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NdisAllocateMemoryWithTag function

Note   NDIS 5. x has been deprecated and is superseded by NDIS 6. x. For new NDIS driver development, see Network Drivers Starting with Windows Vista. For information about porting NDIS 5. x drivers to NDIS 6. x, see Porting NDIS 5.x Drivers to NDIS 6.0.

NdisAllocateMemoryWithTag allocates resident (nonpaged) system-space memory.


NDIS_STATUS NdisAllocateMemoryWithTag(
  _Out_ PVOID *VirtualAddress,
  _In_  UINT  Length,
  _In_  ULONG Tag


VirtualAddress [out]

Pointer to a caller-supplied variable in which this function returns the base virtual address of the allocated memory or NULL if sufficient nonpaged memory is currently unavailable.

Length [in]

Specifies the size in bytes to be allocated.

Tag [in]

Is a string, delimited by single quote marks, with up to four characters, usually specified in reversed order. The NDIS-supplied default tag for this call is 'maDN', but the caller can override this default by supplying an explicit value.

Return value

NdisAllocateMemoryWithTag can return either of the following:

Return codeDescription

The caller can use the allocated memory range starting at the value returned at VirtualAddress.


An attempt to allocate the requested memory failed. This return does not necessarily mean that a subsequent call will fail.



A call to NdisAllocateMemoryWithTag is equivalent to calling NdisAllocateMemory, except that NdisAllocateMemoryWithTag allows the caller to supply a tag that appears in any crash dump of the system that occurs subsequently.

During driver development on a checked build of the system, this function also can be useful for crash debugging. Calling this routine, rather than NdisAllocateMemory, inserts the caller-supplied tag into a crash dump of pool memory.

The Tag passed to this function is more readable if its characters are reversed when NdisAllocateMemoryWithTag is called. For example, if a caller passes 'Fred' as a Tag, it would appear as 'derF' if pool is dumped or when tracking pool usage in the debugger. The NDIS-supplied default tag appears as 'NDam' (indicating NDISallocatememory) when pool is dumped.


Target platform



Not supported for NDIS 6.0 drivers in Windows Vista. NdisAllocateMemoryWithTagPriority. Supported for NDIS 5.1 drivers in Windows Vista and Windows XP.


Ndis.h (include Ndis.h)



See also




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