C6333
warning C6333: Invalid parameter: passing MEM_RELEASE and a non-zero dwSize parameter to <function> is not allowed. This results in the failure of this call
This warning indicates an invalid parameter is being passed to VirtualFree or VirtualFreeEx. Both of these functions reject a dwFreeType of MEM_RELEASE with a non-zero value of dwSize. When passing MEM_RELEASE, the dwSize parameter must be zero. Also, make sure that the return value of this function is not ignored.
Example
The following sample code generates this warning:
#include <windows.h>
#define PAGELIMIT 80
DWORD dwPages = 0; // count of pages
DWORD dwPageSize; // page size
VOID f( VOID )
{
LPVOID lpvBase; // base address of the test memory
BOOL bSuccess;
SYSTEM_INFO sSysInfo; // system information
GetSystemInfo( &sSysInfo );
dwPageSize = sSysInfo.dwPageSize;
// Reserve pages in the process's virtual address space
lpvBase = VirtualAlloc(
NULL, // system selects address
PAGELIMIT*dwPageSize,// size of allocation
MEM_RESERVE,
PAGE_NOACCESS );
if (lpvBase)
{
// code to access memory
}
else
{
return;
}
bSuccess = VirtualFree(lpvBase, PAGELIMIT * dwPageSize, MEM_RELEASE);
//code...
}
To correct this warning, use the following sample code:
#include <windows.h>
#define PAGELIMIT 80
DWORD dwPages = 0; // count of pages
DWORD dwPageSize; // page size
VOID f( VOID )
{
LPVOID lpvBase; // base address of the test memory
BOOL bSuccess;
SYSTEM_INFO sSysInfo; // system information
GetSystemInfo( &sSysInfo );
dwPageSize = sSysInfo.dwPageSize;
// Reserve pages in the process's virtual address space
lpvBase = VirtualAlloc(
NULL, // system selects address
PAGELIMIT*dwPageSize,// size of allocation
MEM_RESERVE,
PAGE_NOACCESS );
if (lpvBase)
{
// code to access memory
}
else
{
return;
}
bSuccess = VirtualFree(lpvBase, 0, MEM_RELEASE );
// VirtualFree(lpvBase, PAGELIMIT * dwPageSize, MEM_DECOMMIT);
// code...
}
You can also use VirtualFree(lpvBase, PAGELIMIT * dwPageSize, MEM_DECOMMIT); call to decommit pages, and later release them using MEM_RELEASE flag.