Platform SDK: Memory |
The VirtualFree function releases, decommits, or releases and decommits a region of pages within the virtual address space of the calling process.
To free memory allocated in another process by the VirtualAllocEx function, use the VirtualFreeEx function.
BOOL VirtualFree( LPVOID lpAddress, // address of region SIZE_T dwSize, // size of region DWORD dwFreeType // operation type );
Value | Meaning |
---|---|
MEM_DECOMMIT | Decommits the specified region of committed pages.
An attempt to decommit an uncommitted page will not cause the function to fail. This means that a range of committed or uncommitted pages can be decommitted without having to worry about a failure. |
MEM_RELEASE | Releases the specified region of reserved pages. If this value is specified, the dwSize parameter must be zero, or the function fails. |
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To get extended error information, call GetLastError.
VirtualFree can perform one of the following operations:
Pages that have been released are free pages available for subsequent allocation operations. Attempting to read from or write to a free page results in an access violation exception.
VirtualFree can decommit an uncommitted page; this means that a range of committed or uncommitted pages can be decommitted without having to worry about a failure. Decommitting a page releases its physical storage, either in memory or in the paging file on disk. If a page is decommitted but not released, its state changes to reserved, and it can be committed again by a subsequent call to VirtualAlloc. Attempting to read from or write to a reserved page results in an access violation exception.
The current state of the entire range of pages must be compatible with the type of free operation specified by the dwFreeType parameter. Otherwise, the function fails and no pages are released or decommitted.
Windows NT/2000: Requires Windows NT 3.1 or later.
Windows 95/98: Requires Windows 95 or later.
Header: Declared in Winbase.h; include Windows.h.
Library: Use Kernel32.lib.
Memory Management Overview, Memory Management Functions, VirtualFreeEx