Re: byte alignment/dynamic memory from heap x64

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Tim,

Thanks for the help. I had seen the definition in the WDK header that uses
declspec(align(16)) and I was compiling with x64 compiler.

I had read on msdn that declspec(align(n)) did not work for dynamic
allocation from the heap. At any rate, all is working when I am using
ExAllocatePoolWithTag and casting to my pointer.

thanks,
Mike



"Tim Roberts" wrote:

Mike L <MikeL@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

My IM driver uses SLIST_ENTRY and SLIST_HEADER(s) and they are declared in a
struct and when my driver is loaded I dynamically allocate memory using these
structs.

for example(not my real struct...)

struct X {

int y;
PNDIS_BUFFER pBuf;
....
SLIST_HEADER ListHeader;
SLIST_ENTRY ListEntry;
...
};

The documention for x64 states that SLIST_ENTRY and SLIST_HEADER must be 16
byte aligned.

How do I force this to happen ?

You don't have to. A few minutes browsing through the include files will
show that SLIST_HEADER and SLIST_ENTRY are already declared with 16-byte
alignment. As long as your structure starts on a 16-byte boundary, the
header and entry structures will be so aligned.

Any advice is appreciated, I might have a bug in my code for one of the
above methods, so I really just need someone to tell me how this is normally
done and I can figure out the details. I saw another function
_align_memory, but did not want to link an NDIS driver to the c runtime for
memory management, but maybe that is another alternative.

You're sure you are compiling for x64? In the 32-bit build environments,
they aren't 16-byte aligned because they don't need to be.
--
Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.

.

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