Issue #1686 - Kill iexplore.exe and AdblockplusEngine.exe processes from the installer

installer/src/installer-lib/process.cpp

 #include <stdexcept>
 #include <functional>
 #include <wctype.h>
 // <thread> is C++11, but implemented in VS2012
 #include <thread>
 
 #include "installer-lib.h"
 #include "process.h"
 #include "handle.h"
 #include "session.h"
@@ skipping 198 matching lines @@
 * The present use of this method is not closing dozens of applications, so delay performance is not critical.
 *
 * \return
 *   The negation of is_running.
 *   If is_running() was true at the beginning, then this function will have run refresh() before returning.
 *
 * \sa
 *   - MSDN [WM_QUERYENDSESSION message](http://msdn.microsoft.com/en-us/library/windows/desktop/aa376890%28v=vs.85%29.aspx)
 *   - MSDN [WM_ENDSESSION message](http://msdn.microsoft.com/en-us/library/windows/desktop/aa376889%28v=vs.85%29.aspx)
 */
-bool ProcessCloser::ShutDown()
+bool ProcessCloser::ShutDown(ImmediateSession& session)
 {
   /*
   * If we're not running, we don't need to shut down.
   */
   if ( ! IsRunning() )
   {
     return true ;
   }
 
   /*
@@ skipping 43 matching lines @@
         /*
         * Send WM_CLOSE to every admissible window.
         */
         send_message m( WM_CLOSE, 0, 0 ) ;
         iterate_our_windows( m ) ;
       }
       break ;
 
     case 4:
       /*
-      * We're out of ways to try to shut down. Oh well. Take cover. It gets violent here.
+      * Oh well. Take cover. It gets violent here. Try to kill all matching processes.
       */
       for (auto it = pid_set.begin(); it != pid_set.end(); ++it)
       {
         HANDLE tmpHandle = OpenProcess(PROCESS_TERMINATE, FALSE, *it);
-        if (!tmpHandle) continue;
+        if (!tmpHandle) 
+        {
+          std::ostringstream stream;
+          stream << "Can't open process for termination. Error: " << GetLastError();

[Eric, 2015/05/14 15:09:25]

This message should indicate a warning rather than an error. This avoids
confusing reporting with respect to a race condition.

The issue is that we are working from a process snapshot in the past, not the
perfectly-current process set. During the interval between then and now, the IE
process may have closed itself down as previously instructed. As a result, a
failure of 'OpenProcess' does not in itself reflect whether we have a process
that terminated itself and is now gone (not an error, just the effect of the
race condition), and a hard error from a process that's still present that we
can't open.

It would be possible to add more checks to distinguish these two, but I'm not
sure it's worth it.

A suggestion:
"Did not open a process scheduled for termination; it may or may not still
exist. OpenProcess() error code = "

+          session.Log(stream.str());
+          continue;
+        }
         Windows_Handle procHandle(tmpHandle);
-        TerminateProcess(tmpHandle, 0);
+        if (!TerminateProcess(tmpHandle, 0))
+        {
+          std::ostringstream stream;
+          stream << "Can't terminate process. Error: " << GetLastError();
+          session.Log(stream.str());
+        }
       }
       break;
 
     default:
+      // We're out of ways to try to shut down. 
       return false;
     }
 
     /*
     * Wait loop.
     */
     for ( unsigned int j = 0 ; j < 50 ; ++ j )
     {
       std::this_thread::sleep_for( std::chrono::milliseconds( 30 ) ) ;
       Refresh() ;
       if ( ! IsRunning() )
       {
         return true ;
       }
     }
     // Assert is_running()
   }
   // No control path leaves the for-loop.
 } ;