Tightening behavior for unimplemented stream ops.

In many cases, if a stream operation is not applicable to a stream, it
is not appropriate to just do nothing and return nil. An error
must be thrown.

* stream.c (unimpl, unimpl_put_string, unimpl_put_char,
unimpl_put_byte, unimpl_get_line, unimpl_get_char, unimpl_get_byte,
unimpl_unget_char, unimpl_unget_byte, unimpl_seek, null_put_string,
null_put_char, null_put_byte, null_get_line, null_get_char,
null_get_byte, null_close, null_flush, null_seek, null_set_prop,
null_get_error, null_get_error_str, null_clear_error): New
static functions.
(fill_stream_ops): New function.
(null_ops): Use null_put_string, etc., instead of null pointers.
(stdio_clear_error, dir_clear_error, cat_clear_error): Return value now
indicating whether an error was cleared.
(stream_set_prop, stream_get_prop, real_time_stream_p, close_stream,
get_error, get_error_str, clear_error, get_line, get_char, get_byte,
unget_char, unget_byte, put_string, put_char, put_byte,
flush_stream): Do not test whether a function in the ops table
is defined; just call it, and return its value.
(stream_init): Call fill_stream_ops on all stream operation
structures so any null pointers are defaulted to appropriate
functions.

* stream.h (struct strm_ops): clear_error gets return value.
(fill_stream_ops): Declared.

* syslog.c (syslog_init): Call fill_stream_ops on syslog_strm_ops.

1 files changed, 2 insertions, 1 deletions

diff --git a/stream.h b/stream.h
index ed947577..2162045e 100644
--- a/stream.h
+++ b/stream.h
@@ -47,7 +47,7 @@ struct strm_ops {
   val (*set_prop)(val, val ind, val);
   val (*get_error)(val);
   val (*get_error_str)(val);
-  void (*clear_error)(val);
+  val (*clear_error)(val);
 };
 
 #define strm_ops_init(cobj_init_macro, put_string, put_char, put_byte,      \
@@ -77,6 +77,7 @@ extern val format_s;
 
 extern val stdin_s, stdout_s, stddebug_s, stderr_s, stdnull_s;
 
+void fill_stream_ops(struct strm_ops *ops);
 val make_null_stream(void);
 val make_stdio_stream(FILE *, val descr);
 val make_tail_stream(FILE *, val descr);