guile: Simplify ioscm_make_gdb_stdio_port

As pointed out by Pedro, it's clearer to do it this way.  We can trust
that scm_mode_bits won't try to modify our string, even though it takes
a non-const char *.

gdb/ChangeLog:

	* guile/scm-ports.c (ioscm_make_gdb_stdio_port): Do not pass a
	local char array to scm_mode_bits, use a cast instead.

2 files changed, 11 insertions, 11 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 5042001..8d08d81 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2015-10-26  Simon Marchi  <simon.marchi@polymtl.ca>
+
+	* guile/scm-ports.c (ioscm_make_gdb_stdio_port): Do not pass a
+	local char array to scm_mode_bits, use a cast instead.
+
 2015-10-26  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* tui/tui-data.c (tui_alloc_content): Don't check xmalloc
diff --git a/gdb/guile/scm-ports.c b/gdb/guile/scm-ports.c
index 5d529b3..ffaa3fd 100644
--- a/gdb/guile/scm-ports.c
+++ b/gdb/guile/scm-ports.c
@@ -357,36 +357,31 @@ ioscm_init_stdio_buffers (SCM port, long mode_bits)
 static SCM
 ioscm_make_gdb_stdio_port (int fd)
 {
+  int is_a_tty = isatty (fd);
   const char *name;
+  const char *mode_str;
   long mode_bits;
   SCM port;
-  char buf[3];
-
-  memset (buf, 0, sizeof (buf));
 
   switch (fd)
     {
     case 0:
       name = input_port_name;
-      buf[0] = 'r';
+      mode_str = is_a_tty ? "r0" : "r";
       break;
     case 1:
       name = output_port_name;
-      buf[0] = 'w';
+      mode_str = is_a_tty ? "w0" : "w";
       break;
     case 2:
       name = error_port_name;
-      buf[0] = 'w';
+      mode_str = is_a_tty ? "w0" : "w";
       break;
     default:
       gdb_assert_not_reached ("bad stdio file descriptor");
     }
 
-  if (isatty (fd))
-    buf[1] = '0';
-
-  mode_bits = scm_mode_bits (buf);
-
+  mode_bits = scm_mode_bits ((char *) mode_str);
   port = ioscm_open_port (stdio_port_desc, mode_bits);
 
   scm_set_port_filename_x (port, gdbscm_scm_from_c_string (name));