Revert "pythongh-101865: Remove deprecated co_lnotab from code obje…

…cts as per PEP626"

This reverts commit 06a79d9.

Doc/library/inspect.rst

@@ -164,6 +164,10 @@ attributes (see :ref:`import-mod-attrs` for module attributes):
 |           |                   | read more :ref:`here      |
 |           |                   | <inspect-module-co-flags>`|
 +-----------+-------------------+---------------------------+
+|           | co_lnotab         | encoded mapping of line   |
+|           |                   | numbers to bytecode       |
+|           |                   | indices                   |
++-----------+-------------------+---------------------------+
 |           | co_freevars       | tuple of names of free    |
 |           |                   | variables (referenced via |
 |           |                   | a function's closure)     |

Doc/reference/datamodel.rst

@@ -962,6 +962,7 @@ Internal types
          single: co_filename (code object attribute)
          single: co_firstlineno (code object attribute)
          single: co_flags (code object attribute)
+         single: co_lnotab (code object attribute)
          single: co_name (code object attribute)
          single: co_names (code object attribute)
          single: co_nlocals (code object attribute)
@@ -988,7 +989,9 @@ Internal types
       a tuple containing the literals used by the bytecode; :attr:`co_names` is
       a tuple containing the names used by the bytecode; :attr:`co_filename` is
       the filename from which the code was compiled; :attr:`co_firstlineno` is
-      the first line number of the function; :attr:`co_stacksize` is the
+      the first line number of the function; :attr:`co_lnotab` is a string
+      encoding the mapping from bytecode offsets to line numbers (for details
+      see the source code of the interpreter); :attr:`co_stacksize` is the
       required stack size; :attr:`co_flags` is an integer encoding a number
       of flags for the interpreter.
 

Doc/whatsnew/3.12.rst

@@ -700,10 +700,6 @@ Removed
   *context* parameter instead.
   (Contributed by Victor Stinner in :gh:`94172`.)
 
-* Remove ``co_lnotab`` attribute from code objects per :pep:`626`:
-  use ``co_lines`` method instead.
-  (Contributed by Nikita Sobolev in :gh:`101865`.)
-
 
 Porting to Python 3.12
 ======================

Lib/inspect.py

@@ -499,6 +499,7 @@ def iscode(object):
         co_freevars         tuple of names of free variables
         co_posonlyargcount  number of positional only arguments
         co_kwonlyargcount   number of keyword only arguments (not including ** arg)
+        co_lnotab           encoded mapping of line numbers to bytecode indices
         co_name             name with which this code object was defined
         co_names            tuple of names other than arguments and function locals
         co_nlocals          number of local variables
@@ -1707,6 +1708,7 @@ def getframeinfo(frame, context=1):
 
 def getlineno(frame):
     """Get the line number from a frame object, allowing for optimization."""
+    # FrameType.f_lineno is now a descriptor that grovels co_lnotab
     return frame.f_lineno
 
 _FrameInfo = namedtuple('_FrameInfo', ('frame',) + Traceback._fields)

Lib/pydoc_data/topics.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-# Autogenerated by Sphinx on Mon Feb 13 10:21:05 2023
+# Autogenerated by Sphinx on Tue Feb  7 13:18:04 2023
 topics = {'assert': 'The "assert" statement\n'
            '**********************\n'
            '\n'
@@ -13704,10 +13704,13 @@
           '      bytecode; "co_filename" is the filename from which the code '
           'was\n'
           '      compiled; "co_firstlineno" is the first line number of the\n'
-          '      function; "co_stacksize" is the required stack size; '
-          '"co_flags"\n'
-          '      is an integer encoding a number of flags for the '
-          'interpreter.\n'
+          '      function; "co_lnotab" is a string encoding the mapping from\n'
+          '      bytecode offsets to line numbers (for details see the source\n'
+          '      code of the interpreter); "co_stacksize" is the required '
+          'stack\n'
+          '      size; "co_flags" is an integer encoding a number of flags '
+          'for\n'
+          '      the interpreter.\n'
           '\n'
           '      The following flag bits are defined for "co_flags": bit '
           '"0x04"\n'

Misc/gdbinit

@@ -54,7 +54,25 @@ end
 # A rewrite of the Python interpreter's line number calculator in GDB's
 # command language
 define lineno
-    printf "%d", f->f_lineno
+    set $__continue = 1
+    set $__co = f->f_code
+    set $__lasti = f->f_lasti
+    set $__sz = ((PyVarObject *)$__co->co_lnotab)->ob_size/2
+    set $__p = (unsigned char *)((PyBytesObject *)$__co->co_lnotab)->ob_sval
+    set $__li = $__co->co_firstlineno
+    set $__ad = 0
+    while ($__sz-1 >= 0 && $__continue)
+      set $__sz = $__sz - 1
+      set $__ad = $__ad + *$__p
+      set $__p = $__p + 1
+      if ($__ad > $__lasti)
+	set $__continue = 0
+      else
+        set $__li = $__li + *$__p
+        set $__p = $__p + 1
+      end
+    end
+    printf "%d", $__li
 end
 
 define pyframev

Objects/codeobject.c

@@ -1097,6 +1097,77 @@ _PyLineTable_NextAddressRange(PyCodeAddressRange *range)
     return 1;
 }
 
+static int
+emit_pair(PyObject **bytes, int *offset, int a, int b)
+{
+    Py_ssize_t len = PyBytes_GET_SIZE(*bytes);
+    if (*offset + 2 >= len) {
+        if (_PyBytes_Resize(bytes, len * 2) < 0)
+            return 0;
+    }
+    unsigned char *lnotab = (unsigned char *) PyBytes_AS_STRING(*bytes);
+    lnotab += *offset;
+    *lnotab++ = a;
+    *lnotab++ = b;
+    *offset += 2;
+    return 1;
+}
+
+static int
+emit_delta(PyObject **bytes, int bdelta, int ldelta, int *offset)
+{
+    while (bdelta > 255) {
+        if (!emit_pair(bytes, offset, 255, 0)) {
+            return 0;
+        }
+        bdelta -= 255;
+    }
+    while (ldelta > 127) {
+        if (!emit_pair(bytes, offset, bdelta, 127)) {
+            return 0;
+        }
+        bdelta = 0;
+        ldelta -= 127;
+    }
+    while (ldelta < -128) {
+        if (!emit_pair(bytes, offset, bdelta, -128)) {
+            return 0;
+        }
+        bdelta = 0;
+        ldelta += 128;
+    }
+    return emit_pair(bytes, offset, bdelta, ldelta);
+}
+
+static PyObject *
+decode_linetable(PyCodeObject *code)
+{
+    PyCodeAddressRange bounds;
+    PyObject *bytes;
+    int table_offset = 0;
+    int code_offset = 0;
+    int line = code->co_firstlineno;
+    bytes = PyBytes_FromStringAndSize(NULL, 64);
+    if (bytes == NULL) {
+        return NULL;
+    }
+    _PyCode_InitAddressRange(code, &bounds);
+    while (_PyLineTable_NextAddressRange(&bounds)) {
+        if (bounds.opaque.computed_line != line) {
+            int bdelta = bounds.ar_start - code_offset;
+            int ldelta = bounds.opaque.computed_line - line;
+            if (!emit_delta(&bytes, bdelta, ldelta, &table_offset)) {
+                Py_DECREF(bytes);
+                return NULL;
+            }
+            code_offset = bounds.ar_start;
+            line = bounds.opaque.computed_line;
+        }
+    }
+    _PyBytes_Resize(&bytes, table_offset);
+    return bytes;
+}
+
 
 typedef struct {
     PyObject_HEAD
@@ -1810,6 +1881,12 @@ static PyMemberDef code_memberlist[] = {
 };
 
 
+static PyObject *
+code_getlnotab(PyCodeObject *code, void *closure)
+{
+    return decode_linetable(code);
+}
+
 static PyObject *
 code_getvarnames(PyCodeObject *code, void *closure)
 {
@@ -1842,6 +1919,7 @@ code_getcode(PyCodeObject *code, void *closure)
 }
 
 static PyGetSetDef code_getsetlist[] = {
+    {"co_lnotab",         (getter)code_getlnotab,       NULL, NULL},
     {"_co_code_adaptive", (getter)code_getcodeadaptive, NULL, NULL},
     // The following old names are kept for backward compatibility.
     {"co_varnames",       (getter)code_getvarnames,     NULL, NULL},