Merge the specpdl and backtrace stacks. Make the structure of the

specpdl entries more obvious via a tagged union of structs.
* src/lisp.h (BITS_PER_PTRDIFF_T): New constant.
(enum specbind_tag): New enum.
(struct specbinding): Make it a tagged union of structs.
Add a case for backtrace records.
(specpdl_symbol, specpdl_old_value, specpdl_where, specpdl_arg)
(specpdl_func, backtrace_function, backtrace_nargs, backtrace_args)
(backtrace_debug_on_exit): New accessors.
(struct backtrace): Remove.
(struct catchtag): Remove backlist field.
* src/data.c (let_shadows_buffer_binding_p, let_shadows_global_binding_p):
Move to eval.c.
(Flocal_variable_p): Speed up the common case where the binding is
already loaded.
* src/eval.c (backtrace_list): Remove.
(set_specpdl_symbol, set_specpdl_old_value): Remove.
(set_backtrace_args, set_backtrace_nargs)
(set_backtrace_debug_on_exit, backtrace_p, backtrace_top)
(backtrace_next): New functions.
(Fdefvaralias, Fdefvar): Adjust to new specpdl format.
(unwind_to_catch, internal_lisp_condition_case)
(internal_condition_case, internal_condition_case_1)
(internal_condition_case_2, internal_condition_case_n): Don't bother
with backtrace_list any more.
(Fsignal): Adjust to new backtrace format.
(grow_specpdl): Move up.
(record_in_backtrace): New function.
(eval_sub, Ffuncall): Use it.
(apply_lambda): Adjust to new backtrace format.
(let_shadows_buffer_binding_p, let_shadows_global_binding_p): Move from
data.c.
(specbind): Adjust to new specpdl format.  Simplify.
(record_unwind_protect, unbind_to): Adjust to new specpdl format.
(Fbacktrace_debug, Fbacktrace, Fbacktrace_frame): Adjust to new
backtrace format.
(mark_backtrace): Remove.
(mark_specpdl, get_backtrace, backtrace_top_function): New functions.
* src/xdisp.c (redisplay_internal): Use record_in_backtrace.
* src/alloc.c (Fgarbage_collect): Use record_in_backtrace.
Use mark_specpdl.
* src/profiler.c (record_backtrace): Use get_backtrace.
(handle_profiler_signal): Use backtrace_top_function.
* src/.gdbinit (xbacktrace, hookpost-backtrace): Use new backtrace
accessor functions.

1 files changed, 2 insertions, 15 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 7a56c78e2ba..cce0fff4fd4 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -5165,7 +5165,6 @@ returns nil, because real GC can't be done.
 See Info node `(elisp)Garbage Collection'.  */)
   (void)
 {
-  struct specbinding *bind;
   struct buffer *nextb;
   char stack_top_variable;
   ptrdiff_t i;
@@ -5174,7 +5173,6 @@ See Info node `(elisp)Garbage Collection'.  */)
   EMACS_TIME start;
   Lisp_Object retval = Qnil;
   size_t tot_before = 0;
-  struct backtrace backtrace;
 
   if (abort_on_gc)
     emacs_abort ();
@@ -5185,12 +5183,7 @@ See Info node `(elisp)Garbage Collection'.  */)
     return Qnil;
 
   /* Record this function, so it appears on the profiler's backtraces.  */
-  backtrace.next = backtrace_list;
-  backtrace.function = Qautomatic_gc;
-  backtrace.args = &Qnil;
-  backtrace.nargs = 0;
-  backtrace.debug_on_exit = 0;
-  backtrace_list = &backtrace;
+  record_in_backtrace (Qautomatic_gc, &Qnil, 0);
 
   check_cons_list ();
 
@@ -5257,11 +5250,7 @@ See Info node `(elisp)Garbage Collection'.  */)
   for (i = 0; i < staticidx; i++)
     mark_object (*staticvec[i]);
 
-  for (bind = specpdl; bind != specpdl_ptr; bind++)
-    {
-      mark_object (bind->symbol);
-      mark_object (bind->old_value);
-    }
+  mark_specpdl ();
   mark_terminals ();
   mark_kboards ();
 
@@ -5295,7 +5284,6 @@ See Info node `(elisp)Garbage Collection'.  */)
       mark_object (handler->var);
     }
   }
-  mark_backtrace ();
 #endif
 
 #ifdef HAVE_WINDOW_SYSTEM
@@ -5486,7 +5474,6 @@ See Info node `(elisp)Garbage Collection'.  */)
       malloc_probe (swept);
     }
 
-  backtrace_list = backtrace.next;
   return retval;
 }