The issue I alluded to is a subtle misfeature in the Windows
implementation of execvp (and similar Posix functions): the arguments
you pass via the argv array get concatenated into a single
command-line string, and that string is passed to the Windows system
API that actually invokes the program.  So argv[] elements that
include whitespace need to be quoted(!) to work correctly on
MS-Windows.  (Of course, this quoting must be ifdef'ed away for Posix
platforms.)