Prefer comments /* like this */ in C code

Emacs C code assumes C99 features, but has long used traditional
comments /* like this */ instead of C99-style comments // like this.
Stick with traditional comments for now, partly for style, partly as
it may be safer with compilers that are not fully in C99 mode.

src/emacs-module.c

@@ -142,8 +142,8 @@ static emacs_value const module_nil = 0;
    or a pointer to handle non-local exits.  The function must have an
    ENV parameter.  The function will return the specified value if a
    signal or throw is caught.  */
-// TODO: Have Fsignal check for CATCHER_ALL so we only have to install
-// one handler.
+/* TODO: Have Fsignal check for CATCHER_ALL so we only have to install
+   one handler.  */
 #define MODULE_HANDLE_NONLOCAL_EXIT(retval)                     \
   MODULE_SETJMP (CONDITION_CASE, module_handle_signal, retval); \
   MODULE_SETJMP (CATCHER_ALL, module_handle_throw, retval)
@@ -163,7 +163,7 @@ static emacs_value const module_nil = 0;
    code after the macro may longjmp back into the macro, which means
    its local variable C must stay live in later code.  */
 
-// TODO: Make backtraces work if this macros is used.
+/* TODO: Make backtraces work if this macros is used.  */
 
 #define MODULE_SETJMP_1(handlertype, handlerfunc, retval, c, dummy)	\
   if (module_non_local_exit_check (env) != emacs_funcall_exit_return)	\

src/gfilenotify.c

@@ -105,7 +105,7 @@ dir_monitor_callback (GFileMonitor *monitor,
 
 	  /* Store it into the input event queue.  */
 	  kbd_buffer_store_event (&event);
-	  // XD_DEBUG_MESSAGE ("%s", XD_OBJECT_TO_STRING (event.arg));
+	  /* XD_DEBUG_MESSAGE ("%s", XD_OBJECT_TO_STRING (event.arg));  */
 	}
 
       /* Cancel monitor if file or directory is deleted.  */

src/gtkutil.c

@@ -185,7 +185,7 @@ xg_display_open (char *display_name, Display **dpy)
 {
   GdkDisplay *gdpy;
 
-  unrequest_sigio ();  // See comment in x_display_ok, xterm.c.
+  unrequest_sigio ();  /* See comment in x_display_ok, xterm.c.  */
   gdpy = gdk_display_open (display_name);
   request_sigio ();
   if (!gdpy_def && gdpy)

src/image.c

@@ -3712,7 +3712,7 @@ xpm_load (struct frame *f, struct image *img)
     }
 
 #ifdef USE_CAIRO
-  // Load very specific Xpm:s.
+  /* Load very specific Xpm:s.  */
   if (rc == XpmSuccess
       && img->ximg->format == ZPixmap
       && img->ximg->bits_per_pixel == 32
@@ -3736,7 +3736,7 @@ xpm_load (struct frame *f, struct image *img)
               int maskidx = mid ? i * img->mask_img->bytes_per_line + k/8 : 0;
               int mask = mid ? mid[maskidx] & (1 << (k % 8)) : 1;
 
-              if (mask) od[idx] = id[idx] + 0xff000000; // ff => full alpha
+              if (mask) od[idx] = id[idx] + 0xff000000; /* ff => full alpha */
               else od[idx] = bgcolor;
             }
         }

src/kqueue.c

@@ -264,8 +264,6 @@ kqueue_compare_dir_list (Lisp_Object watch_object)
     report_file_error ("New list not empty", new_dl);
   if (! NILP (pending_dl))
     report_file_error ("Pending events list not empty", pending_dl);
-  //  if (! NILP (deleted_dl))
-  //    report_file_error ("Deleted events list not empty", deleted_dl);
 
   /* Replace old directory listing with the new one.  */
   XSETCDR (Fnthcdr (make_number (3), watch_object),

src/w32fns.c

@@ -6934,7 +6934,7 @@ value of DIR as in previous invocations; this is standard Windows behavior.  */)
   } new_file_details_w;
 
 #ifdef NTGUI_UNICODE
-  wchar_t filename_buf_w[32*1024 + 1]; // NT kernel maximum
+  wchar_t filename_buf_w[32*1024 + 1]; /* NT kernel maximum */
   OPENFILENAMEW * file_details_w = &new_file_details_w.details;
   const int use_unicode = 1;
 #else /* not NTGUI_UNICODE */

src/xdisp.c

@@ -24461,7 +24461,7 @@ calc_pixel_width_or_height (double *res, struct it *it, Lisp_Object prop,
 	    }
 	  if (FRAME_WINDOW_P (it->f) && valid_xwidget_spec_p (prop))
 	    {
-              // TODO: Don't return dummy size.
+              /* TODO: Don't return dummy size.  */
               return OK_PIXELS (100);
             }
 #endif

src/xselect.c

@@ -693,7 +693,7 @@ x_reply_selection_request (struct selection_input_event *event,
 			     : format_bytes);
 	    XFlush (display);
 	    had_errors_p = x_had_errors_p (display);
-            // See comment above about property_change_reply.
+            /* See comment above about property_change_reply.  */
             set_property_change_object (cs->wait_object);
 	    unblock_input ();
 
@@ -1393,7 +1393,7 @@ receive_incremental_selection (struct x_display_info *dpyinfo,
   wait_object = expect_property_change (display, window, property,
 					PropertyNewValue);
   XFlush (display);
-  // See comment in x_reply_selection_request about property_change_reply.
+  /* See comment in x_reply_selection_request about property_change_reply.  */
   set_property_change_object (wait_object);
   unblock_input ();
 
@@ -1433,7 +1433,8 @@ receive_incremental_selection (struct x_display_info *dpyinfo,
       XDeleteProperty (display, window, property);
       wait_object = expect_property_change (display, window, property,
 					    PropertyNewValue);
-      // See comment in x_reply_selection_request about property_change_reply.
+      /* See comment in x_reply_selection_request about
+	 property_change_reply.  */
       set_property_change_object (wait_object);
       XFlush (display);
       unblock_input ();

src/xsmfns.c

@@ -170,7 +170,7 @@ smc_save_yourself_CB (SmcConn smcConn,
   char *smid_opt, *chdir_opt = NULL;
   Lisp_Object user_login_name = Fuser_login_name (Qnil);
 
-  // Must have these.
+  /* Must have these.  */
   if (! STRINGP (Vinvocation_name) || ! STRINGP (user_login_name))
     return;
 

src/xterm.c

@@ -11950,7 +11950,7 @@ x_term_init (Lisp_Object display_name, char *xrm_option, char *resource_name)
 
 #else /* not USE_X_TOOLKIT */
   XSetLocaleModifiers ("");
-  unrequest_sigio ();  // See comment in x_display_ok.
+  unrequest_sigio ();  /* See comment in x_display_ok.  */
   dpy = XOpenDisplay (SSDATA (display_name));
   request_sigio ();
 #endif /* not USE_X_TOOLKIT */