_bstr_t to char*, amazing result

Question

first:

LPCTSTR asdfsdf = (LPCTSTR)(_bstr_t)v;
printf("%s\n", asdfsdf);

second:

printf("%s\n", (LPCTSTR)(_bstr_t)v);

they are the same, but the first condition causes unreadable code

why?

Answer 1

The _bstr_t class encapsulates a BSTR inside a C++ class. In your first instance:

LPCTSTR asdfsdf = (LPCTSTR)(_bstr_t)v;

you are creating a _bstr_t object, extracting the LPCTSTR out of it, but then the temporary _bstr_t object gets destructed. Whatever asdfsdf pointed to is now deallocated and can no longer be used.

In your second example

printf("%s\n", (LPCTSTR)(_bstr_t)v);

the temporary _bstr_t object is not destructed until after the printf() is called, so there is no problem using the LPCTSTR value.