[Bug analyzer/107646] RFE: can we reimplement gcc-python-plugin's cpychecker as a -fanalyzer plugin?

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107646

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Eric Feng <efric@gcc.gnu.org>:

https://gcc.gnu.org/g:38c00edd65c39b07166aa0913c79adb9bcac943c

commit r14-3162-g38c00edd65c39b07166aa0913c79adb9bcac943c
Author: Eric Feng <ef2648@columbia.edu>
Date:   Fri Aug 11 12:30:43 2023 -0400

    analyzer: More features for CPython analyzer plugin [PR107646]

    This patch adds known function subclasses for Python/C API functions
    PyList_New, PyLong_FromLong, and PyList_Append. It also adds new
    optional parameters for
    region_model::get_or_create_region_for_heap_alloc, allowing for the
    newly allocated region to immediately transition from the start state to
    the assumed non-null state in the malloc state machine if desired.
    Finally, it adds a new procedure, dg-require-python-h, intended as a
    directive in Python-related analyzer tests, to append necessary Python
    flags during the tests' build process.

    The main warnings we gain in this patch with respect to the known function
    subclasses mentioned are leak related. For example:

    rc3.c: In function âcreate_py_objectâ:
    â
    rc3.c:21:10: warning: leak of âitemâ [CWE-401] [-Wanalyzer-malloc-leak]
    â
       21 |   return list;
          â
          |          ^~~~
    â
      âcreate_py_objectâ: events 1-4
    â
        |
    â
        |    4 |   PyObject* item = PyLong_FromLong(10);
    â
        |      |                    ^~~~~~~~~~~~~~~~~~~
    â
        |      |                    |
    â
        |      |                    (1) allocated here
    â
        |      |                    (2) when âPyLong_FromLongâ succeeds
    â
        |    5 |   PyObject* list = PyList_New(2);
    â
        |      |                    ~~~~~~~~~~~~~
    â
        |      |                    |
    â
        |      |                    (3) when âPyList_Newâ fails
    â
        |......
    â
        |   21 |   return list;
    â
        |      |          ~~~~
    â
        |      |          |
    â
        |      |          (4) âitemâ leaks here; was allocated at (1)
    â

    Some concessions were made to
    simplify the analysis process when comparing kf_PyList_Append with the
    real implementation. In particular, PyList_Append performs some
    optimization internally to try and avoid calls to realloc if
    possible. For simplicity, we assume that realloc is called every time.
    Also, we grow the size by just 1 (to ensure enough space for adding a
    new element) rather than abide by the heuristics that the actual
implementation
    follows.

    gcc/analyzer/ChangeLog:
            PR analyzer/107646
            * call-details.h: New function.
            * region-model.cc
(region_model::get_or_create_region_for_heap_alloc):
            New optional parameters.
            * region-model.h (class region_model): New optional parameters.
            * sm-malloc.cc (on_realloc_with_move): New function.
            (region_model::transition_ptr_sval_non_null): New function.

    gcc/testsuite/ChangeLog:
            PR analyzer/107646
            * gcc.dg/plugin/analyzer_cpython_plugin.c: Analyzer support for
            PyList_New, PyList_Append, PyLong_FromLong
            * gcc.dg/plugin/plugin.exp: New test.
            * lib/target-supports.exp: New procedure.
            * gcc.dg/plugin/cpython-plugin-test-2.c: New test.

    Signed-off-by: Eric Feng <ef2648@columbia.edu>