streams: tightening sloppy argument defaulting.

Numerous functions in TXR Lisp treat a nil argument for an
optional parameter as if it were omitted.  In the case of
streams, this can cause problems.  An accidental nil passed to
an input function can cause it to read from standard input and
hang. In this patch, argument defaulting is tighented for
functions that perform I/O. It's mostly stream parameters, but
not exclusively.

* eval.c (prinl, pprinl): Use default_arg_strict to default
the stream argument, and also re-use that value for the
put_char call.

* lib.c (lazy_stream_cons, print, pprint, put_json): Use
default_arg_strict rather than default_arg.

* parser.c (regex_parse, lisp_parse_impl, txr_parse): Tighten
the defaulting of the input stream and error stream arguments,
streamlining the logic at the same time.

* stream.c (do_parse_mode): Use default_arg_strict for the
mode string argument.
(record_adapter, get_line, get_char, get_byte, get_bytes,
unget_byte, put_buf, fill_buf, fill_buf_adjust,
get_line_as_buf, put_string, put_char, put_byte, put_line,
flush_stream, get_string): Use strict defaulting for stream
argument.
(mkstemp_wrap): Use strict defaulting for suffix.

1 files changed, 4 insertions, 4 deletions

diff --git a/lib.c b/lib.c
index 56a548ec..3d168bf4 100644
--- a/lib.c
+++ b/lib.c
@@ -8888,7 +8888,7 @@ static val lazy_stream_func(val env, val lcons)
 
 val lazy_stream_cons(val stream)
 {
-  stream = default_arg(stream, std_input);
+  stream = default_arg_strict(stream, std_input);
 
   if (real_time_stream_p(stream)) {
     return make_lazy_cons(func_f1(stream, simple_lazy_stream_func));
@@ -13739,13 +13739,13 @@ val obj_print(val obj, val out, val pretty)
 
 val print(val obj, val stream, val pretty)
 {
-  return obj_print(obj, default_arg(stream, std_output),
+  return obj_print(obj, default_arg_strict(stream, std_output),
                    default_null_arg(pretty));
 }
 
 val pprint(val obj, val stream)
 {
-  return obj_print(obj, default_arg(stream, std_output), t);
+  return obj_print(obj, default_arg_strict(stream, std_output), t);
 }
 
 val tostring(val obj)
@@ -13764,7 +13764,7 @@ val tostringp(val obj)
 
 val put_json(val obj, val stream_in, val flat)
 {
-  val stream = default_arg(stream_in, std_output);
+  val stream = default_arg_strict(stream_in, std_output);
   val imode = if3(default_null_arg(flat),
                   set_indent_mode(stream, num_fast(indent_foff)),
                   test_set_indent_mode(stream, num_fast(indent_off),