+/* Unbuffer STREAM. This is a wrapper around setbuf(STREAM, nullptr)
+ which applies some special rules for MS-Windows hosts. */
+
+static void
+unbuffer_stream (FILE *stream)
+{
+ /* Unbuffer the input stream so that in gdb_readline_no_editing_callback,
+ the calls to fgetc fetch only one char at the time from STREAM.
+
+ This is important because gdb_readline_no_editing_callback will read
+ from STREAM up to the first '\n' character, after this GDB returns to
+ the event loop and relies on a select on STREAM indicating that more
+ input is pending.
+
+ If STREAM is buffered then the fgetc calls may have moved all the
+ pending input from the kernel into a local buffer, after which the
+ select will not indicate that more input is pending, and input after
+ the first '\n' will not be processed immediately.
+
+ Please ensure that any changes in this area run the MI tests with the
+ FORCE_SEPARATE_MI_TTY=1 flag being passed. */
+
+#ifdef __MINGW32__
+ /* With MS-Windows runtime, making stdin unbuffered when it's
+ connected to the terminal causes it to misbehave. */
+ if (!ISATTY (stream))
+ setbuf (stream, nullptr);
+#else
+ /* On GNU/Linux the issues described above can impact GDB even when
+ dealing with input from a terminal. For now we unbuffer the input
+ stream for everyone except MS-Windows. */
+ setbuf (stream, nullptr);
+#endif
+}
+