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bpo-46841: Don't scan backwards in bytecode. #31901

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Merged
merged 2 commits into from
Mar 16, 2022
Merged

bpo-46841: Don't scan backwards in bytecode. #31901

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1d67c85
Don't scan backwards in bytecode when looking for execution context.
markshannon Mar 15, 2022
1ce3c67
Merge branch 'main' into no-backward-scanning
brandtbucher Mar 15, 2022
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7 changes: 5 additions & 2 deletions Objects/genobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -359,9 +359,12 @@ _PyGen_yf(PyGenObject *gen)
assert(code[0] != SEND);
return NULL;
}

if (code[(frame->f_lasti-1)*sizeof(_Py_CODEUNIT)] != SEND || frame->stacktop < 0)
int opcode = code[(frame->f_lasti+1)*sizeof(_Py_CODEUNIT)];
int oparg = code[(frame->f_lasti+1)*sizeof(_Py_CODEUNIT)+1];
if (opcode != RESUME || oparg < 2) {
/* Not in a yield from */
return NULL;
}
yf = _PyFrame_StackPeek(frame);
Py_INCREF(yf);
}
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20 changes: 7 additions & 13 deletions Python/ceval.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1565,16 +1565,6 @@ trace_function_exit(PyThreadState *tstate, _PyInterpreterFrame *frame, PyObject
return 0;
}

static int
skip_backwards_over_extended_args(PyCodeObject *code, int offset)
{
_Py_CODEUNIT *instrs = (_Py_CODEUNIT *)PyBytes_AS_STRING(code->co_code);
while (offset > 0 && _Py_OPCODE(instrs[offset-1]) == EXTENDED_ARG) {
offset--;
}
return offset;
}

static _PyInterpreterFrame *
pop_frame(PyThreadState *tstate, _PyInterpreterFrame *frame)
{
Expand Down Expand Up @@ -5443,7 +5433,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
#else
case DO_TRACING: {
#endif
int instr_prev = skip_backwards_over_extended_args(frame->f_code, frame->f_lasti);
int instr_prev = frame->f_lasti;
frame->f_lasti = INSTR_OFFSET();
TRACING_NEXTOPARG();
if (opcode == RESUME) {
Expand Down Expand Up @@ -6725,9 +6715,13 @@ maybe_call_line_trace(Py_tracefunc func, PyObject *obj,
then call the trace function if we're tracing source lines.
*/
initialize_trace_info(&tstate->trace_info, frame);
_Py_CODEUNIT prev = ((_Py_CODEUNIT *)PyBytes_AS_STRING(frame->f_code->co_code))[instr_prev];
int entry_point = 0;
_Py_CODEUNIT *code = (_Py_CODEUNIT *)PyBytes_AS_STRING(frame->f_code->co_code);
while (_Py_OPCODE(code[entry_point]) != RESUME) {
entry_point++;
}
int lastline;
if (_Py_OPCODE(prev) == RESUME && _Py_OPARG(prev) == 0) {
if (instr_prev <= entry_point) {
lastline = -1;
}
else {
Expand Down