
 
         handler->SetPipeStreams(outStream, inStream, errStream);