I'm calling Microsoft's _wspawnv function, and it keeps returning -1 with errno set to 22; errno.h defines this as EINVAL. According to Microsoft's documentation for _wspawnv, this code should only be returned if the mode
parameter is invalid. I've tried calling it with _P_WAIT and _P_NOWAIT in the first parameter, and both return the same error.
Edit: It's amazing how many problems can be solved by going away for a day. It didn't take me long to realize that the filename in the second parameter had quotes around it. Took them out, problem solved.
Moral of the story - don't trust the documentation to tell you everything. I didn't spend a lot of time double-checking the filename because the documentation didn't list it as a possible suspect, even though the error code implied that any parameter might be invalid.