GH-103082: Filter LINE events in VM, to simplify tool implementation. (GH-104387)

When monitoring LINE events, instrument all instructions that can have a predecessor on a different line.
Then check that the a new line has been hit in the instrumentation code.
This brings the behavior closer to that of 3.11, simplifying implementation and porting of tools.

Author: markshannon

Include/internal/pycore_frame.h

@@ -19,7 +19,6 @@ struct _frame {
     struct _PyInterpreterFrame *f_frame; /* points to the frame data */
     PyObject *f_trace;          /* Trace function */
     int f_lineno;               /* Current line number. Only valid if non-zero */
-    int f_last_traced_line;     /* The last line traced for this frame */
     char f_trace_lines;         /* Emit per-line trace events? */
     char f_trace_opcodes;       /* Emit per-opcode trace events? */
     char f_fast_as_locals;      /* Have the fast locals of this frame been converted to a dict? */

Include/internal/pycore_instruments.h

@@ -69,13 +69,13 @@ _Py_call_instrumentation(PyThreadState *tstate, int event,
 
 extern int
 _Py_call_instrumentation_line(PyThreadState *tstate, _PyInterpreterFrame* frame,
-                              _Py_CODEUNIT *instr);
+                              _Py_CODEUNIT *instr, _Py_CODEUNIT *prev);
 
 extern int
 _Py_call_instrumentation_instruction(
     PyThreadState *tstate, _PyInterpreterFrame* frame, _Py_CODEUNIT *instr);
 
-int
+_Py_CODEUNIT *
 _Py_call_instrumentation_jump(
     PyThreadState *tstate, int event,
     _PyInterpreterFrame *frame, _Py_CODEUNIT *instr, _Py_CODEUNIT *target);
@@ -100,6 +100,7 @@ extern int
 _Py_Instrumentation_GetLine(PyCodeObject *code, int index);
 
 extern PyObject _PyInstrumentation_MISSING;
+extern PyObject _PyInstrumentation_DISABLE;
 
 #ifdef __cplusplus
 }

Lib/test/test_monitoring.py

@@ -524,7 +524,7 @@ def test_lines_loop(self):
             sys.monitoring.set_events(TEST_TOOL, 0)
             sys.monitoring.register_callback(TEST_TOOL, E.LINE, None)
             start = LineMonitoringTest.test_lines_loop.__code__.co_firstlineno
-            self.assertEqual(events, [start+7, 21, 22, 22, 21, start+8])
+            self.assertEqual(events, [start+7, 21, 22, 21, 22, 21, start+8])
         finally:
             sys.monitoring.set_events(TEST_TOOL, 0)
             sys.monitoring.register_callback(TEST_TOOL, E.LINE, None)
@@ -1050,6 +1050,8 @@ def func3():
 def line_from_offset(code, offset):
     for start, end, line in code.co_lines():
         if start <= offset < end:
+            if line is None:
+                return f"[offset={offset}]"
             return line - code.co_firstlineno
     return -1
 
@@ -1072,9 +1074,20 @@ class BranchRecorder(JumpRecorder):
     event_type = E.BRANCH
     name = "branch"
 
+class ReturnRecorder:
+
+    event_type = E.PY_RETURN
+
+    def __init__(self, events):
+        self.events = events
+
+    def __call__(self, code, offset, val):
+        self.events.append(("return", val))
+
 
 JUMP_AND_BRANCH_RECORDERS = JumpRecorder, BranchRecorder
 JUMP_BRANCH_AND_LINE_RECORDERS = JumpRecorder, BranchRecorder, LineRecorder
+FLOW_AND_LINE_RECORDERS = JumpRecorder, BranchRecorder, LineRecorder, ExceptionRecorder, ReturnRecorder
 
 class TestBranchAndJumpEvents(CheckEvents):
     maxDiff = None
@@ -1098,7 +1111,6 @@ def func():
             ('jump', 'func', 4, 2),
             ('branch', 'func', 2, 2)])
 
-
         self.check_events(func, recorders = JUMP_BRANCH_AND_LINE_RECORDERS, expected = [
             ('line', 'check_events', 10),
             ('line', 'func', 1),
@@ -1108,15 +1120,62 @@ def func():
             ('branch', 'func', 3, 6),
             ('line', 'func', 6),
             ('jump', 'func', 6, 2),
+            ('line', 'func', 2),
             ('branch', 'func', 2, 2),
             ('line', 'func', 3),
             ('branch', 'func', 3, 4),
             ('line', 'func', 4),
             ('jump', 'func', 4, 2),
+            ('line', 'func', 2),
             ('branch', 'func', 2, 2),
+            ('line', 'check_events', 11)])
+
+    def test_except_star(self):
+
+        class Foo:
+            def meth(self):
+                pass
+
+        def func():
+            try:
+                try:
+                    raise KeyError
+                except* Exception as e:
+                    f = Foo(); f.meth()
+            except KeyError:
+                pass
+
+
+        self.check_events(func, recorders = JUMP_BRANCH_AND_LINE_RECORDERS, expected = [
+            ('line', 'check_events', 10),
+            ('line', 'func', 1),
             ('line', 'func', 2),
+            ('line', 'func', 3),
+            ('line', 'func', 4),
+            ('branch', 'func', 4, 4),
+            ('line', 'func', 5),
+            ('line', 'meth', 1),
+            ('jump', 'func', 5, 5),
+            ('jump', 'func', 5, '[offset=114]'),
+            ('branch', 'func', '[offset=120]', '[offset=122]'),
             ('line', 'check_events', 11)])
 
+        self.check_events(func, recorders = FLOW_AND_LINE_RECORDERS, expected = [
+            ('line', 'check_events', 10),
+            ('line', 'func', 1),
+            ('line', 'func', 2),
+            ('line', 'func', 3),
+            ('raise', KeyError),
+            ('line', 'func', 4),
+            ('branch', 'func', 4, 4),
+            ('line', 'func', 5),
+            ('line', 'meth', 1),
+            ('return', None),
+            ('jump', 'func', 5, 5),
+            ('jump', 'func', 5, '[offset=114]'),
+            ('branch', 'func', '[offset=120]', '[offset=122]'),
+            ('return', None),
+            ('line', 'check_events', 11)])
 
 class TestSetGetEvents(MonitoringTestBase, unittest.TestCase):
 

Lib/test/test_pdb.py

@@ -1793,8 +1793,9 @@ def test_pdb_issue_gh_101517():
     ...     'continue'
     ... ]):
     ...    test_function()
-    > <doctest test.test_pdb.test_pdb_issue_gh_101517[0]>(5)test_function()
-    -> import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
+    --Return--
+    > <doctest test.test_pdb.test_pdb_issue_gh_101517[0]>(None)test_function()->None
+    -> Warning: lineno is None
     (Pdb) continue
     """
 

Lib/test/test_sys.py

@@ -1446,7 +1446,7 @@ class C(object): pass
         def func():
             return sys._getframe()
         x = func()
-        check(x, size('3Pii3c7P2ic??2P'))
+        check(x, size('3Pi3c7P2ic??2P'))
         # function
         def func(): pass
         check(func, size('14Pi'))

Lib/test/test_sys_settrace.py

@@ -2867,6 +2867,5 @@ def func(arg = 1):
         sys.settrace(None)
 
 
-
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Core and Builtins/2023-05-10-20-52-29.gh-issue-103082.y3LG5Q.rst

@@ -0,0 +1,5 @@
+Change behavior of ``sys.monitoring.events.LINE`` events in
+``sys.monitoring``: Line events now occur when a new line is reached
+dynamically, instead of using a static approximation, as before. This makes
+the behavior very similar to that of "line" events in ``sys.settrace``. This
+should ease porting of tools from 3.11 to 3.12.

Objects/frameobject.c

@@ -831,7 +831,6 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno, void *Py_UNUSED(ignore
         start_stack = pop_value(start_stack);
     }
     /* Finally set the new lasti and return OK. */
-    f->f_last_traced_line = new_lineno;
     f->f_lineno = 0;
     f->f_frame->prev_instr = _PyCode_CODE(f->f_frame->f_code) + best_addr;
     return 0;
@@ -854,7 +853,6 @@ frame_settrace(PyFrameObject *f, PyObject* v, void *closure)
     }
     if (v != f->f_trace) {
         Py_XSETREF(f->f_trace, Py_XNewRef(v));
-        f->f_last_traced_line = -1;
     }
     return 0;
 }
@@ -1056,7 +1054,6 @@ _PyFrame_New_NoTrack(PyCodeObject *code)
     f->f_trace_opcodes = 0;
     f->f_fast_as_locals = 0;
     f->f_lineno = 0;
-    f->f_last_traced_line = -1;
     return f;
 }
 

Python/bytecodes.c

@@ -3288,28 +3288,6 @@ dummy_func(
             assert(oparg >= 2);
         }
 
-        inst(INSTRUMENTED_LINE, ( -- )) {
-            _Py_CODEUNIT *here = next_instr-1;
-            _PyFrame_SetStackPointer(frame, stack_pointer);
-            int original_opcode = _Py_call_instrumentation_line(
-                    tstate, frame, here);
-            stack_pointer = _PyFrame_GetStackPointer(frame);
-            if (original_opcode < 0) {
-                next_instr = here+1;
-                goto error;
-            }
-            next_instr = frame->prev_instr;
-            if (next_instr != here) {
-                DISPATCH();
-            }
-            if (_PyOpcode_Caches[original_opcode]) {
-                _PyBinaryOpCache *cache = (_PyBinaryOpCache *)(next_instr+1);
-                INCREMENT_ADAPTIVE_COUNTER(cache->counter);
-            }
-            opcode = original_opcode;
-            DISPATCH_GOTO();
-        }
-
         inst(INSTRUMENTED_INSTRUCTION, ( -- )) {
             int next_opcode = _Py_call_instrumentation_instruction(
                 tstate, frame, next_instr-1);

Python/ceval.c

@@ -775,6 +775,41 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
 
 #include "generated_cases.c.h"
 
+    /* INSTRUMENTED_LINE has to be here, rather than in bytecodes.c,
+     * because it needs to capture frame->prev_instr before it is updated,
+     * as happens in the standard instruction prologue.
+     */
+#if USE_COMPUTED_GOTOS
+        TARGET_INSTRUMENTED_LINE:
+#else
+        case INSTRUMENTED_LINE:
+#endif
+    {
+        _Py_CODEUNIT *prev = frame->prev_instr;
+        _Py_CODEUNIT *here = frame->prev_instr = next_instr;
+        _PyFrame_SetStackPointer(frame, stack_pointer);
+        int original_opcode = _Py_call_instrumentation_line(
+                tstate, frame, here, prev);
+        stack_pointer = _PyFrame_GetStackPointer(frame);
+        if (original_opcode < 0) {
+            next_instr = here+1;
+            goto error;
+        }
+        next_instr = frame->prev_instr;
+        if (next_instr != here) {
+            DISPATCH();
+        }
+        if (_PyOpcode_Caches[original_opcode]) {
+            _PyBinaryOpCache *cache = (_PyBinaryOpCache *)(next_instr+1);
+            /* Prevent the underlying instruction from specializing
+             * and overwriting the instrumentation. */
+            INCREMENT_ADAPTIVE_COUNTER(cache->counter);
+        }
+        opcode = original_opcode;
+        DISPATCH_GOTO();
+    }
+
+
 #if USE_COMPUTED_GOTOS
         _unknown_opcode:
 #else

Python/ceval_macros.h

@@ -334,11 +334,10 @@ do { \
 #define INSTRUMENTED_JUMP(src, dest, event) \
 do { \
     _PyFrame_SetStackPointer(frame, stack_pointer); \
-    int err = _Py_call_instrumentation_jump(tstate, event, frame, src, dest); \
+    next_instr = _Py_call_instrumentation_jump(tstate, event, frame, src, dest); \
     stack_pointer = _PyFrame_GetStackPointer(frame); \
-    if (err) { \
+    if (next_instr == NULL) { \
         next_instr = (dest)+1; \
         goto error; \
     } \
-    next_instr = frame->prev_instr; \
 } while (0);