Re: [GSoC] Interest and initial proposal for project on reimplementing cpychecker as -fanalyzer plugin

[Sun Steven <StevenSun2021@hotmail.com>]

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Hi, Eric, Malcom,

Sorry that I didn't check this thread before.

It sounds like there are a lot of things to do. I want to offer some help.

Let me add some backgrounds of memory management in python here.


## Intro (for people unfamiliar with CPython)

Unlike programs written in C++, where the compiler automatically adds
destructors on all exit paths, CPython requires manual memory management
on PyObject*.

The current CPython has 2 major memory management mechanisms,
including reference counting and a mark-and-sweep gc for cyclic references.
The former acts as the major mechanism. PyObject gets destructed when
the refcount drops to zero.

## CPython has made great efforts to reduce memory errors.

With specific compile flags on, the CPython interpreter records the total
refcount, also it aborts when refcount drops below zero (being double freed).
This helps to discover memory leaks. PEP 683 (implemented in 3.12) also
introduced "immortal objects" with initial refcount 999999999, prevent it from
being accidentally freed (such as small integers).

Even with these features, CPython extension management is still a problem,
since most errors occur on "error-handling path", which is less likely to be
covered. And most users will not use a debug-build cpython, making the error
more under the surface.

## Why I want to participate in?

I am currently working on the initial implementations of PEP 701 (a new
f-string​ parser). During the testing, I discovered (and fixed) 3 memory leaks.
As you can see, even the most experienced CPython developers sometimes
forget to properly decrease refs. I think it will be inspiring if a new analysis
tool was made available as a compiler builtin. It will lead to a better CPython.


I do not know if GSoC allows collaborations. Maybe the headcount is limited,
or maybe I am too senior for GSoC. But I think I am still a rookie in front of
GCC.


I want to contribute, no matter the forms.

Yours