test::Multiprocess: exit cleanly from children with _exit()

util/test/multiprocess.h

 // 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 146 matching lines @@
  private:
   //! \brief Runs the parent side of the test.
   //!
   //! This method establishes the parent’s environment and calls
   //! MultiprocessParent().
   void RunParent();
 
   //! \brief Runs the child side of the test.
   //!
   //! This method establishes the child’s environment, calls
-  //! MultiprocessChild(), and exits cleanly. However, if any failure (via fatal
-  //! or nonfatal gtest assertion) is detected, the child will exit with a
-  //! failure status.
+  //! MultiprocessChild(), and exits cleanly by calling `_exit(0)`. However, if
+  //! any failure (via fatal or nonfatal gtest assertion) is detected, the child
+  //! will exit with a failure status.
   void RunChild();
 
   //! \brief The subclass-provided parent routine.
   //!
   //! Test failures should be reported via gtest: `EXPECT_*()`, `ASSERT_*()`,
   //! `FAIL()`, etc.
   //!
   //! This method must not use a `wait()`-family system call to wait for the
   //! child process to exit, as this is handled by this class.
   //!
   //! Subclasses must implement this method to define how the parent operates.
   virtual void MultiprocessParent() = 0;
 
   //! \brief The subclass-provided child routine.
   //!
   //! Test failures should be reported via gtest: `EXPECT_*()`, `ASSERT_*()`,
   //! `FAIL()`, etc.
   //!
   //! Subclasses must implement this method to define how the child operates.
+  //! Subclasses may exit with a failure status by using `LOG(FATAL)`,
+  //! `abort()`, or similar. They may exit cleanly by returning from this method
+  //! or by calling `_exit(0)`. Under no circumstances may `exit()` be called
+  //! by the child without having the child process `exec()`. Use
+  //! MultiprocessExec if the child should call `exec()`.
   virtual void MultiprocessChild() = 0;
 
   internal::MultiprocessInfo* info_;
   int code_;
   TerminationReason reason_;
 
   DISALLOW_COPY_AND_ASSIGN(Multiprocess);
 };
 
 }  // namespace test
 }  // namespace crashpad
 
 #endif  // CRASHPAD_UTIL_TEST_MULTIPROCESS_H_