createthread

CreateThread is a Windows API function that creates a new thread of execution within the calling process. It returns a handle to the new thread, which can be used with synchronization and wait functions, and to query or control the thread’s state. The new thread begins execution at the function pointed to by lpStartAddress and is passed the lpParameter as its single argument. The thread runs concurrently with the creating thread until it terminates or the process ends.

The function signature involves six parameters. lpThreadAttributes can specify a security descriptor for the thread object or be NULL for defaults. dwStackSize requests an initial stack size in bytes, with 0 indicating the default size. lpStartAddress is a pointer to the thread procedure, a function that matches the DWORD WINAPI ThreadProc(LPVOID) signature. lpParameter is passed to the thread procedure as its sole parameter. dwCreationFlags can be 0 or include CREATE_SUSPENDED to start the thread in a suspended state. pdwThreadId receives the thread identifier, if non-NULL.

If CREATE_SUSPENDED is specified, the thread starts in a suspended state and must be resumed with ResumeThread to begin execution. On failure, CreateThread returns NULL and extended error information is available via GetLastError. The thread’s exit code is the DWORD returned by the thread procedure or supplied by ExitThread, and it can be retrieved with GetExitCodeThread after termination. The caller should close the thread handle with CloseHandle to free resources.

Practical use involves careful synchronization and data sharing between threads. Developers should consider whether to use CreateThread directly or alternatives such as _beginthreadex, which initializes the C runtime for the new thread, or CreateRemoteThread for injecting threads into other processes. Proper lifecycle management and error handling are essential to robust multithreaded applications.