Bugfix: crash in get_line.

Incorrect, irrelevant handle test inside stdio_get_line
virtual function fails to detect closed stream, leading
to a null pointer passed to the stdio library.

* stream.c (snarf_line): Rewrite according to pattern
followed by the other functions. We must test h->f for
null, not stream->co.handle, which never goes null
until the object is being reclaimed by gc.

1 files changed, 6 insertions, 8 deletions

diff --git a/stream.c b/stream.c
index fd170bc0..a1a41036 100644
--- a/stream.c
+++ b/stream.c
@@ -584,16 +584,14 @@ static wchar_t *snarf_line(struct stdio_handle *h)
 
 static val stdio_get_line(val stream)
 {
-  errno = 0;
-  if (stream->co.handle == 0) {
-    return stdio_maybe_read_error(stream);
-  } else {
-    struct stdio_handle *h = coerce(struct stdio_handle *, stream->co.handle);
+  struct stdio_handle *h = coerce(struct stdio_handle *, stream->co.handle);
+  if (h->f) {
     wchar_t *line = snarf_line(h);
-    if (!line)
-      return stdio_maybe_read_error(stream);
-    return string_own(line);
+    if (line)
+      return string_own(line);
   }
+
+  return stdio_maybe_read_error(stream);
 }
 
 static val stdio_get_char(val stream)