From 3d5ac37d36ecae90a634515b78608062fc9729be Mon Sep 17 00:00:00 2001
From: Zach Shaftel
Date: Sun, 14 Jun 2020 17:20:48 -0400
Subject: Revert "Store bytecode offset within exec_byte_code"

This reverts commit f6ec28d7974785b625e395d57cb18d1f2110fe4c.

This commit was just a terrible idea. Caused segfaults, violated the
comment in lisp.h that only eval.c should access `union specbinding`,
and didn't even improve performance.
---
 src/bytecode.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

(limited to 'src/bytecode.c')

diff --git a/src/bytecode.c b/src/bytecode.c
index f4900fc588f..29b76f88ef7 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -311,6 +311,8 @@ enum byte_code_op
 
 #define TOP (*top)
 
+#define UPDATE_OFFSET (backtrace_byte_offset = pc - bytestr_data);
+
 DEFUN ("byte-code", Fbyte_code, Sbyte_code, 3, 3, 0,
        doc: /* Function used internally in byte-compiled code.
 The first argument, BYTESTR, is a string of byte code;
@@ -378,8 +380,6 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, Lisp_Object maxdepth,
   memcpy (bytestr_data, SDATA (bytestr), bytestr_length);
   unsigned char const *pc = bytestr_data;
   ptrdiff_t count = SPECPDL_INDEX ();
-  union specbinding *bt_frame = specpdl_ptr;
-  bt_frame = backtrace_next (bt_frame);
 
   if (!NILP (args_template))
     {
@@ -426,16 +426,14 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, Lisp_Object maxdepth,
 	 Threading provides a performance boost.  These macros are how
 	 we allow the code to be compiled both ways.  */
 #ifdef BYTE_CODE_THREADED
-#define UPDATE_OFFSET(to)					\
-      if (bt_frame->kind == SPECPDL_BACKTRACE)			\
-	bt_frame->bt.bytecode_offset = (to);
+
       /* The CASE macro introduces an instruction's body.  It is
 	 either a label or a case label.  */
 #define CASE(OP) insn_ ## OP
       /* NEXT is invoked at the end of an instruction to go to the
 	 next instruction.  It is either a computed goto, or a
 	 plain break.  */
-#define NEXT goto *(targets[op = FETCH])
+#define NEXT UPDATE_OFFSET goto *(targets[op = FETCH])
       /* FIRST is like NEXT, but is only used at the start of the
 	 interpreter body.  In the switch-based interpreter it is the
 	 switch, so the threaded definition must include a semicolon.  */
@@ -637,7 +635,6 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, Lisp_Object maxdepth,
 		  }
 	      }
 #endif
-	    UPDATE_OFFSET(pc - bytestr_data);
 	    TOP = Ffuncall (op + 1, &TOP);
 	    NEXT;
 	  }
@@ -1454,7 +1451,7 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, Lisp_Object maxdepth,
 	unbind_to (count, Qnil);
       error ("binding stack not balanced (serious byte compiler bug)");
     }
-  UPDATE_OFFSET(-1);
+  backtrace_byte_offset = -1;
   Lisp_Object result = TOP;
   SAFE_FREE ();
   return result;
-- 
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