STINNER Victor <vstin...@python.org> added the comment:
The coverage project has a ctrace C extension which access
PyFrameObject.f_lasti which is gone in Python 3.11. It uses MyFrame_lasti()
helper to handle Python 3.10 lasti change:
---
// The f_lasti field changed meaning in 3.10.0a7. It had been bytes, but
// now is instructions, so we need to adjust it to use it as a byte index.
#if PY_VERSION_HEX >= 0x030A00A7
#define MyFrame_lasti(f) (f->f_lasti * 2)
#else
#define MyFrame_lasti(f) f->f_lasti
#endif // 3.10.0a7
---
f_lasti is used for two things in coverage/ctracer/tracer.c:
(1) get the last opcode:
----
/* Need to distinguish between RETURN_VALUE and YIELD_VALUE. Read
* the current bytecode to see what it is. In unusual circumstances
* (Cython code), co_code can be the empty string, so range-check
* f_lasti before reading the byte.
*/
int bytecode = RETURN_VALUE;
PyObject * pCode = MyFrame_GetCode(frame)->co_code;
int lasti = MyFrame_lasti(frame);
if (lasti < PyBytes_GET_SIZE(pCode)) {
bytecode = PyBytes_AS_STRING(pCode)[lasti];
}
if (bytecode != YIELD_VALUE) {
int first = MyFrame_GetCode(frame)->co_firstlineno;
if (CTracer_record_pair(self, self->pcur_entry->last_line,
-first) < 0) {
goto error;
}
}
----
(2) get the line number, with a special case for generator which is not started
yet (lasti < 0)
---
/* A call event is really a "start frame" event, and can happen for
* re-entering a generator also. f_lasti is -1 for a true call, and a
* real byte offset for a generator re-entry.
*/
if (frame->f_lasti < 0) {
self->pcur_entry->last_line = -MyFrame_GetCode(frame)->co_firstlineno;
}
else {
self->pcur_entry->last_line = PyFrame_GetLineNumber(frame);
}
---
Since Python 3.10.0a3, PyFrame_GetLineNumber() handles the case of negative
f_lasti, thanks to the commit 877df851c3ecdb55306840e247596e7b7805a60a related
to the PEP 626 implementation:
---
int
PyCode_Addr2Line(PyCodeObject *co, int addrq)
{
if (addrq < 0) {
return co->co_firstlineno;
}
...
}
---
=> coverage would need an abstraction to get the last opcode: use case (1).
I recall that an old version of asyncio also had to get latest opcode, in pure
Python, to workaround the CPython bpo-21209 bug:
+# Check for CPython issue #21209
+def has_yield_from_bug():
+ class MyGen:
+ def __init__(self):
+ self.send_args = None
+ def __iter__(self):
+ return self
+ def __next__(self):
+ return 42
+ def send(self, *what):
+ self.send_args = what
+ return None
+ def yield_from_gen(gen):
+ yield from gen
+ value = (1, 2, 3)
+ gen = MyGen()
+ coro = yield_from_gen(gen)
+ next(coro)
+ coro.send(value)
+ return gen.send_args != (value,)
+_YIELD_FROM_BUG = has_yield_from_bug()
+del has_yield_from_bug
(...)
+ if _YIELD_FROM_BUG:
+ # For for CPython issue #21209: using "yield from" and a custom
+ # generator, generator.send(tuple) unpacks the tuple instead of passing
+ # the tuple unchanged. Check if the caller is a generator using "yield
+ # from" to decide if the parameter should be unpacked or not.
+ def send(self, *value):
+ frame = sys._getframe()
+ caller = frame.f_back
+ assert caller.f_lasti >= 0
+ if caller.f_code.co_code[caller.f_lasti] != _YIELD_FROM:
+ value = value[0]
+ return self.gen.send(value)
+ else:
+ def send(self, value):
+ return self.gen.send(value)
Hopefully, this code could be be removed from asyncio, since the bug was fixed
(and asyncio is now only maintained in the Python stdlib, it's not longer a
third party module).
----------
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<https://bugs.python.org/issue40421>
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