Fix Process.runSync on 64-bit Mac OS

runtime/bin/process_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include "bin/process.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 620 matching lines @@
   }
 
   int alive = 3;
   while (alive > 0) {
     // Blocking call waiting for events from the child process.
     if (TEMP_FAILURE_RETRY(poll(fds, alive, -1)) <= 0) {
       return CloseProcessBuffers(fds);
     }
 
     // Process incoming data.
-    for (int i = 0; i < alive; i++) {
+    int current_alive = alive;
+    for (int i = 0; i < current_alive; i++) {
       if (fds[i].revents & POLLIN) {
         intptr_t avail = FDUtils::AvailableBytes(fds[i].fd);
         if (fds[i].fd == out) {
           if (!out_data.Read(out, avail)) {
             return CloseProcessBuffers(fds);
           }
         } else if (fds[i].fd == err) {
           if (!err_data.Read(err, avail)) {
             return CloseProcessBuffers(fds);
           }
         } else if (fds[i].fd == exit_event) {
           if (avail == 8) {
             intptr_t b = TEMP_FAILURE_RETRY(read(exit_event,
                                                  exit_code_data.bytes, 8));
             if (b != 8) {
               return CloseProcessBuffers(fds);
             }
           }
         } else {
           UNREACHABLE();
         }
       }
-    }
-
-    // Process closed.
-    for (int i = 0; i < alive; i++) {
       if (fds[i].revents & POLLHUP) {
         VOID_TEMP_FAILURE_RETRY(close(fds[i].fd));
         alive--;
         if (i < alive) {
           fds[i] = fds[alive];
         }
       }
     }
   }
 
@@ skipping 22 matching lines @@
 
 
 intptr_t Process::CurrentProcessId() {
   return static_cast<intptr_t>(getpid());
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)