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, 4 insertions, 0 deletions

diff --git a/lib.c b/lib.c
index 342e4837..2446bf17 100644
--- a/lib.c
+++ b/lib.c
@@ -108,6 +108,7 @@ val error_s, type_error_s, internal_error_s, panic_s;
 val numeric_error_s, range_error_s;
 val query_error_s, file_error_s, process_error_s, syntax_error_s;
 val timeout_error_s, system_error_s, alloc_error_s;
+val path_not_found_s, path_exists_s, path_permission_s;
 val warning_s, defr_warning_s, restart_s, continue_s;
 val gensym_counter_s, nullify_s, from_list_s, lambda_set_s, length_s;
 val rplaca_s, rplacd_s, seq_iter_s;
@@ -10844,6 +10845,9 @@ static void obj_init(void)
   system_error_s = intern(lit("system-error"), user_package);
   timeout_error_s = intern(lit("timeout-error"), user_package);
   alloc_error_s = intern(lit("alloc-error"), user_package);
+  path_not_found_s = intern(lit("path-not-found"), user_package);
+  path_exists_s = intern(lit("path-exists"), user_package);
+  path_permission_s = intern(lit("path-permission"), user_package);
   assert_s = intern(lit("assert"), user_package);
   warning_s = intern(lit("warning"), user_package);
   defr_warning_s = intern(lit("defr-warning"), user_package);