Can someone explain the c++ FAILED function?

Question

I've seen a lot of example c++ code that wraps function calls in a FAILED() function/method/macro. Could someone explain to me how this works? And if possible does anyone know a c# equivalent?

Answer 1

It generally checks COM function errors. But checking any function that returns a HRESULT is what it's meant for, specifically. FAILED returns a true value if the HRESULT value is negative, which means that the function failed ("error" or "warning" severity). Both S_OK and S_FALSE are >= 0 and so they are not used to convey an error. With "negative" I mean that the high bit is set for HRESULT error codes, i.e., their hexadecimal representation, which can be found in, e.g., winerror.h, begins with an 8, as in 0x8000FFFF.