Windows Threading: _beginthread, _beginthreadex, or CreateThread – Which API Should I Use?

Windows Threading: Understanding the Differences Between _beginthread, _beginthreadex, and CreateThread in C

When working with multithreading in Windows applications, developers often face the question of which API to use for thread creation: _beginthread, _beginthreadex, or CreateThread. While each function has its advantages and disadvantages, understanding their key differences is crucial for making an informed decision.

CreateThread: A Raw Win32 API

CreateThread is a fundamental Win32 API call that directly creates a new thread in the kernel. It offers low-level control over thread creation parameters, including stack size, priority, and security attributes. However, CreateThread does not perform any additional setup or cleanup tasks required for C library functionality.

_beginthread and _beginthreadex: C Runtime Library Wrappers

_beginthread and _beginthreadex are C runtime library functions that wrap CreateThread. These functions call CreateThread under the hood but handle additional tasks necessary for the C runtime library to operate properly within the new thread. They set up core data structures, such as thread local storage and synchronize thread-safe CRT functions (_tprintf, _strtime, etc.).

Key Considerations When Choosing

When choosing among these functions, consider the following factors:

• C Runtime Library Compatibility:
  If your C application links to the C runtime library (MSVCRT*.dll/.lib), _beginthreadex should be used. It ensures proper initialization and use of CRT resources in the new thread.
• Additional Control:
  CreateThread provides more flexibility for customization and fine-grain control over thread creation. However, it requires explicit handling of CRT initialization and thread cleanup.
• Thread Priorities:
  Both _beginthread and _beginthreadex respect the thread priority value passed to CreateThread.
• Error Handling:
  CreateThread returns detailed error information when thread creation fails. _beginthread and _beginthreadex do not provide additional error handling capabilities.

_endthread and WaitForSingleObject:

_endthread, if called in the newly created thread, is not recognized by CreateThread but is understood by _beginthread/_beginthreadex. Thus, when using _beginthread, WaitForSingleObject on the returned handle will work properly. Note that _endthread does not terminate the thread but rather signals its intention to exit.

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