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, 2 insertions, 1 deletions

diff --git a/parser.c b/parser.c
index 7662614e..89efaca4 100644
--- a/parser.c
+++ b/parser.c
@@ -498,7 +498,8 @@ void open_txr_file(val spec_file, val *txr_lisp_p, val *name, val *stream)
 #ifdef ENOENT
 except:
 #endif
-      uw_throwf(file_error_s, lit("unable to open ~a"), spec_file_try, nao);
+      uw_throwf(errno_to_file_error(errno),
+                lit("unable to open ~a"), spec_file_try, nao);
     }
 
     *stream = make_stdio_stream(in, spec_file_try);