Question

I tried passing an std::string via RPC, but I got the following error:

MIDL2025: syntax error: expecting a
type specification or a storage
specifer or a type qualifier near
“string”

Extract from code:

interface TestInterface
{
    unsigned int HelloUser([in] const string user);
}

Is this possible?

Answer 1

You must use a BSTR. Also, no const. By specifying the argument as [in], it is already understood that the callee will not modify the string, and even if it did modify, it won’t be marshaled back to the caller.

The _bstr_t class will help with conversion. Note that BSTR is always based on WCHAR, which is 16-bit. Thus, use std::wstring.