[Emacs-diffs] Changes to emacs/etc/DEBUG

[Eli Zaretskii]

Index: emacs/etc/DEBUG
diff -c emacs/etc/DEBUG:1.20 emacs/etc/DEBUG:1.21
*** emacs/etc/DEBUG:1.20        Fri Oct 26 16:21:57 2001
--- emacs/etc/DEBUG     Thu Dec  6 07:35:13 2001
***************
*** 258,263 ****
--- 258,306 ----
  the backtrace when Emacs stops inside that function will show what
  code causes the X protocol errors.
  
+ Some bugs related to the X protocol disappear when Emacs runs in a
+ synchronous mode.  To track down those bugs, we suggest the following
+ procedure:
+ 
+   - Run Emacs under a debugger and put a breakpoint inside the
+     primitive function which, when called from Lisp, triggers the X
+     protocol errors.  For example, if the errors happen when you
+     delete a frame, put a breakpoint inside `Fdelete_frame'.
+ 
+   - When the breakpoint breaks, step through the code, looking for
+     calls to X functions (the ones whose names begin with "X" or
+     "Xt" or "Xm").
+ 
+   - Insert calls to `XSync' before and after each call to the X
+     functions, like this:
+ 
+        XSync (f->output_data.x->display_info->display, 0);
+ 
+     where `f' is the pointer to the `struct frame' of the selected
+     frame, normally available via XFRAME (selected_frame).  (Most
+     functions which call X already have some variable that holds the
+     pointer to the frame, perhaps called `f' or `sf', so you shouldn't
+     need to compute it.)
+ 
+     If your debugger can call functions in the program being debugged,
+     you should be able to issue the calls to `XSync' without recompiling
+     Emacs.  For example, with GDB, just type:
+ 
+        call XSync (f->output_data.x->display_info->display, 0)
+ 
+     before and immediately after the suspect X calls.  If your
+     debugger does not support this, you will need to add these pairs
+     of calls in the source and rebuild Emacs.
+ 
+     Either way, systematically step through the code and issue these
+     calls until you find the first X function called by Emacs after
+     which a call to `XSync' winds up in the function
+     `x_error_quitter'.  The first X function call for which this
+     happens is the one that generated the X protocol error.
+ 
+   - You should now look around this offending X call and try to figure
+     out what is wrong with it.
+ 
  ** If the symptom of the bug is that Emacs fails to respond
  
  Don't assume Emacs is `hung'--it may instead be in an infinite loop.