* cygheap.h (cygheap_fdmanip::cygheap_fdmanip): Clear fh.

(cygheap_fdmanip::isopen): New method.
* syscalls.cc (_read): Avoid accessing closed fd.
* path.h (fe_types): New enum.
(path_conv::set_path): New method.
(find_exec): Change null_if_not_found argument to something more generic.
* spawn.cc (find_exec): Default to returning the POSIX path rather than the
windows path, unless instructed otherwise.
(spawn_guts): Force call to find_exec to use native paths.
* dlfcn.cc (check_path_access): Accommodate new find_exec arguments.
* environ.h (win_env::get_posix): New method.

winsup/cygwin/syscalls.cc

@@ -322,6 +322,9 @@ _read (int fd, void *ptr, size_t len)
 	  goto out;
 	}
 
+      if (!cfd.isopen())
+	return -1;
+
       /* Check to see if this is a background read from a "tty",
 	 sending a SIGTTIN, if appropriate */
       res = cfd->bg_check (SIGTTIN);