[issue28870] Reduce stack consumption of PyObject_CallFunctionObjArgs() and like

[STINNER Victor]

STINNER Victor added the comment:

Stack used by each C function of test_python_call.

3.4:

(a) method_call: 64

(b) PyObject_Call: 48
(b) function_call: 160
(b) PyEval_EvalCodeEx: 176

(c) PyEval_EvalFrameEx: 256
(c) call_function: 0
(c) do_call: 0
(c) PyObject_Call: 48

(d) slot_tp_call: 64
(d) PyObject_Call: 48

=> total: 864


default:

(a) method_call: 80

(b) _PyObject_FastCallDict: 64
(b) _PyFunction_FastCallDict: 208
(b) _PyEval_EvalCodeWithName: 176

(c) _PyEval_EvalFrameDefault: 320
(c) call_function: 80
(c) _PyObject_FastCallKeywords: 80

(d) slot_tp_call: 64
(d) PyObject_Call: 48

=> total: 1120


Groups of functions, 3.4 => default:

(a) 64 => 80 (+16)
(b) 384 => 448 (+64)
(c) 304 => 480 (+176)
(d) 112 => 112 (=)


I used gdb:

(gdb) set $last=0
(gdb) define size
> print $last - (uintptr_t)$rsp
> set $last = (uintptr_t)$rsp
> down
(gdb) up
(gdb) up
(gdb) up
(... until a first method_call ...)
(gdb) size
(gdb) size
...

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<http://bugs.python.org/issue28870>
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