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Merged
merged 2 commits into from
Apr 6, 2021
Merged

bpo-43683: Handle generator entry in bytecode #25138

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3a41a50
Handle check for sending None to starting generator and coroutine int…
markshannon Jan 20, 2020
1a29ec3
Improve wording in NEWS item.
markshannon Apr 6, 2021
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8 changes: 8 additions & 0 deletions Doc/library/dis.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -1247,6 +1247,14 @@ All of the following opcodes use their arguments.

.. versionadded:: 3.10

.. opcode:: GEN_START (kind)

Pops TOS. If TOS was not ``None``, raises an exception. The ``kind``
operand corresponds to the type of generator or coroutine and determines
the error message. The legal kinds are 0 for generator, 1 for coroutine,
and 2 for async generator.

.. versionadded:: 3.10

.. opcode:: HAVE_ARGUMENT

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1 change: 1 addition & 0 deletions Include/opcode.h
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1 change: 1 addition & 0 deletions Lib/importlib/_bootstrap_external.py
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Expand Up @@ -315,6 +315,7 @@ def _write_atomic(path, data, mode=0o666):
# Python 3.10a2 3433 (RERAISE restores f_lasti if oparg != 0)
# Python 3.10a6 3434 (PEP 634: Structural Pattern Matching)
# Python 3.10a7 3435 Use instruction offsets (as opposed to byte offsets).
# Python 3.10a7 3436 (Add GEN_START bytecode #43683)

#
# MAGIC must change whenever the bytecode emitted by the compiler may no
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1 change: 1 addition & 0 deletions Lib/opcode.py
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Expand Up @@ -173,6 +173,7 @@ def jabs_op(name, op):
def_op('DELETE_FAST', 126) # Local variable number
haslocal.append(126)

def_op('GEN_START', 129) # Kind of generator/coroutine
def_op('RAISE_VARARGS', 130) # Number of raise arguments (1, 2, or 3)
def_op('CALL_FUNCTION', 131) # #args
def_op('MAKE_FUNCTION', 132) # Flags
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2021-04-01-12-30-30.bpo-43683.AjxOx2.rst
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@@ -0,0 +1,2 @@
Add GEN_START opcode. Marks start of generator, including async, or coroutine and handles
sending values to a newly created generator or coroutine.
27 changes: 6 additions & 21 deletions Objects/genobject.c
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Expand Up @@ -176,27 +176,12 @@ gen_send_ex2(PyGenObject *gen, PyObject *arg, PyObject **presult,
}

assert(_PyFrame_IsRunnable(f));
if (f->f_lasti == -1) {
if (arg && arg != Py_None) {
const char *msg = "can't send non-None value to a "
"just-started generator";
if (PyCoro_CheckExact(gen)) {
msg = NON_INIT_CORO_MSG;
}
else if (PyAsyncGen_CheckExact(gen)) {
msg = "can't send non-None value to a "
"just-started async generator";
}
PyErr_SetString(PyExc_TypeError, msg);
return PYGEN_ERROR;
}
} else {
/* Push arg onto the frame's value stack */
result = arg ? arg : Py_None;
Py_INCREF(result);
gen->gi_frame->f_valuestack[gen->gi_frame->f_stackdepth] = result;
gen->gi_frame->f_stackdepth++;
}
assert(f->f_lasti >= 0 || ((unsigned char *)PyBytes_AS_STRING(f->f_code->co_code))[0] == GEN_START);
/* Push arg onto the frame's value stack */
result = arg ? arg : Py_None;
Py_INCREF(result);
gen->gi_frame->f_valuestack[gen->gi_frame->f_stackdepth] = result;
gen->gi_frame->f_stackdepth++;

/* Generators always return to their most recent caller, not
* necessarily their creator. */
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24 changes: 24 additions & 0 deletions Python/ceval.c
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Expand Up @@ -2639,6 +2639,30 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)
goto exiting;
}

case TARGET(GEN_START): {
PyObject *none = POP();
Py_DECREF(none);
if (none != Py_None) {
if (oparg > 2) {
_PyErr_SetString(tstate, PyExc_SystemError,
"Illegal kind for GEN_START");
}
else {
static const char *gen_kind[3] = {
"generator",
"coroutine",
"async generator"
};
_PyErr_Format(tstate, PyExc_TypeError,
"can't send non-None value to a "
"just-started %s",
gen_kind[oparg]);
}
goto error;
}
DISPATCH();
}

case TARGET(POP_EXCEPT): {
PyObject *type, *value, *traceback;
_PyErr_StackItem *exc_info;
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47 changes: 46 additions & 1 deletion Python/compile.c
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Expand Up @@ -1140,6 +1140,8 @@ stack_effect(int opcode, int oparg, int jump)
return 1;
case LIST_TO_TUPLE:
return 0;
case GEN_START:
return -1;
case LIST_EXTEND:
case SET_UPDATE:
case DICT_MERGE:
Expand Down Expand Up @@ -6169,7 +6171,11 @@ stackdepth(struct compiler *c)
}

sp = stack;
stackdepth_push(&sp, entryblock, 0);
if (c->u->u_ste->ste_generator || c->u->u_ste->ste_coroutine) {
stackdepth_push(&sp, entryblock, 1);
} else {
stackdepth_push(&sp, entryblock, 0);
}
while (sp != stack) {
b = *--sp;
int depth = b->b_startdepth;
Expand Down Expand Up @@ -6648,6 +6654,41 @@ optimize_cfg(struct assembler *a, PyObject *consts);
static int
ensure_exits_have_lineno(struct compiler *c);

static int
insert_generator_prefix(struct compiler *c, basicblock *entryblock) {

int flags = compute_code_flags(c);
if (flags < 0) {
return -1;
}
int kind;
if (flags & (CO_GENERATOR | CO_COROUTINE | CO_ASYNC_GENERATOR)) {
if (flags & CO_COROUTINE) {
kind = 1;
}
else if (flags & CO_ASYNC_GENERATOR) {
kind = 2;
}
else {
kind = 0;
}
}
else {
return 0;
}
if (compiler_next_instr(entryblock) < 0) {
return -1;
}
for (int i = entryblock->b_iused-1; i > 0; i--) {
entryblock->b_instr[i] = entryblock->b_instr[i-1];
}
entryblock->b_instr[0].i_opcode = GEN_START;
entryblock->b_instr[0].i_oparg = kind;
entryblock->b_instr[0].i_lineno = -1;
entryblock->b_instr[0].i_target = NULL;
return 0;
}

static PyCodeObject *
assemble(struct compiler *c, int addNone)
{
Expand Down Expand Up @@ -6685,6 +6726,10 @@ assemble(struct compiler *c, int addNone)
entryblock = b;
}

if (insert_generator_prefix(c, entryblock)) {
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If we're compiling a generator (or coroutine etc.) the new function assumes (without asserting) that entryblock is not NULL. But evidently it could be, since below on line 6690 there's a check whether it could be. I don't know how it could be NULL - that would mean there's no code in the function at all, but it seems there's code above that always adds at least one instruction (RETURN_VALUE on line 6668). So maybe the check for entryblock == NULL below can be replaced by an assert? (I'd place that assert right underneath the for-loop above on lines 6683-6686.

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entryblock cannot be NULL. I'll add the assert.

goto error;
}

/* Set firstlineno if it wasn't explicitly set. */
if (!c->u->u_firstlineno) {
if (entryblock && entryblock->b_instr && entryblock->b_instr->i_lineno)
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