PVOID

PVOID is a Windows-specific typedef for a generic pointer to void. It is defined as void in Windows headers and is used to hold references to data of any type without specifying that type in interface definitions. This makes PVOID a common choice in both user-mode and kernel-mode code for passing opaque pointers, buffers, or context information across API boundaries.

Because PVOID is a void pointer, it cannot be dereferenced or used in pointer arithmetic without first casting to a specific type. When using PVOID, programmers typically perform an explicit cast to the expected pointer type before accessing data, for example, MyStruct p = (MyStruct)pvoid; followed by dereferencing p. Memory management and object ownership remain the responsibility of the code using the pointer; PVOID itself does not convey size, type information, or ownership semantics.

In practice, PVOID enables flexible interfaces by allowing a function to accept or return a pointer without enforcing a concrete type on the caller. A common pattern is to pass a PVOID as a context parameter, with the callee casting it to the appropriate type once inside. Other related Windows opaque pointer types include HANDLE (typedef void) and various P-type pointers to internal structures, which serve similar purposes in representing references to system objects or buffers.

Notes on usage: PVOID is widely encountered in driver development, Windows kernel APIs, and certain user-mode APIs that require type-agnostic pointers. While convenient, its use requires careful casting and clear documentation to avoid type-safety issues and risky dereferencing.