lib: more nuanced file access errors.

Several new more specific exception types are derived from
file-error and used. Error handlers can distinguish unexpected
non-existence, unexpected existence and permission errors
from each other and other errors.

* lib.c (path_not_found_s, path_exists_s, path_permission_s):
New symbol variables.
(obj_init): New variables initialized.

* lib.h (path_not_found_s, path_exists_s, path_permission_s):
Declared.

* parser.c (open_txr_file): Use new errno_to_file_error
function to convert errno to exception symbol.

* socket.c (open_sockfd): Likewise.

* stream.c (open_directory, open_file, open_fileno,
open_command, open_process, run, remove_path, rename_path):
Likewise, and process-error is used in open_process and run
instead of file-error for problems related to creating the
process.

* sysif.c (errno_to_file_error): New function.
(mkdir_wrap, ensure_dir, chdir_wrap, getcwd_wrap, mknod_wrap,
chmod_wrap, symlink_wrap, link_wrap, readlink_wrap, stat_impl,
umask_wrap, ): Use
errno_to_file_error to convert errno to exception symbol.
(exec_wrap): Use process-error instead of file-error.

* sysif.c (errno_to_file_error): Declared.

* unwind.c (uw_init): Register path-not-found, path-exists and
path-permission as subtypes of file-error.

* txr.1: Documented.

1 files changed, 5 insertions, 1 deletions

diff --git a/txr.1 b/txr.1
index 640c1e16..e2529d9b 100644
--- a/txr.1
+++ b/txr.1
@@ -38478,7 +38478,11 @@ subtype of every exception type:
                       |
                       +--- query-error
                       |
-                      +--- file-error
+                      +--- file-error -------+--- path-not-found
+                      |                      |
+                      |                      +--- path-exists
+                      |                      |
+                      |                      +--- path-permission
                       |
                       +--- process-error
                       |