In SessionHandler::gc, we use a virtual call to PS(default_mod)->s_gc to
call the gc implementation. That return value is checked against
FAILURE (-1).
One of the call targets of PS(default_mod)->s_gc is ps_gc_files().
ps_gc_files() calls to ps_files_cleanup_dir(). The latter function has
some error checks and outputs a notice if something goes wrong. In cases
of errors, the function returns 0. This means that the check in
SessionHandler::gc will misinterpret this as a success and report that 0
files have been *successfully* cleaned up. Fix it by returning -1 to
indicate something *did* go wrong.
Closes GH-10644.
nielsdos
da3ce6015d