The %p format specifier is handled immediately. It requires
that tm_hour is already set. This falls flat in case the am/pm
marker preceeds the time specification. Locales with am/pm
marker preceeding time spec by default exist (e. g. ko_KR).
Also, the code expects that tm_hour might be set to an invalid
value because the %p specifier is used in conjunction with %H.
But this usage is invalid in itself and now catched as error
condition after commit 343a2a5581 ("Cygwin: strptime: make
sure to fail on invalid input digits").
Change the %H/%I/%p handling according to GLibC, i. e.
- fix tm_hour for pm only if the time value has been specified
as 12 hour time %I, and
- perform the fixup only after the entire input has been scanned.
This decouples the fixup from the %p position relativ to %I.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>