Misha Koshelev wrote:
Hi, thank you very much for your help.
I am implementing Installer::RegistryValue for MSI OLE automation and I need a way to tell apart a VT_EMPTY and a VT_I4 type variant with a value of 0 as these have two different behaviors for this function under Windows XP. I have not figured out a way to do this with DispGetParam (or VariantChangeType for that matter; specifically I made a little test to check every single type and find one that could be coerced to only from a VT_EMPTY but not from a VT_BSTR or a VT_I4 but it did not find any such types; a coercion to a VT_I4 succeeds and makes a variant of value 0 if coercing either a VT_EMPTY variant or a zero value VT_I4 variant). I can always just check directly in the DISPPARAMS structure but that seems to be a little dirty if I am using DispGetParam for everything else.
Installer::RegistryValue will probably be different from the vast majority of other functions in the MSI OLE automation interface because registry values themselves have different types. I would expect it to not use DispGetParam and for the following conversions to take place: VT_I4 -> REG_DWORD VT_BSTR -> REG_SZ VT_EMPTY -> REG_NONE? Everything else or just arrays -> REG_BINARY