Misc minor simplifications in C code.

* src/buffer.c (Fset_buffer_multibyte): Signal an error instead of widening.
(Fmake_overlay): Remove redundant tests.
* src/coding.h (ENCODE_FILE, DECODE_FILE, DECODE_SYSTEM): Remove special
case for the special 0 coding-system.
* src/frame.c (Fmake_terminal_frame): Prefer safer CONSP over !NILP.

5 files changed, 19 insertions, 14 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 555f5cdf3f0..50b8e793717 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -619,6 +619,8 @@ inefficiency, and not namespace-clean.
 
 * Incompatible Lisp Changes in Emacs 24.3
 
+** set-buffer-multibyte now signals an error in narrowed buffers.
+
 +++
 ** (random) by default now returns a different random sequence in
 every Emacs run.  Use (random S), where S is a string, to set the
diff --git a/src/ChangeLog b/src/ChangeLog
index 56e75b5efce..507fe80c8ab 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,13 @@
+2012-10-02  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+        * frame.c (Fmake_terminal_frame): Prefer safer CONSP over !NILP.
+
+        * coding.h (ENCODE_FILE, DECODE_FILE, DECODE_SYSTEM): Remove special
+        case for the special 0 coding-system.
+
+        * buffer.c (Fset_buffer_multibyte): Signal an error instead of widening.
+        (Fmake_overlay): Remove redundant tests.
+
 2012-10-02  Juanma Barranquero  <lekktu@gmail.com>
 
         * makefile.w32-in ($(BLD)/alloc.$(O), $(BLD)/gmalloc.$(O)):
diff --git a/src/buffer.c b/src/buffer.c
index 580ea671b43..6925675fd5a 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2464,7 +2464,7 @@ current buffer is cleared.  */)
     begv = BEGV, zv = ZV;
 
   if (narrowed)
-    Fwiden ();
+    error ("Changing multibyteness in a narrowed buffer");
 
   if (NILP (flag))
     {
@@ -3847,17 +3847,16 @@ for the rear of the overlay advance when text is inserted there
   end = OVERLAY_END (overlay);
   if (OVERLAY_POSITION (end) < b->overlay_center)
     {
-      if (b->overlays_after)
-        XOVERLAY (overlay)->next = b->overlays_after;
+      eassert (b->overlays_after);
+      XOVERLAY (overlay)->next = b->overlays_after;
       set_buffer_overlays_after (b, XOVERLAY (overlay));
     }
   else
     {
-      if (b->overlays_before)
-        XOVERLAY (overlay)->next = b->overlays_before;
+      eassert (b->overlays_before);
+      XOVERLAY (overlay)->next = b->overlays_before;
       set_buffer_overlays_before (b, XOVERLAY (overlay));
     }
-
   /* This puts it in the right list, and in the right order.  */
   recenter_overlay_lists (b, b->overlay_center);
 
@@ -4141,7 +4140,7 @@ DEFUN ("overlays-at", Foverlays_at, Soverlays_at, 1, 1, 0,
   /* Put all the overlays we want in a vector in overlay_vec.
      Store the length in len.  */
   noverlays = overlays_at (XINT (pos), 1, &overlay_vec, &len,
-                           0, 0, 0);
+                           NULL, NULL, 0);
 
   /* Make a list of them all.  */
   result = Flist (noverlays, overlay_vec);
diff --git a/src/coding.h b/src/coding.h
index c45d2ef86e2..989552bf667 100644
--- a/src/coding.h
+++ b/src/coding.h
@@ -646,10 +646,8 @@ struct coding_system
    for file names, if any.  */
 #define ENCODE_FILE(name)                                                  \
   (! NILP (Vfile_name_coding_system)                                       \
-   && !EQ (Vfile_name_coding_system, make_number (0))                      \
    ? code_convert_string_norecord (name, Vfile_name_coding_system, 1)      \
    : (! NILP (Vdefault_file_name_coding_system)                            \
-      && !EQ (Vdefault_file_name_coding_system, make_number (0))           \
       ? code_convert_string_norecord (name, Vdefault_file_name_coding_system, 1) \
       : name))
 
@@ -658,10 +656,8 @@ struct coding_system
    for file names, if any.  */
 #define DECODE_FILE(name)                                                  \
   (! NILP (Vfile_name_coding_system)                                       \
-   && !EQ (Vfile_name_coding_system, make_number (0))                      \
    ? code_convert_string_norecord (name, Vfile_name_coding_system, 0)      \
    : (! NILP (Vdefault_file_name_coding_system)                            \
-      && !EQ (Vdefault_file_name_coding_system, make_number (0))           \
       ? code_convert_string_norecord (name, Vdefault_file_name_coding_system, 0) \
       : name))
 
@@ -670,7 +666,6 @@ struct coding_system
    for system functions, if any.  */
 #define ENCODE_SYSTEM(str)                                                 \
   (! NILP (Vlocale_coding_system)                                          \
-   && !EQ (Vlocale_coding_system, make_number (0))                         \
    ? code_convert_string_norecord (str, Vlocale_coding_system, 1)          \
    : str)
 
@@ -678,7 +673,6 @@ struct coding_system
    for system functions, if any.  */
 #define DECODE_SYSTEM(str)                                                 \
   (! NILP (Vlocale_coding_system)                                          \
-   && !EQ (Vlocale_coding_system, make_number (0))                         \
    ? code_convert_string_norecord (str, Vlocale_coding_system, 0)          \
    : str)
 
diff --git a/src/frame.c b/src/frame.c
index edb90038a48..2fcf7275f9c 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -632,7 +632,7 @@ affects all frames on the same terminal device.  */)
     Lisp_Object terminal;
 
     terminal = Fassq (Qterminal, parms);
-    if (!NILP (terminal))
+    if (CONSP (terminal))
       {
         terminal = XCDR (terminal);
         t = get_terminal (terminal, 1);