Make tracing tests work exactly as in CPython and compare the tracing results...

Make tracing tests work exactly as in CPython and compare the tracing results for both Python and Cython functions.
Fix "frame.f_trace" test in tracing code accordingly.
See #1769 and #1774 for background.

Cython/Utility/Profile.c

@@ -198,8 +198,7 @@
               PyThreadState *tstate;                                                       \
               PyGILState_STATE state = PyGILState_Ensure();                                \
               tstate = __Pyx_PyThreadState_Current;                                        \
-              if (unlikely(tstate->use_tracing && tstate->c_tracefunc                      \
-                  && __pyx_frame->f_trace != Py_None)) {                                   \
+              if (unlikely(tstate->use_tracing && tstate->c_tracefunc && $frame_cname->f_trace)) { \
                   ret = __Pyx_call_line_trace_func(tstate, $frame_cname, lineno);          \
               }                                                                            \
               PyGILState_Release(state);                                                   \
@@ -207,8 +206,7 @@
           }                                                                                \
       } else {                                                                             \
           PyThreadState* tstate = __Pyx_PyThreadState_Current;                             \
-          if (unlikely(tstate->use_tracing && tstate->c_tracefunc                          \
-                && __pyx_frame->f_trace != Py_None)) {                                     \
+          if (unlikely(tstate->use_tracing && tstate->c_tracefunc && $frame_cname->f_trace)) { \
               int ret = __Pyx_call_line_trace_func(tstate, $frame_cname, lineno);          \
               if (unlikely(ret)) goto_error;                                               \
           }                                                                                \
@@ -218,8 +216,7 @@
   #define __Pyx_TraceLine(lineno, nogil, goto_error)                                       \
   if (likely(!__Pyx_use_tracing)); else {                                                  \
       PyThreadState* tstate = __Pyx_PyThreadState_Current;                                 \
-      if (unlikely(tstate->use_tracing && tstate->c_tracefunc                              \
-                && __pyx_frame->f_trace != Py_None)) {                                     \
+      if (unlikely(tstate->use_tracing && tstate->c_tracefunc && $frame_cname->f_trace)) { \
           int ret = __Pyx_call_line_trace_func(tstate, $frame_cname, lineno);              \
           if (unlikely(ret)) goto_error;                                                   \
       }                                                                                    \

tests/run/line_trace.pyx

@@ -3,6 +3,8 @@
 # mode: run
 # tag: trace
 
+import sys
+
 from cpython.ref cimport PyObject, Py_INCREF, Py_XINCREF, Py_XDECREF
 
 cdef extern from "frameobject.h":
@@ -15,8 +17,8 @@ from cpython.pystate cimport (
     PyTrace_C_CALL, PyTrace_C_EXCEPTION, PyTrace_C_RETURN)
 
 cdef extern from *:
-    void PyEval_SetProfile(Py_tracefunc cfunc, object obj)
-    void PyEval_SetTrace(Py_tracefunc cfunc, object obj)
+    void PyEval_SetProfile(Py_tracefunc cfunc, PyObject *obj)
+    void PyEval_SetTrace(Py_tracefunc cfunc, PyObject *obj)
 
 
 map_trace_types = {
@@ -31,29 +33,40 @@ map_trace_types = {
 
 
 cdef int trace_trampoline(PyObject* _traceobj, PyFrameObject* _frame, int what, PyObject* _arg) except -1:
-    frame = <object>_frame
-    traceobj = <object>_traceobj if _traceobj else None
-    arg = <object>_arg if _arg else None
+    """
+    This is (more or less) what CPython does in sysmodule.c, function trace_trampoline().
+    """
+    cdef PyObject *tmp
 
     if what == PyTrace_CALL:
-        callback = traceobj
-    else:
+        if _traceobj is NULL:
+            return 0
+        callback = <object>_traceobj
+    elif _frame.f_trace:
         callback = <object>_frame.f_trace
-
-    if callback is None:
+    else:
         return 0
 
+    frame = <object>_frame
+    arg = <object>_arg if _arg else None
+
+    try:
         result = callback(frame, what, arg)
+    except:
+        PyEval_SetTrace(NULL, NULL)
+        tmp = _frame.f_trace
+        _frame.f_trace = NULL
+        Py_XDECREF(tmp)
+        raise
 
+    if result is not None:
         # A bug in Py2.6 prevents us from calling the Python-level setter here,
         # or otherwise we would get miscalculated line numbers. Was fixed in Py2.7.
-    cdef PyObject *tmp = _frame.f_trace
+        tmp = _frame.f_trace
         Py_INCREF(result)
         _frame.f_trace = <PyObject*>result
         Py_XDECREF(tmp)
 
-    if result is None:
-        PyEval_SetTrace(NULL, None)
     return 0
 
 
@@ -61,7 +74,7 @@ def _create_trace_func(trace):
     local_names = {}
 
     def _trace_func(frame, event, arg):
-        trace.append((map_trace_types(event), frame.f_lineno - frame.f_code.co_firstlineno))
+        trace.append((map_trace_types(event, event), frame.f_lineno - frame.f_code.co_firstlineno))
 
         lnames = frame.f_code.co_varnames
         if frame.f_code.co_name in local_names:
@@ -104,10 +117,12 @@ def _create__failing_line_trace_func(trace):
         return _trace_func
     return _trace_func
 
+
 def _create_disable_tracing(trace):
     func = _create_trace_func(trace)
     def _trace_func(frame, event, arg):
         if frame.f_lineno - frame.f_code.co_firstlineno == 2:
+            PyEval_SetTrace(NULL, NULL)
             return None
 
         func(frame, event, arg)
@@ -115,6 +130,7 @@ def _create_disable_tracing(trace):
 
     return _trace_func
 
+
 def cy_add(a,b):
     x = a + b     # 1
     return x      # 2
@@ -128,20 +144,39 @@ def cy_add_with_nogil(a,b):
     return z                     # 5
 
 
+def global_name(global_name):
+    # See GH #1836: accessing "frame.f_locals" deletes locals from globals dict.
+    return global_name + 321
+
+
 cdef int cy_add_nogil(int a, int b) nogil except -1:
     x = a + b   # 1
     return x    # 2
 
 
-def run_trace(func, *args):
+def run_trace(func, *args, bint with_sys=False):
     """
     >>> def py_add(a,b):
     ...     x = a+b
     ...     return x
+
+    >>> def py_add_with_nogil(a,b):
+    ...     x=a; y=b                     # 1
+    ...     for _ in range(1):           # 2
+    ...         z = 0                    # 3
+    ...         z += py_add(x, y)        # 4
+    ...     return z                     # 5
+
     >>> run_trace(py_add, 1, 2)
     [('call', 0), ('line', 1), ('line', 2), ('return', 2)]
     >>> run_trace(cy_add, 1, 2)
     [('call', 0), ('line', 1), ('line', 2), ('return', 2)]
+
+    >>> run_trace(py_add, 1, 2, with_sys=True)
+    [('call', 0), ('line', 1), ('line', 2), ('return', 2)]
+    >>> run_trace(cy_add, 1, 2, with_sys=True)
+    [('call', 0), ('line', 1), ('line', 2), ('return', 2)]
+
     >>> result = run_trace(cy_add_with_nogil, 1, 2)
     >>> result[:5]
     [('call', 0), ('line', 1), ('line', 2), ('line', 3), ('line', 4)]
@@ -149,13 +184,45 @@ def run_trace(func, *args):
     [('call', 0), ('line', 1), ('line', 2), ('return', 2)]
     >>> result[9:]
     [('line', 2), ('line', 5), ('return', 5)]
+
+    >>> result = run_trace(cy_add_with_nogil, 1, 2, with_sys=True)
+    >>> result[:5]  # sys
+    [('call', 0), ('line', 1), ('line', 2), ('line', 3), ('line', 4)]
+    >>> result[5:9]  # sys
+    [('call', 0), ('line', 1), ('line', 2), ('return', 2)]
+    >>> result[9:]  # sys
+    [('line', 2), ('line', 5), ('return', 5)]
+
+    >>> result = run_trace(py_add_with_nogil, 1, 2)
+    >>> result[:5]  # py
+    [('call', 0), ('line', 1), ('line', 2), ('line', 3), ('line', 4)]
+    >>> result[5:9]  # py
+    [('call', 0), ('line', 1), ('line', 2), ('return', 2)]
+    >>> result[9:]  # py
+    [('line', 2), ('line', 5), ('return', 5)]
+
+    >>> run_trace(global_name, 123)
+    [('call', 0), ('line', 2), ('return', 2)]
+    >>> run_trace(global_name, 111)
+    [('call', 0), ('line', 2), ('return', 2)]
+    >>> run_trace(global_name, 111, with_sys=True)
+    [('call', 0), ('line', 2), ('return', 2)]
+    >>> run_trace(global_name, 111, with_sys=True)
+    [('call', 0), ('line', 2), ('return', 2)]
     """
     trace = []
-    PyEval_SetTrace(<Py_tracefunc>trace_trampoline, _create_trace_func(trace))
+    trace_func = _create_trace_func(trace)
+    if with_sys:
+        sys.settrace(trace_func)
+    else:
+        PyEval_SetTrace(<Py_tracefunc>trace_trampoline, <PyObject*>trace_func)
     try:
         func(*args)
     finally:
-        PyEval_SetTrace(NULL, None)
+        if with_sys:
+            sys.settrace(None)
+        else:
+            PyEval_SetTrace(NULL, NULL)
     return trace
 
 
@@ -164,22 +231,39 @@ def fail_on_call_trace(func, *args):
     >>> def py_add(a,b):
     ...     x = a+b
     ...     return x
+
     >>> fail_on_call_trace(py_add, 1, 2)
     Traceback (most recent call last):
     ValueError: failing call trace!
+
+    >>> fail_on_call_trace(cy_add, 1, 2)
+    Traceback (most recent call last):
+    ValueError: failing call trace!
     """
     trace = []
-    PyEval_SetTrace(<Py_tracefunc>trace_trampoline, _create_failing_call_trace_func(trace))
+    trace_func = _create_failing_call_trace_func(trace)
+    PyEval_SetTrace(<Py_tracefunc>trace_trampoline, <PyObject*>trace_func)
     try:
         func(*args)
     finally:
-        PyEval_SetTrace(NULL, None)
+        PyEval_SetTrace(NULL, NULL)
     assert not trace
 
 
-def fail_on_line_trace(fail_func):
+def fail_on_line_trace(fail_func, add_func, nogil_add_func):
     """
-    >>> result = fail_on_line_trace(None)
+    >>> def py_add(a,b):
+    ...     x = a+b       # 1
+    ...     return x      # 2
+
+    >>> def py_add_with_nogil(a,b):
+    ...     x=a; y=b                     # 1
+    ...     for _ in range(1):           # 2
+    ...         z = 0                    # 3
+    ...         z += py_add(x, y)        # 4
+    ...     return z                     # 5
+
+    >>> result = fail_on_line_trace(None, cy_add, cy_add_with_nogil)
     >>> len(result)
     17
     >>> result[:5]
@@ -191,35 +275,60 @@ def fail_on_line_trace(fail_func):
     >>> result[14:]
     [('line', 2), ('line', 5), ('return', 5)]
 
-    >>> result = fail_on_line_trace('cy_add_with_nogil')
+    >>> result = fail_on_line_trace(None, py_add, py_add_with_nogil)
+    >>> len(result)
+    17
+    >>> result[:5]  # py
+    ['NO ERROR', ('call', 0), ('line', 1), ('line', 2), ('return', 2)]
+    >>> result[5:10]  # py
+    [('call', 0), ('line', 1), ('line', 2), ('line', 3), ('line', 4)]
+    >>> result[10:14]  # py
+    [('call', 0), ('line', 1), ('line', 2), ('return', 2)]
+    >>> result[14:]  # py
+    [('line', 2), ('line', 5), ('return', 5)]
+
+    >>> result = fail_on_line_trace('cy_add_with_nogil', cy_add, cy_add_with_nogil)
     failing line trace!
     >>> result
-    ['cy_add_with_nogil', ('call', 0), ('line', 1), ('line', 2), ('return', 2), ('call', 0), ('return', 1)]
+    ['cy_add_with_nogil', ('call', 0), ('line', 1), ('line', 2), ('return', 2), ('call', 0)]
 
-    >>> result = fail_on_line_trace('cy_add_nogil')
+    >>> result = fail_on_line_trace('py_add_with_nogil', py_add, py_add_with_nogil)  # py
+    failing line trace!
+    >>> result  # py
+    ['py_add_with_nogil', ('call', 0), ('line', 1), ('line', 2), ('return', 2), ('call', 0)]
+
+    >>> result = fail_on_line_trace('cy_add_nogil', cy_add, cy_add_with_nogil)
     failing line trace!
     >>> result[:5]
     ['cy_add_nogil', ('call', 0), ('line', 1), ('line', 2), ('return', 2)]
     >>> result[5:]
-    [('call', 0), ('line', 1), ('line', 2), ('line', 3), ('line', 4), ('call', 0), ('return', 1), ('return', 4)]
+    [('call', 0), ('line', 1), ('line', 2), ('line', 3), ('line', 4), ('call', 0)]
+
+    >>> result = fail_on_line_trace('py_add', py_add, py_add_with_nogil)  # py
+    failing line trace!
+    >>> result[:5]  # py
+    ['py_add', ('call', 0), ('line', 1), ('line', 2), ('return', 2)]
+    >>> result[5:]  # py
+    [('call', 0), ('line', 1), ('line', 2), ('line', 3), ('line', 4), ('call', 0)]
     """
     cdef int x = 1
     trace = ['NO ERROR']
     exception = None
-    PyEval_SetTrace(<Py_tracefunc>trace_trampoline, _create__failing_line_trace_func(trace))
+    trace_func = _create__failing_line_trace_func(trace)
+    PyEval_SetTrace(<Py_tracefunc>trace_trampoline, <PyObject*>trace_func)
     try:
         x += 1
-        cy_add(1, 2)
+        add_func(1, 2)
         x += 1
         if fail_func:
             trace[0] = fail_func  # trigger error on first line
         x += 1
-        cy_add_with_nogil(3, 4)
+        nogil_add_func(3, 4)
         x += 1
     except Exception as exc:
         exception = str(exc)
     finally:
-        PyEval_SetTrace(NULL, None)
+        PyEval_SetTrace(NULL, NULL)
     if exception:
         print(exception)
     else:
@@ -227,33 +336,37 @@ def fail_on_line_trace(fail_func):
     return trace
 
 
-def disable_trace(func, *args):
+def disable_trace(func, *args, bint with_sys=False):
     """
     >>> def py_add(a,b):
     ...     x = a+b
     ...     return x
     >>> disable_trace(py_add, 1, 2)
     [('call', 0), ('line', 1)]
+    >>> disable_trace(py_add, 1, 2, with_sys=True)
+    [('call', 0), ('line', 1)]
+
     >>> disable_trace(cy_add, 1, 2)
     [('call', 0), ('line', 1)]
+    >>> disable_trace(cy_add, 1, 2, with_sys=True)
+    [('call', 0), ('line', 1)]
+
     >>> disable_trace(cy_add_with_nogil, 1, 2)
     [('call', 0), ('line', 1)]
+    >>> disable_trace(cy_add_with_nogil, 1, 2, with_sys=True)
+    [('call', 0), ('line', 1)]
     """
     trace = []
-    PyEval_SetTrace(<Py_tracefunc>trace_trampoline, _create_disable_tracing(trace))
+    trace_func = _create_disable_tracing(trace)
+    if with_sys:
+        sys.settrace(trace_func)
+    else:
+        PyEval_SetTrace(<Py_tracefunc>trace_trampoline, <PyObject*>trace_func)
     try:
         func(*args)
     finally:
-        PyEval_SetTrace(NULL, None)
+        if with_sys:
+            sys.settrace(None)
+        else:
+            PyEval_SetTrace(NULL, NULL)
     return trace
-
-
-def global_name(global_name):
-    """
-    >>> global_name(123)
-    444
-    >>> global_name(111)
-    432
-    """
-    # See GH #1836: accessing "frame.f_locals" deletes locals from globals dict.
-    return global_name + 321