win: crashpad_handler should create its own pipe name in ephemeral mode

handler/crashpad_handler.ad

 // 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,
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 Alternatively, on OS X, this server may be started from launchd(8), where it
 receives the Mach service name in a *--mach-service* argument. It checks in with
 the bootstrap server under this service name, and clients may look it up with
 the bootstrap server under this service name. It monitors this service for
 exception messages. Upon receipt of +SIGTERM+, the server exits after allowing
 any upload in progress to complete. +SIGTERM+ is normally sent by launchd(8)
 when it determines that the server should exit.
 
 On Windows, clients register with this server by communicating with it via the
-named pipe identified by the *--pipe-name* argument. During registration, a
-client provides the server with an OS event object that it will signal should it
-crash. The server obtains the client’s process handle and waits on the crash
-event object for a crash, as well as the client’s process handle for the client
-to exit cleanly without crashing. When the server loses all clients and
-*--persistent* is not specified, it exits after allowing any upload in progress
-to complete.
+named pipe identified by the *--pipe-name* argument. Alternatively, the server
+can create a new pipe with a random name and inform a client of this name via
+the *--handshake-handle* mechanism; clients may then register by communicating
+with it via that named pipe. During registration, a client provides the server
+with an OS event object that it will signal should it crash. The server obtains
+the client’s process handle and waits on the crash event object for a crash, as
+well as the client’s process handle for the client to exit cleanly without
+crashing. When a server started via the *--handshake-handle* mechanism loses all
+of its clients, it exits after allowing any upload in progress to complete.
 
 It is not normally appropriate to invoke this program directly. Usually, it will
 be invoked by a Crashpad client using the Crashpad client library, or started by
 another system service. On OS X, arbitrary programs may be run with a Crashpad
 handler by using man_link:run_with_crashpad[1] to establish the Crashpad client
 environment before running a program.
 
 == Options
 *--annotation*='KEY=VALUE'::
 Sets a process-level annotation mapping 'KEY' to 'VALUE' in each crash report
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 *--mach-service*='SERVICE'::
 Check in with the bootstrap server under the name 'SERVICE'. Either this option
 or *--handshake-fd*, but not both, is required. This option is only valid on OS
 X.
 +
 'SERVICE' may already be reserved with the bootstrap server in cases where this
 tool is started by launchd(8) as a result of a message being sent to a service
 declared in a job’s +MachServices+ dictionary (see launchd.plist(5)). The
 service name may also be completely unknown to the system.
 
-*--persistent*::
-Continue running after the last client exits. If this option is not specified,
-this server will exit as soon as it has no clients, although on startup, it
-always waits for at least one client to connect. This option is only valid on
-Windows.
+*--handshake-handle*='HANDLE'::
+Perform the handshake with the initial client on the HANDLE at 'HANDLE'. Either
+this option or *--pipe-name*, but not both, is required. This option is only
+valid on Windows.
++
+When this option is present, the server creates a new named pipe at a random
+name and informs its client of the name. The server waits for at least one
+client to register, and exits when all clients have exited, after waiting for
+any uploads in progress to complete.
 
 *--pipe-name*='PIPE'::
 Listen on the given pipe name for connections from clients. 'PIPE' must be of
-the form +\\.\pipe\<somename>+. This option is required. This option is only
-valid on Windows.
+the form +\\.\pipe\<somename>+. Either this option or *--handshake-handle*, but
+not both, is required. This option is only valid on Windows.
++
+When this option is present, the server creates a named pipe at 'PIPE', a name
+known to both the server and its clients. The server continues running even
+after all clients have exited.
 
 *--reset-own-crash-exception-port-to-system-default*::
 Causes the exception handler server to set its own crash handler to the system
 default before beginning operation. This is only expected to be useful in cases
 where the server inherits an inappropriate crash handler from its parent
 process. This option is only valid on OS X. Use of this option is discouraged.
 It should not be used absent extraordinary circumstances.
 
 *--url*='URL'::
 If uploads are enabled, sends crash reports to the Breakpad-type crash report
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 Failure, with a message printed to the standard error stream.
 
 == See Also
 
 man_link:catch_exception_tool[1],
 man_link:crashpad_database_util[1],
 man_link:generate_dump[1],
 man_link:run_with_crashpad[1]
 
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