Question

BSTR DoSOmething()
{
   return L"";
}

OR is it okay to pass TCHAR * to API taking BSTR as input parameter.

Is it okay to convert wchar_t string into BSTR via a return statement.Will it cause some memory corruption?

Answer 1

No, it is not OK because some APIs expect not just a WCHAR* pointer, which BSTR also is, but a real BSTR pointer with length information attached. Still casting this way might often work out well, and this might be misleading.

Everything about BSTRs: Eric’s Complete Guide To BSTR Semantics.

A related quote from there:

2) A BSTR must be allocated and freed with the SysAlloc* family of
functions. A PWSZ can be an automatic-storage buffer from the stack
or allocated with malloc, new, LocalAlloc or any other memory
allocator.

3) A BSTR is of fixed length. A PWSZ may be of any length, limited
only by the amount of valid memory in its buffer.

4) A BSTR always points to the first valid character in the buffer. A
PWSZ may be a pointer to the middle or end of a string buffer.