ole help please! invoke fn issue

Marcus Meissner marcus at jet.franken.de
Thu Jun 13 17:02:41 CDT 2002

On Thu, Jun 13, 2002 at 08:39:05PM +0100, Ann and Jason Edmeades wrote:
> Hi all,
> Playing further with my VB program and native oleaut32 I've hit an
> 'interesting issue' with the Microsoft Date/Time picker.
> typelib.c in dlls\oleaut32 assumes all parms are dwords and picks the lval
> of a variant (which for most of the types of variant is the dword containing
> the important information). However as shown by the following trace:
> trace:ole:ITypeInfo_fnInvoke
> (0x404560ac)(0x40418fac,id=20,flags=0x00000004,0x405c5d84,(nil),0x405c5d64,0
> x405c5d94) partial stub!
> trace:ole:dump_DispParms args=1 named args=1
> trace:ole:dump_Variant (0x405c5dec)
> trace:ole:dump_Variant VARTYPE: VT_DATE

> This shows that the function takes one parm and that parm is a variant. We
> pass the value contained in the parm and it fails. We need to ensure the
> whole variant is put on the stack for the called function. Since we
> currently only call with dword parms this wont work.

Actually I think just the DATE part should be out there, which is 8 byte
> This hack takes the parm and puts the variant into that arg and subsequent
> ones, meaning the stack to the called function should look as it would be.
> Unfortunately as it stands this would only work with one parm, so my
> question is how it is supposed to be fixed. I could potentially change
> args[i+1] to args[numArgWords+1] but it still feels very hacky.

No, just reuse _argsize() from tmarshal.c, calculate the number of 
stack positions using this function, allocate enough space, memcpy()
out of the VARIANTS into the stack space and invoke. (I have submitted
a patch to tmarshal.c).

Looking at the code in there ... I think I have to have another,
closer look at it :/

Ciao, Marcus

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