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bpo-42197: Don't create f_locals dictionary unless we actually need it. #32055

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Merged
markshannon merged 14 commits into from
Mar 25, 2022
Merged

bpo-42197: Don't create f_locals dictionary unless we actually need it. #32055

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62be414
`PyFrame_FastToLocalsWithError` and `PyFrame_LocalsToFast` are no lon…
markshannon Mar 22, 2022
d775a87
Fix formatting of news item.
markshannon Mar 22, 2022
4bc0707
Make accesses to a frame's `f_locals` safe from C code, not relying o…
markshannon Mar 23, 2022
4cf7efa
Remove unnecessary check for CO_NEWLOCALS flag.
markshannon Mar 23, 2022
d41f7ea
Remove empty line
markshannon Mar 23, 2022
723f354
Update 'what's new'
markshannon Mar 23, 2022
02f061a
Use nicer formatting
markshannon Mar 23, 2022
281305b
Fix formatting
markshannon Mar 23, 2022
8d3c911
Update Misc/NEWS.d/next/Core and Builtins/2022-03-22-15-12-28.bpo-421…
markshannon Mar 23, 2022
56aa001
Merge branch 'main' into dont-call-fasttolocals-all-the-time
markshannon Mar 23, 2022
0e452a1
Document new `PyFrame_GetLocals` C-API function.
markshannon Mar 23, 2022
65a7904
Fix up docs.
markshannon Mar 25, 2022
c017590
Make sure that modification to frame.f_locals outside of trace functi…
markshannon Mar 25, 2022
70a5717
Add whatsnew section for debugger access to f_locals.
markshannon Mar 25, 2022
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Make accesses to a frame's f_locals safe from C code, not relying o… 
…n calls to `PyFrame_FastToLocals` or `PyFrame_LocalsToFast`.
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@markshannon
markshannon committed Mar 23, 2022
commit 4bc0707bfb72362fd154e07093293d2071f066c3
1 change: 1 addition & 0 deletions Include/cpython/frameobject.h
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Expand Up @@ -23,3 +23,4 @@ PyAPI_FUNC(int) PyFrame_FastToLocalsWithError(PyFrameObject *f);
PyAPI_FUNC(void) PyFrame_FastToLocals(PyFrameObject *);

PyAPI_FUNC(PyFrameObject *) PyFrame_GetBack(PyFrameObject *frame);
PyAPI_FUNC(PyObject *) PyFrame_GetLocals(PyFrameObject *frame);
1 change: 1 addition & 0 deletions Include/internal/pycore_frame.h
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Expand Up @@ -15,6 +15,7 @@ struct _frame {
int f_lineno; /* Current line number. Only valid if non-zero */
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? */
/* The frame data, if this frame object owns the frame */
PyObject *_f_frame_data[1];
};
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4 changes: 1 addition & 3 deletions Misc/NEWS.d/next/Core and Builtins/2022-03-22-15-12-28.bpo-42197.SwrrFO.rst
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@@ -1,5 +1,3 @@
``PyFrame_FastToLocalsWithError`` and ``PyFrame_LocalsToFast`` are no longer
called during profile nor tracing. C code that accesses the ``f_locals`` attribute
directly (which is not recommended) must now call
``PyFrame_FastToLocalsWithError`` to update locals and ``PyFrame_LocalsToFast``
after ``f_locals`` are updated.
directly must do so by calling ``PyFrame_GetLocals``.
29 changes: 23 additions & 6 deletions Objects/frameobject.c
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Expand Up @@ -840,6 +840,7 @@ _PyFrame_New_NoTrack(PyCodeObject *code)
f->f_trace = NULL;
f->f_trace_lines = 1;
f->f_trace_opcodes = 0;
f->f_fast_as_locals = 0;
f->f_lineno = 0;
return f;
}
Expand Down Expand Up @@ -911,6 +912,9 @@ _PyFrame_FastToLocalsWithError(_PyInterpreterFrame *frame) {
PyObject **fast;
PyCodeObject *co;
locals = frame->f_locals;
if ((frame->f_code->co_flags & CO_NEWLOCALS) == 0) {
return 0;
}
if (locals == NULL) {
locals = frame->f_locals = PyDict_New();
if (locals == NULL)
Expand Down Expand Up @@ -1004,7 +1008,11 @@ PyFrame_FastToLocalsWithError(PyFrameObject *f)
PyErr_BadInternalCall();
return -1;
}
return _PyFrame_FastToLocalsWithError(f->f_frame);
int err = _PyFrame_FastToLocalsWithError(f->f_frame);
if (err == 0) {
f->f_fast_as_locals = 1;
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}
return err;
}

void
Expand All @@ -1028,8 +1036,12 @@ _PyFrame_LocalsToFast(_PyInterpreterFrame *frame, int clear)
PyObject *error_type, *error_value, *error_traceback;
PyCodeObject *co;
locals = frame->f_locals;
if (locals == NULL)
if ((frame->f_code->co_flags & CO_NEWLOCALS) == 0) {
return;
}
if (locals == NULL) {
return;
}
fast = _PyFrame_GetLocalsArray(frame);
co = frame->f_code;

Expand Down Expand Up @@ -1088,13 +1100,12 @@ _PyFrame_LocalsToFast(_PyInterpreterFrame *frame, int clear)
void
PyFrame_LocalsToFast(PyFrameObject *f, int clear)
{
if (f == NULL || _PyFrame_GetState(f) == FRAME_CLEARED) {
return;
if (f && f->f_fast_as_locals && _PyFrame_GetState(f) != FRAME_CLEARED) {
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_PyFrame_LocalsToFast(f->f_frame, clear);
f->f_fast_as_locals = 0;
}
_PyFrame_LocalsToFast(f->f_frame, clear);
}


PyCodeObject *
PyFrame_GetCode(PyFrameObject *frame)
{
Expand All @@ -1118,6 +1129,12 @@ PyFrame_GetBack(PyFrameObject *frame)
return back;
}

PyObject*
PyFrame_GetLocals(PyFrameObject *frame)
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{
return frame_getlocals(frame, NULL);
}

PyObject*
_PyEval_BuiltinsFromGlobals(PyThreadState *tstate, PyObject *globals)
{
Expand Down
5 changes: 5 additions & 0 deletions Python/sysmodule.c
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Expand Up @@ -933,6 +933,11 @@ call_trampoline(PyThreadState *tstate, PyObject* callback,
/* call the Python-level function */
PyObject *result = _PyObject_FastCallTstate(tstate, callback, stack, 3);

PyFrame_LocalsToFast(frame, 1);

if (result == NULL) {
PyTraceBack_Here(frame);
}

return result;
}
Expand Down