This is the implementation of PEP683
Motivation:
The PR introduces the ability to immortalize instances in CPython which bypasses reference counting. Tagging objects as immortal allows up to skip certain operations when we know that the object will be around for the entire execution of the runtime.
Note that this by itself will bring a performance regression to the runtime due to the extra reference count checks. However, this brings the ability of having truly immutable objects that are useful in other contexts such as immutable data sharing between sub-interpreters.
* The majority of the monitoring code is in instrumentation.c
* The new instrumentation bytecodes are in bytecodes.c
* legacy_tracing.c adapts the new API to the old sys.setrace and sys.setprofile APIs
* Rename local variables, names and consts, from the interpeter loop. Will allow non-code objects in frames for better introspection of C builtins and extensions.
* Remove unused dummy variables.
This change is almost entirely moving code around and hiding import state behind internal API. We introduce no changes to behavior, nor to non-internal API. (Since there was already going to be a lot of churn, I took this as an opportunity to re-organize import.c into topically-grouped sections of code.) The motivation is to simplify a number of upcoming changes.
Specific changes:
* move existing import-related code to import.c, wherever possible
* add internal API for interacting with import state (both global and per-interpreter)
* use only API outside of import.c (to limit churn there when changing the location, etc.)
* consolidate the import-related state of PyInterpreterState into a single struct field (this changes layout slightly)
* add macros for import state in import.c (to simplify changing the location)
* group code in import.c into sections
*remove _PyState_AddModule()
https://github.com/python/cpython/issues/101758
* Make sure that the current exception is always normalized.
* Remove redundant type and traceback fields for the current exception.
* Add new API functions: PyErr_GetRaisedException, PyErr_SetRaisedException
* Add new API functions: PyException_GetArgs, PyException_SetArgs
* Adds EXIT_INTERPRETER instruction to exit PyEval_EvalDefault()
* Simplifies RETURN_VALUE, YIELD_VALUE and RETURN_GENERATOR instructions as they no longer need to check for entry frames.
The switch cases (really TARGET(opcode) macros) have been moved from ceval.c to generated_cases.c.h. That file is generated from instruction definitions in bytecodes.c (which impersonates a C file so the C code it contains can be edited without custom support in e.g. VS Code).
The code generator lives in Tools/cases_generator (it has a README.md explaining how it works). The DSL used to describe the instructions is a work in progress, described in https://github.com/faster-cpython/ideas/blob/main/3.12/interpreter_definition.md.
This is surely a work-in-progress. An easy next step could be auto-generating super-instructions.
**IMPORTANT: Merge Conflicts**
If you get a merge conflict for instruction implementations in ceval.c, your best bet is to port your changes to bytecodes.c. That file looks almost the same as the original cases, except instead of `TARGET(NAME)` it uses `inst(NAME)`, and the trailing `DISPATCH()` call is omitted (the code generator adds it automatically).
This reduces confusion between jumps at the bytecode level
(e.g. JUMPTO(), JUMPBY(), and various JUMP_*() opcodes)
and jumps in the C code (which are 'goto' statements).
Change FOR_ITER to have the same stack effect regardless of whether it branches or not.
Performance is unchanged as FOR_ITER (and specialized forms jump over the cleanup code).
Make sys.setprofile() and sys.settrace() functions reentrant. They
can no long fail with: RuntimeError("Cannot install a trace function
while another trace function is being installed").
Make _PyEval_SetTrace() and _PyEval_SetProfile() functions reentrant,
rather than detecting and rejecting reentrant calls. Only delete the
reference to function arguments once the new function is fully set,
when a reentrant call is safe. Call also _PySys_Audit() earlier.
The `}` marked with `/* End instructions */` is the end of the switch.
There is another pair of `{}` around the switch, which is vestigial
from ancient times when it was `for (;;) { switch (opcode) { ... } }`.
All `DISPATCH` macro calls should be inside that pair.
Remove the sys.getdxp() function and the Tools/scripts/analyze_dxp.py
script. DXP stands for "dynamic execution pairs". They were related
to DYNAMIC_EXECUTION_PROFILE and DXPAIRS macros which have been
removed in Python 3.11. Python can now be built with "./configure
--enable-pystats" to gather statistics on Python opcodes.
Eddie Elizondo
Nikita Sobolev
Mark Shannon
Irit Katriel
Petr Viktorin
Owain Davies
Steve Dower
Eclips4
Eric Snow
Guido van Rossum
Matthieu Dartiailh
Kumar Aditya
Brandt Bucher
Skip Montanaro
Victor Stinner
Dennis Sweeney
Pablo Galindo Salgado
Carl Meyer
serge-sans-paille
adphrost