lpReserved

lpReserved is a conventional name used in Windows API to denote a reserved pointer field or parameter. The 'lp' prefix reflects historical naming (long pointer) and indicates a pointer value, typically to a string or structure. The field or parameter is reserved by Microsoft for potential future use, and callers are generally expected to treat it as unused.

In practice, applications should initialize any lpReserved member to NULL before calling API functions that take such structures, and should pass NULL for any function parameter named lpReserved unless the documentation specifies otherwise. Using a non-NULL value can lead to undefined behavior.

Commonly, the lpReserved member appears in the STARTUPINFO structure used with CreateProcess. Microsoft Docs specify that this member is reserved for future use and must be NULL when the structure is passed to the API. Similar naming appears in other structures and function prototypes, but behavior depends on the specific API version.

Notes: The exact meaning and requirements for lpReserved can vary by context and Windows version. Always consult the current official documentation for the relevant structure or function to determine whether NULL is required. In modern code, lpReserved is typically unused.