Move creation of a tuple for var-positional parameter out of
_PyArg_UnpackKeywordsWithVararg().
Merge _PyArg_UnpackKeywordsWithVararg() with _PyArg_UnpackKeywords().
Add a new parameter in _PyArg_UnpackKeywords().
The "parameters" and "converters" attributes of ParseArgsCodeGen no
longer contain the var-positional parameter. It is now available as the
"varpos" attribute. Optimize code generation for var-positional
parameter and reuse the same generating code for functions with and without
keyword parameters.
Add special converters for var-positional parameter. "tuple" represents it as
a Python tuple and "array" represents it as a continuous array of PyObject*.
"object" is a temporary alias of "tuple".
Avoid temporary tuple creation when all arguments either positional-only
or vararg.
Objects/setobject.c and Modules/gcmodule.c adapted. This fixes slight
performance regression for set methods, introduced by gh-115112.
* Parameters after the var-positional parameter are now keyword-only
instead of positional-or-keyword.
* Correctly calculate min_kw_only.
* Raise errors for invalid combinations of the var-positional parameter
with "*", "/" and deprecation markers.
When the _Py_SINGLETON() is used, Argument Clinic now adds an
explicit "pycore_runtime.h" include to get the macro. Previously, the
macro may or may not be included indirectly by another include.
_PyArg_Parser holds static global data generated for modules by Argument Clinic. The _PyArg_Parser.kwtuple field is a tuple object, even though it's stored within a static global. In some cases the tuple is statically allocated and thus it's okay that it gets shared by multiple interpreters. However, in other cases the tuple is set lazily, allocated from the heap using the active interprepreter at the point the tuple is needed.
This is a problem once that interpreter is destroyed since _PyArg_Parser.kwtuple becomes at dangling pointer, leading to crashes. It isn't a problem if the tuple is allocated under the main interpreter, since its lifetime is bound to the lifetime of the runtime. The solution here is to temporarily switch to the main interpreter. The alternative would be to always statically allocate the tuple.
This change also fixes a bug where only the most recent parser was added to the global linked list.
