COM from MASM32

[axtens]

Okay, I'll keep it short this time.

I have a COM DLL that I wrote in Delphi. It exposes a function which accepts a WideString and returns a Boolean.

I'm using the COM plugin for RadASM.
The GUIDs are:

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sIID_IConverters textequ <{08DD3E3E3h,05DF7h,04BA8h,{08Ch,000h,02Dh,022h,0DEh,0FFh,081h,090h}}>
IID_IConverters GUID sIID_IConverters
sCLSID_Converters textequ <{00CF7C6A0h,0981Dh,04C2Ch,{0A7h,04Ch,026h,0DDh,071h,03Ch,022h,0BEh}}>
CLSID_Converters GUID sCLSID_Converters

The following works:

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invoke CoInitializeEx,0,0
MOV hResult, rv(CoCreateInstance,ADDR CLSID_Converters,NULL,CLSCTX_SERVER,ADDR IID_IConverters,ADDR pIConverters)

but I'm quite at a loss to figure out how to pass in the address of the returned boolean. I've tried putting it in .data? and as a LOCAL, as a WORD / DWORD / VARIANT / VARIANT_BOOL but to no effect. The RadASM plugin says that I should have code like this:

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mov eax,pIConverters
mov edx,[eax]
push /VT_BOOL/
;Parameters ( sName )
push /VT_VARIANT/
push pIConverters
;call IConverters._IsEnc
call dword ptr [edx+30*4]


I'm fairly sure I'm doing the right thing with the push of the VT_VARIANT for the sName parameter: that's done as

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mov pWideAllocStr,rv(SysAllocString,sEncoding)
where pWideAllocStr is defined as a LOCAL DWORD and the sEncoding is arriving as a pointer to a widestring. pWideAllocStr ends up pointing to a BSTR.

The chunk in question is

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mov eax,pIConverters
mov edx,[eax]
push offset bIsEncoding ;defined in .data? as bIsEncoding DW ?
;Parameters ( sName )
push pWideAllocStr
push pIConverters
;call IConverters._IsEnc
call dword ptr [edx+30*4]


Running with a VB6 testing program, the program dies immediately after the call

Can anyone tell me what I'm doing wrong? Is there a better way?

Kind regards,
Bruce.

[axtens]

Hmm... seems  I hadn't done it right. Funny what stopping for lunch does, that and praying about it.

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mov pWideAllocStr,rv(SysAllocString,sEncoding)
MOV var.vt, VT_BSTR
MOV EAX, pWideAllocStr
MOV var.bstrVal, EAX

mov eax,pIConverters
mov edx,[eax]
push bIsEncoding
;Parameters ( sName )
push var
push pIConverters
;call IConverters._IsEnc
call dword ptr [edx+30*4]
that gets past the call. So far so good.

Kind regards,
Bruce.

[axtens]

Grrrrrr

Okay, it's not crashing, but it's still not working. The string parameter is not being passed to the DLL. The DLL is being called, but nothing's getting passed.

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IsEncoding PROC STDCALL uses EDI ESI EBX sEncoding:DWORD

;LOCAL bIsEncoding:WORD
;LOCAL pSTR:DWORD
;LOCAL lpWideCharStr[128]:BYTE
LOCAL pWideAllocStr:DWORD
LOCAL nLen:DWORD
LOCAL arg1:VARIANT
LOCAL res1:VARIANT

PUSH EDX
PUSH ECX

mov pWideAllocStr,rv(SysAllocString,sEncoding)

MOV arg1.vt, VT_BSTR
MOV EDX, pWideAllocStr
MOV arg1.bstrVal, EDX

DumpMem ADDR arg1, sizeof VARIANT

MOV res1.vt, VT_BOOL

mov eax,pIConverters
mov edx,[eax]
;push bIsEncoding
push res1
;Parameters ( sName )
push arg1
push pIConverters
;call IConverters._IsEnc
call dword ptr [edx+30*4]

PrintHex EAX
PrintLine
fn SysFreeString,pWideAllocStr
MOVZX EAX, bIsEncoding
POP ECX
POP EDX
ret

IsEncoding endp