MachMessageServer: don’t deal with MACH_SEND_TRAILER

util/mach/mach_message_server.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 91 matching lines @@
   }
 
   mach_msg_size_t trailer_alloc = REQUESTED_TRAILER_SIZE(options);
   mach_msg_size_t max_request_size = interface->MachMessageServerRequestSize();
   mach_msg_size_t request_alloc = round_page(max_request_size + trailer_alloc);
   mach_msg_size_t request_size = (options & MACH_RCV_LARGE)
                                      ? request_alloc
                                      : max_request_size + trailer_alloc;
 
   mach_msg_size_t max_reply_size = interface->MachMessageServerReplySize();
-  mach_msg_size_t reply_alloc = round_page(
-      (options & MACH_SEND_TRAILER) ? (max_reply_size + MAX_TRAILER_SIZE)
-                                    : max_reply_size);
+
+  // mach_msg_server() and mach_msg_server_once() would consider whether
+  // |options| contains MACH_SEND_TRAILER and include MAX_TRAILER_SIZE in this
+  // computation if it does, but that option is ineffective on OS X.
+  mach_msg_size_t reply_alloc = round_page(max_reply_size);
 
   kern_return_t kr;
 
   do {
     mach_msg_size_t this_request_alloc = request_alloc;
     mach_msg_size_t this_request_size = request_size;
 
     base::mac::ScopedMachVM request_scoper;
     mach_msg_header_t* request_header = nullptr;
 
@@ skipping 132 matching lines @@
         // persistent mode, and just return success when not in persistent mode.
         return (persistent == kPersistent) ? MACH_RCV_TIMED_OUT : kr;
       }
     }
   } while (persistent == kPersistent);
 
   return kr;
 }
 
 }  // namespace crashpad