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Discrepancy in !objsize in hex and decimal

I use !objsize command to get the true value of an object. For example when I run the command below, it tells me that size of object at address 00000003a275f218 is 18 hex which translates to 24 in decimal.

0:000> !ObjSize 00000003a275f218 
sizeof(00000003a275f218) = 24 (0x18) bytes

So far so good. I am running same command on an object and its size seem to have a discrepancy between hex and decimal. enter image description here

So the size in hex is 0xafbde200. When I convert it to decimal using my calc, this comes to be 2948456960 whereas the output of command is showing decimal size to be -1346510336. Can someone help me understand why there is difference in sizes?

Solution

  • It's a bug in SOS. If you look at the source code, you'll find the method declared as

    DECLARE_API(ObjSize)

    It uses the following format as output

    ExtOut("sizeof(%p) = %d (0x%x) bytes (%S)\n", SOS_PTR(obj), size, size, methodTable.GetName());

    As you can see it uses %d as the format specifier, which is for signed decimal integers. That should be %u for unsigned decimal integers instead, since obviously you can't have objects using negative amount of memory.

    If you know how to use Git, you may provide a patch.

    You can use ? in WinDbg to see the unsigned value:

    0:000> ? 0xafbde200
Evaluate expression: 2948456960 = 00000000`afbde200