Re: [COMMITTED] analyzer: More features for CPython analyzer plugin [PR107646]

[Eric Feng <ef2648@columbia.edu>]

I've noticed there were still some strange indentations in the last
patch ... however, I think I've finally figured out a sane formatting
solution for me (fingers crossed). I will address them in the
follow-up patch at the same time as adding more test coverage.

---

In case, anyone else using VSCode has been having issues with
formatting according to GNU/GCC conventions, these are the relevant
formatting settings that I've found work for me. Assuming the C/C++
extension is installed, then in settings.json:

"C_Cpp.clang_format_style": "{ BasedOnStyle: GNU, UseTab: Always,
TabWidth: 8, IndentWidth: 8 }"

Just setting the base style to GNU formats everything correctly except
for the fact that indentation defaults to spaces (which is what I've
been struggling with fixing manually in the last few patches). The
rest of the settings are for replacing blocks of 8 spaces with tabs
(which is a requirement in check_GNU_style). In combination, this
works for everything except for header files for some reason, but I'll
defer that battle to another day.

On Fri, Aug 11, 2023 at 1:47 PM Eric Feng <ef2648@columbia.edu> wrote:
>
> Thanks for the feedback! I've incorporated the changes (aside from
> expanding test coverage, which I plan on releasing in a follow-up),
> rebased, and performed a bootstrap and regtest on
> aarch64-unknown-linux-gnu. Since you mentioned that it is good for trunk
> with nits fixed and no problems after rebase, the patch has now been pushed.
>
> Best,
> Eric
>
> ---
>
> 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 ‘create_py_object’:
> │
> rc3.c:21:10: warning: leak of ‘item’ [CWE-401] [-Wanalyzer-malloc-leak]
> │
>    21 |   return list;
>       │
>       |          ^~~~
> │
>   ‘create_py_object’: events 1-4
> │
>     |
> │
>     |    4 |   PyObject* item = PyLong_FromLong(10);
> │
>     |      |                    ^~~~~~~~~~~~~~~~~~~
> │
>     |      |                    |
> │
>     |      |                    (1) allocated here
> │
>     |      |                    (2) when ‘PyLong_FromLong’ succeeds
> │
>     |    5 |   PyObject* list = PyList_New(2);
> │
>     |      |                    ~~~~~~~~~~~~~
> │
>     |      |                    |
> │
>     |      |                    (3) when ‘PyList_New’ fails
> │
>     |......
> │
>     |   21 |   return list;
> │
>     |      |          ~~~~
> │
>     |      |          |
> │
>     |      |          (4) ‘item’ leaks here; was allocated at (1)
> │
>
> 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>
> ---
>  gcc/analyzer/call-details.h                   |   4 +
>  gcc/analyzer/region-model.cc                  |  17 +-
>  gcc/analyzer/region-model.h                   |  14 +-
>  gcc/analyzer/sm-malloc.cc                     |  42 +
>  .../gcc.dg/plugin/analyzer_cpython_plugin.c   | 722 ++++++++++++++++++
>  .../gcc.dg/plugin/cpython-plugin-test-2.c     |  78 ++
>  gcc/testsuite/gcc.dg/plugin/plugin.exp        |   3 +-
>  gcc/testsuite/lib/target-supports.exp         |  25 +
>  8 files changed, 899 insertions(+), 6 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/plugin/cpython-plugin-test-2.c
>
> diff --git a/gcc/analyzer/call-details.h b/gcc/analyzer/call-details.h
> index 24be2247e63..bf2601151ea 100644
> --- a/gcc/analyzer/call-details.h
> +++ b/gcc/analyzer/call-details.h
> @@ -49,6 +49,10 @@ public:
>      return POINTER_TYPE_P (get_arg_type (idx));
>    }
>    bool arg_is_size_p (unsigned idx) const;
> +  bool arg_is_integral_p (unsigned idx) const
> +  {
> +    return INTEGRAL_TYPE_P (get_arg_type (idx));
> +  }
>
>    const gcall *get_call_stmt () const { return m_call; }
>    location_t get_location () const;
> diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
> index 094b7af3dbc..aa9fe008b9d 100644
> --- a/gcc/analyzer/region-model.cc
> +++ b/gcc/analyzer/region-model.cc
> @@ -4991,11 +4991,16 @@ region_model::check_dynamic_size_for_floats (const svalue *size_in_bytes,
>     Use CTXT to complain about tainted sizes.
>
>     Reuse an existing heap_allocated_region if it's not being referenced by
> -   this region_model; otherwise create a new one.  */
> +   this region_model; otherwise create a new one.
> +
> +   Optionally (update_state_machine) transitions the pointer pointing to the
> +   heap_allocated_region from start to assumed non-null.  */
>
>  const region *
>  region_model::get_or_create_region_for_heap_alloc (const svalue *size_in_bytes,
> -                                                  region_model_context *ctxt)
> +       region_model_context *ctxt,
> +       bool update_state_machine,
> +       const call_details *cd)
>  {
>    /* Determine which regions are referenced in this region_model, so that
>       we can reuse an existing heap_allocated_region if it's not in use on
> @@ -5017,6 +5022,14 @@ region_model::get_or_create_region_for_heap_alloc (const svalue *size_in_bytes,
>    if (size_in_bytes)
>      if (compat_types_p (size_in_bytes->get_type (), size_type_node))
>        set_dynamic_extents (reg, size_in_bytes, ctxt);
> +
> +       if (update_state_machine && cd)
> +               {
> +                       const svalue *ptr_sval
> +                       = m_mgr->get_ptr_svalue (cd->get_lhs_type (), reg);
> +      transition_ptr_sval_non_null (ctxt, ptr_sval);
> +               }
> +
>    return reg;
>  }
>
> diff --git a/gcc/analyzer/region-model.h b/gcc/analyzer/region-model.h
> index 0cf38714c96..a8acad8b7b2 100644
> --- a/gcc/analyzer/region-model.h
> +++ b/gcc/analyzer/region-model.h
> @@ -387,9 +387,12 @@ class region_model
>                        region_model_context *ctxt,
>                        rejected_constraint **out);
>
> -  const region *
> -  get_or_create_region_for_heap_alloc (const svalue *size_in_bytes,
> -                                      region_model_context *ctxt);
> +       const region *
> +       get_or_create_region_for_heap_alloc (const svalue *size_in_bytes,
> +                               region_model_context *ctxt,
> +                               bool update_state_machine = false,
> +                               const call_details *cd = nullptr);
> +
>    const region *create_region_for_alloca (const svalue *size_in_bytes,
>                                           region_model_context *ctxt);
>    void get_referenced_base_regions (auto_bitmap &out_ids) const;
> @@ -476,6 +479,11 @@ class region_model
>                              const svalue *old_ptr_sval,
>                              const svalue *new_ptr_sval);
>
> +  /* Implemented in sm-malloc.cc.  */
> +  void
> +  transition_ptr_sval_non_null (region_model_context *ctxt,
> +      const svalue *new_ptr_sval);
> +
>    /* Implemented in sm-taint.cc.  */
>    void mark_as_tainted (const svalue *sval,
>                         region_model_context *ctxt);
> diff --git a/gcc/analyzer/sm-malloc.cc b/gcc/analyzer/sm-malloc.cc
> index a8c63eb1ce8..ec763254b29 100644
> --- a/gcc/analyzer/sm-malloc.cc
> +++ b/gcc/analyzer/sm-malloc.cc
> @@ -434,6 +434,11 @@ public:
>                              const svalue *new_ptr_sval,
>                              const extrinsic_state &ext_state) const;
>
> +  void transition_ptr_sval_non_null (region_model *model,
> +      sm_state_map *smap,
> +      const svalue *new_ptr_sval,
> +      const extrinsic_state &ext_state) const;
> +
>    standard_deallocator_set m_free;
>    standard_deallocator_set m_scalar_delete;
>    standard_deallocator_set m_vector_delete;
> @@ -2504,6 +2509,17 @@ on_realloc_with_move (region_model *model,
>                    NULL, ext_state);
>  }
>
> +/*  Hook for get_or_create_region_for_heap_alloc for the case when we want
> +   ptr_sval to mark a newly created region as assumed non null on malloc SM.  */
> +void
> +malloc_state_machine::transition_ptr_sval_non_null (region_model *model,
> +    sm_state_map *smap,
> +    const svalue *new_ptr_sval,
> +    const extrinsic_state &ext_state) const
> +{
> +  smap->set_state (model, new_ptr_sval, m_free.m_nonnull, NULL, ext_state);
> +}
> +
>  } // anonymous namespace
>
>  /* Internal interface to this file. */
> @@ -2548,6 +2564,32 @@ region_model::on_realloc_with_move (const call_details &cd,
>                                   *ext_state);
>  }
>
> +/* Moves ptr_sval from start to assumed non-null, for use by
> +   region_model::get_or_create_region_for_heap_alloc.  */
> +void
> +region_model::transition_ptr_sval_non_null (region_model_context *ctxt,
> +const svalue *ptr_sval)
> +{
> +  if (!ctxt)
> +    return;
> +  const extrinsic_state *ext_state = ctxt->get_ext_state ();
> +  if (!ext_state)
> +    return;
> +
> +  sm_state_map *smap;
> +  const state_machine *sm;
> +  unsigned sm_idx;
> +  if (!ctxt->get_malloc_map (&smap, &sm, &sm_idx))
> +    return;
> +
> +  gcc_assert (smap);
> +  gcc_assert (sm);
> +
> +  const malloc_state_machine &malloc_sm = (const malloc_state_machine &)*sm;
> +
> +  malloc_sm.transition_ptr_sval_non_null (this, smap, ptr_sval, *ext_state);
> +}
> +
>  } // namespace ana
>
>  #endif /* #if ENABLE_ANALYZER */
> diff --git a/gcc/testsuite/gcc.dg/plugin/analyzer_cpython_plugin.c b/gcc/testsuite/gcc.dg/plugin/analyzer_cpython_plugin.c
> index 9ecc42d4465..7cd72e8a886 100644
> --- a/gcc/testsuite/gcc.dg/plugin/analyzer_cpython_plugin.c
> +++ b/gcc/testsuite/gcc.dg/plugin/analyzer_cpython_plugin.c
> @@ -55,6 +55,8 @@ static GTY (()) hash_map<tree, tree> *analyzer_stashed_globals;
>  namespace ana
>  {
>  static tree pyobj_record = NULL_TREE;
> +static tree pyobj_ptr_tree = NULL_TREE;
> +static tree pyobj_ptr_ptr = NULL_TREE;
>  static tree varobj_record = NULL_TREE;
>  static tree pylistobj_record = NULL_TREE;
>  static tree pylongobj_record = NULL_TREE;
> @@ -76,6 +78,714 @@ get_field_by_name (tree type, const char *name)
>    return NULL_TREE;
>  }
>
> +static const svalue *
> +get_sizeof_pyobjptr (region_model_manager *mgr)
> +{
> +  tree size_tree = TYPE_SIZE_UNIT (pyobj_ptr_tree);
> +  const svalue *sizeof_sval = mgr->get_or_create_constant_svalue (size_tree);
> +  return sizeof_sval;
> +}
> +
> +/* Update MODEL to set OB_BASE_REGION's ob_refcnt to 1.  */
> +static void
> +init_ob_refcnt_field (region_model_manager *mgr, region_model *model,
> +                      const region *ob_base_region, tree pyobj_record,
> +                      const call_details &cd)
> +{
> +  tree ob_refcnt_tree = get_field_by_name (pyobj_record, "ob_refcnt");
> +  const region *ob_refcnt_region
> +      = mgr->get_field_region (ob_base_region, ob_refcnt_tree);
> +  const svalue *refcnt_one_sval
> +      = mgr->get_or_create_int_cst (size_type_node, 1);
> +  model->set_value (ob_refcnt_region, refcnt_one_sval, cd.get_ctxt ());
> +}
> +
> +/* Update MODEL to set OB_BASE_REGION's ob_type to point to
> +   PYTYPE_VAR_DECL_PTR.  */
> +static void
> +set_ob_type_field (region_model_manager *mgr, region_model *model,
> +                   const region *ob_base_region, tree pyobj_record,
> +                   tree pytype_var_decl_ptr, const call_details &cd)
> +{
> +  const region *pylist_type_region
> +      = mgr->get_region_for_global (pytype_var_decl_ptr);
> +  tree pytype_var_decl_ptr_type
> +      = build_pointer_type (TREE_TYPE (pytype_var_decl_ptr));
> +  const svalue *pylist_type_ptr_sval
> +      = mgr->get_ptr_svalue (pytype_var_decl_ptr_type, pylist_type_region);
> +  tree ob_type_field = get_field_by_name (pyobj_record, "ob_type");
> +  const region *ob_type_region
> +      = mgr->get_field_region (ob_base_region, ob_type_field);
> +  model->set_value (ob_type_region, pylist_type_ptr_sval, cd.get_ctxt ());
> +}
> +
> +/* Retrieve the "ob_base" field's region from OBJECT_RECORD within
> +   NEW_OBJECT_REGION and set its value in the MODEL to PYOBJ_SVALUE. */
> +static const region *
> +get_ob_base_region (region_model_manager *mgr, region_model *model,
> +                   const region *new_object_region, tree object_record,
> +                   const svalue *pyobj_svalue, const call_details &cd)
> +{
> +  tree ob_base_tree = get_field_by_name (object_record, "ob_base");
> +  const region *ob_base_region
> +      = mgr->get_field_region (new_object_region, ob_base_tree);
> +  model->set_value (ob_base_region, pyobj_svalue, cd.get_ctxt ());
> +  return ob_base_region;
> +}
> +
> +/* Initialize and retrieve a region within the MODEL for a PyObject
> +   and set its value to OBJECT_SVALUE. */
> +static const region *
> +init_pyobject_region (region_model_manager *mgr, region_model *model,
> +                      const svalue *object_svalue, const call_details &cd)
> +{
> +  const region *pyobject_region = model->get_or_create_region_for_heap_alloc (
> +      NULL, cd.get_ctxt (), true, &cd);
> +  model->set_value (pyobject_region, object_svalue, cd.get_ctxt ());
> +  return pyobject_region;
> +}
> +
> +/* Increment the value of FIELD_REGION in the MODEL by 1. Optionally
> +   capture the old and new svalues if OLD_SVAL and NEW_SVAL pointers are
> +   provided. */
> +static void
> +inc_field_val (region_model_manager *mgr, region_model *model,
> +               const region *field_region, const tree type_node,
> +               const call_details &cd, const svalue **old_sval = nullptr,
> +               const svalue **new_sval = nullptr)
> +{
> +  const svalue *tmp_old_sval
> +      = model->get_store_value (field_region, cd.get_ctxt ());
> +  const svalue *one_sval = mgr->get_or_create_int_cst (type_node, 1);
> +  const svalue *tmp_new_sval = mgr->get_or_create_binop (
> +      type_node, PLUS_EXPR, tmp_old_sval, one_sval);
> +
> +  model->set_value (field_region, tmp_new_sval, cd.get_ctxt ());
> +
> +  if (old_sval)
> +    *old_sval = tmp_old_sval;
> +
> +  if (new_sval)
> +    *new_sval = tmp_new_sval;
> +}
> +
> +class pyobj_init_fail : public failed_call_info
> +{
> +public:
> +  pyobj_init_fail (const call_details &cd) : failed_call_info (cd) {}
> +
> +  bool
> +  update_model (region_model *model, const exploded_edge *,
> +                region_model_context *ctxt) const final override
> +  {
> +    /* Return NULL; everything else is unchanged. */
> +    const call_details cd (get_call_details (model, ctxt));
> +    region_model_manager *mgr = cd.get_manager ();
> +    if (cd.get_lhs_type ())
> +      {
> +        const svalue *zero
> +            = mgr->get_or_create_int_cst (cd.get_lhs_type (), 0);
> +        model->set_value (cd.get_lhs_region (), zero, cd.get_ctxt ());
> +      }
> +    return true;
> +  }
> +};
> +
> +/* 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. */
> +class kf_PyList_Append : public known_function
> +{
> +public:
> +  bool
> +  matches_call_types_p (const call_details &cd) const final override
> +  {
> +    return (cd.num_args () == 2 && cd.arg_is_pointer_p (0)
> +            && cd.arg_is_pointer_p (1));
> +  }
> +  void impl_call_pre (const call_details &cd) const final override;
> +  void impl_call_post (const call_details &cd) const final override;
> +};
> +
> +void
> +kf_PyList_Append::impl_call_pre (const call_details &cd) const
> +{
> +  region_model_manager *mgr = cd.get_manager ();
> +  region_model *model = cd.get_model ();
> +
> +  const svalue *pylist_sval = cd.get_arg_svalue (0);
> +  const region *pylist_reg
> +      = model->deref_rvalue (pylist_sval, cd.get_arg_tree (0), cd.get_ctxt ());
> +
> +  const svalue *newitem_sval = cd.get_arg_svalue (1);
> +  const region *newitem_reg
> +      = model->deref_rvalue (pylist_sval, cd.get_arg_tree (0), cd.get_ctxt ());
> +
> +  // Skip checks if unknown etc
> +  if (pylist_sval->get_kind () != SK_REGION
> +      && pylist_sval->get_kind () != SK_CONSTANT)
> +    return;
> +
> +  // PyList_Check
> +  tree ob_type_field = get_field_by_name (pyobj_record, "ob_type");
> +  const region *ob_type_region
> +      = mgr->get_field_region (pylist_reg, ob_type_field);
> +  const svalue *stored_sval
> +      = model->get_store_value (ob_type_region, cd.get_ctxt ());
> +  const region *pylist_type_region
> +      = mgr->get_region_for_global (pylisttype_vardecl);
> +  tree pylisttype_vardecl_ptr
> +      = build_pointer_type (TREE_TYPE (pylisttype_vardecl));
> +  const svalue *pylist_type_ptr
> +      = mgr->get_ptr_svalue (pylisttype_vardecl_ptr, pylist_type_region);
> +
> +  if (stored_sval != pylist_type_ptr)
> +    {
> +      // TODO: emit diagnostic -Wanalyzer-type-error
> +      cd.get_ctxt ()->terminate_path ();
> +      return;
> +    }
> +
> +  // Check that new_item is not null.
> +  {
> +    const svalue *null_ptr
> +        = mgr->get_or_create_int_cst (newitem_sval->get_type (), 0);
> +    if (!model->add_constraint (newitem_sval, NE_EXPR, null_ptr,
> +                                cd.get_ctxt ()))
> +      {
> +        // TODO: emit diagnostic here
> +        cd.get_ctxt ()->terminate_path ();
> +        return;
> +      }
> +  }
> +}
> +
> +void
> +kf_PyList_Append::impl_call_post (const call_details &cd) const
> +{
> +  /* Three custom subclasses of custom_edge_info, for handling the various
> +     outcomes of "realloc".  */
> +
> +  /* Concrete custom_edge_info: a realloc call that fails, returning NULL.
> +   */
> +  class realloc_failure : public failed_call_info
> +  {
> +  public:
> +    realloc_failure (const call_details &cd) : failed_call_info (cd) {}
> +
> +    bool
> +    update_model (region_model *model, const exploded_edge *,
> +                  region_model_context *ctxt) const final override
> +    {
> +      const call_details cd (get_call_details (model, ctxt));
> +      region_model_manager *mgr = cd.get_manager ();
> +
> +      const svalue *pylist_sval = cd.get_arg_svalue (0);
> +      const region *pylist_reg = model->deref_rvalue (
> +          pylist_sval, cd.get_arg_tree (0), cd.get_ctxt ());
> +
> +      /* Identify ob_item field and set it to NULL. */
> +      tree ob_item_field = get_field_by_name (pylistobj_record, "ob_item");
> +      const region *ob_item_reg
> +          = mgr->get_field_region (pylist_reg, ob_item_field);
> +      const svalue *old_ptr_sval
> +          = model->get_store_value (ob_item_reg, cd.get_ctxt ());
> +
> +      if (const region_svalue *old_reg
> +          = old_ptr_sval->dyn_cast_region_svalue ())
> +        {
> +          const region *freed_reg = old_reg->get_pointee ();
> +          model->unbind_region_and_descendents (freed_reg, POISON_KIND_FREED);
> +          model->unset_dynamic_extents (freed_reg);
> +        }
> +
> +      const svalue *null_sval = mgr->get_or_create_null_ptr (pyobj_ptr_ptr);
> +      model->set_value (ob_item_reg, null_sval, cd.get_ctxt ());
> +
> +      if (cd.get_lhs_type ())
> +        {
> +          const svalue *neg_one
> +              = mgr->get_or_create_int_cst (cd.get_lhs_type (), -1);
> +          cd.maybe_set_lhs(neg_one);
> +        }
> +      return true;
> +    }
> +  };
> +
> +  class realloc_success_no_move : public call_info
> +  {
> +  public:
> +    realloc_success_no_move (const call_details &cd) : call_info (cd) {}
> +
> +    label_text
> +    get_desc (bool can_colorize) const final override
> +    {
> +      return make_label_text (
> +          can_colorize, "when %qE succeeds, without moving underlying buffer",
> +          get_fndecl ());
> +    }
> +
> +    bool
> +    update_model (region_model *model, const exploded_edge *,
> +                  region_model_context *ctxt) const final override
> +    {
> +      const call_details cd (get_call_details (model, ctxt));
> +      region_model_manager *mgr = cd.get_manager ();
> +
> +      const svalue *pylist_sval = cd.get_arg_svalue (0);
> +      const region *pylist_reg = model->deref_rvalue (
> +          pylist_sval, cd.get_arg_tree (0), cd.get_ctxt ());
> +
> +      const svalue *newitem_sval = cd.get_arg_svalue (1);
> +      const region *newitem_reg = model->deref_rvalue (
> +          newitem_sval, cd.get_arg_tree (1), cd.get_ctxt ());
> +
> +      tree ob_size_field = get_field_by_name (varobj_record, "ob_size");
> +      const region *ob_size_region
> +          = mgr->get_field_region (pylist_reg, ob_size_field);
> +      const svalue *ob_size_sval = nullptr;
> +      const svalue *new_size_sval = nullptr;
> +      inc_field_val (mgr, model, ob_size_region, integer_type_node, cd,
> +                     &ob_size_sval, &new_size_sval);
> +
> +      const svalue *sizeof_sval = mgr->get_or_create_cast (
> +          ob_size_sval->get_type (), get_sizeof_pyobjptr (mgr));
> +      const svalue *num_allocated_bytes = mgr->get_or_create_binop (
> +          size_type_node, MULT_EXPR, sizeof_sval, new_size_sval);
> +
> +      tree ob_item_field = get_field_by_name (pylistobj_record, "ob_item");
> +      const region *ob_item_region
> +          = mgr->get_field_region (pylist_reg, ob_item_field);
> +      const svalue *ob_item_ptr_sval
> +          = model->get_store_value (ob_item_region, cd.get_ctxt ());
> +
> +      /* We can only grow in place with a non-NULL pointer and no unknown
> +       */
> +      {
> +        const svalue *null_ptr = mgr->get_or_create_null_ptr (pyobj_ptr_ptr);
> +        if (!model->add_constraint (ob_item_ptr_sval, NE_EXPR, null_ptr,
> +                                    cd.get_ctxt ()))
> +          {
> +            return false;
> +          }
> +      }
> +
> +      const unmergeable_svalue *underlying_svalue
> +          = ob_item_ptr_sval->dyn_cast_unmergeable_svalue ();
> +      const svalue *target_svalue = nullptr;
> +      const region_svalue *target_region_svalue = nullptr;
> +
> +      if (underlying_svalue)
> +        {
> +          target_svalue = underlying_svalue->get_arg ();
> +          if (target_svalue->get_kind () != SK_REGION)
> +            {
> +              return false;
> +            }
> +        }
> +      else
> +        {
> +          if (ob_item_ptr_sval->get_kind () != SK_REGION)
> +            {
> +              return false;
> +            }
> +          target_svalue = ob_item_ptr_sval;
> +        }
> +
> +      target_region_svalue = target_svalue->dyn_cast_region_svalue ();
> +      const region *curr_reg = target_region_svalue->get_pointee ();
> +
> +      if (compat_types_p (num_allocated_bytes->get_type (), size_type_node))
> +        model->set_dynamic_extents (curr_reg, num_allocated_bytes, ctxt);
> +
> +      model->set_value (ob_size_region, new_size_sval, ctxt);
> +
> +      const svalue *offset_sval = mgr->get_or_create_binop (
> +          size_type_node, MULT_EXPR, sizeof_sval, ob_size_sval);
> +      const region *element_region
> +          = mgr->get_offset_region (curr_reg, pyobj_ptr_ptr, offset_sval);
> +      model->set_value (element_region, newitem_sval, cd.get_ctxt ());
> +
> +      // Increment ob_refcnt of appended item.
> +      tree ob_refcnt_tree = get_field_by_name (pyobj_record, "ob_refcnt");
> +      const region *ob_refcnt_region
> +          = mgr->get_field_region (newitem_reg, ob_refcnt_tree);
> +      inc_field_val (mgr, model, ob_refcnt_region, size_type_node, cd);
> +
> +      if (cd.get_lhs_type ())
> +        {
> +          const svalue *zero
> +              = mgr->get_or_create_int_cst (cd.get_lhs_type (), 0);
> +          cd.maybe_set_lhs(zero);
> +        }
> +      return true;
> +    }
> +  };
> +
> +  class realloc_success_move : public call_info
> +  {
> +  public:
> +    realloc_success_move (const call_details &cd) : call_info (cd) {}
> +
> +    label_text
> +    get_desc (bool can_colorize) const final override
> +    {
> +      return make_label_text (can_colorize, "when %qE succeeds, moving buffer",
> +                              get_fndecl ());
> +    }
> +
> +    bool
> +    update_model (region_model *model, const exploded_edge *,
> +                  region_model_context *ctxt) const final override
> +    {
> +      const call_details cd (get_call_details (model, ctxt));
> +      region_model_manager *mgr = cd.get_manager ();
> +      const svalue *pylist_sval = cd.get_arg_svalue (0);
> +      const region *pylist_reg = model->deref_rvalue (
> +          pylist_sval, cd.get_arg_tree (0), cd.get_ctxt ());
> +
> +      const svalue *newitem_sval = cd.get_arg_svalue (1);
> +      const region *newitem_reg = model->deref_rvalue (
> +          newitem_sval, cd.get_arg_tree (1), cd.get_ctxt ());
> +
> +      tree ob_size_field = get_field_by_name (varobj_record, "ob_size");
> +      const region *ob_size_region
> +          = mgr->get_field_region (pylist_reg, ob_size_field);
> +      const svalue *old_ob_size_sval = nullptr;
> +      const svalue *new_ob_size_sval = nullptr;
> +      inc_field_val (mgr, model, ob_size_region, integer_type_node, cd,
> +                     &old_ob_size_sval, &new_ob_size_sval);
> +
> +      const svalue *sizeof_sval = mgr->get_or_create_cast (
> +          old_ob_size_sval->get_type (), get_sizeof_pyobjptr (mgr));
> +      const svalue *new_size_sval = mgr->get_or_create_binop (
> +          size_type_node, MULT_EXPR, sizeof_sval, new_ob_size_sval);
> +
> +      tree ob_item_field = get_field_by_name (pylistobj_record, "ob_item");
> +      const region *ob_item_reg
> +          = mgr->get_field_region (pylist_reg, ob_item_field);
> +      const svalue *old_ptr_sval
> +          = model->get_store_value (ob_item_reg, cd.get_ctxt ());
> +
> +      /* Create the new region.  */
> +      const region *new_reg = model->get_or_create_region_for_heap_alloc (
> +          new_size_sval, cd.get_ctxt ());
> +      const svalue *new_ptr_sval
> +          = mgr->get_ptr_svalue (pyobj_ptr_ptr, new_reg);
> +      if (!model->add_constraint (new_ptr_sval, NE_EXPR, old_ptr_sval,
> +                                  cd.get_ctxt ()))
> +        return false;
> +
> +      if (const region_svalue *old_reg
> +          = old_ptr_sval->dyn_cast_region_svalue ())
> +        {
> +          const region *freed_reg = old_reg->get_pointee ();
> +          const svalue *old_size_sval = model->get_dynamic_extents (freed_reg);
> +          if (old_size_sval)
> +            {
> +              const svalue *copied_size_sval
> +                  = get_copied_size (model, old_size_sval, new_size_sval);
> +              const region *copied_old_reg = mgr->get_sized_region (
> +                  freed_reg, pyobj_ptr_ptr, copied_size_sval);
> +              const svalue *buffer_content_sval
> +                  = model->get_store_value (copied_old_reg, cd.get_ctxt ());
> +              const region *copied_new_reg = mgr->get_sized_region (
> +                  new_reg, pyobj_ptr_ptr, copied_size_sval);
> +              model->set_value (copied_new_reg, buffer_content_sval,
> +                                cd.get_ctxt ());
> +            }
> +          else
> +            {
> +              model->mark_region_as_unknown (freed_reg, cd.get_uncertainty ());
> +            }
> +
> +          model->unbind_region_and_descendents (freed_reg, POISON_KIND_FREED);
> +          model->unset_dynamic_extents (freed_reg);
> +        }
> +
> +      const svalue *null_ptr = mgr->get_or_create_null_ptr (pyobj_ptr_ptr);
> +      if (!model->add_constraint (new_ptr_sval, NE_EXPR, null_ptr,
> +                                  cd.get_ctxt ()))
> +        return false;
> +
> +      model->set_value (ob_size_region, new_ob_size_sval, ctxt);
> +      model->set_value (ob_item_reg, new_ptr_sval, cd.get_ctxt ());
> +
> +      const svalue *offset_sval = mgr->get_or_create_binop (
> +          size_type_node, MULT_EXPR, sizeof_sval, old_ob_size_sval);
> +      const region *element_region
> +          = mgr->get_offset_region (new_reg, pyobj_ptr_ptr, offset_sval);
> +      model->set_value (element_region, newitem_sval, cd.get_ctxt ());
> +
> +      // Increment ob_refcnt of appended item.
> +      tree ob_refcnt_tree = get_field_by_name (pyobj_record, "ob_refcnt");
> +      const region *ob_refcnt_region
> +          = mgr->get_field_region (newitem_reg, ob_refcnt_tree);
> +      inc_field_val (mgr, model, ob_refcnt_region, size_type_node, cd);
> +
> +      if (cd.get_lhs_type ())
> +        {
> +          const svalue *zero
> +              = mgr->get_or_create_int_cst (cd.get_lhs_type (), 0);
> +          cd.maybe_set_lhs(zero);
> +        }
> +      return true;
> +    }
> +
> +  private:
> +    /* Return the lesser of OLD_SIZE_SVAL and NEW_SIZE_SVAL.
> +       If unknown, OLD_SIZE_SVAL is returned.  */
> +    const svalue *
> +    get_copied_size (region_model *model, const svalue *old_size_sval,
> +                     const svalue *new_size_sval) const
> +    {
> +      tristate res
> +          = model->eval_condition (old_size_sval, GT_EXPR, new_size_sval);
> +      switch (res.get_value ())
> +        {
> +        case tristate::TS_TRUE:
> +          return new_size_sval;
> +        case tristate::TS_FALSE:
> +        case tristate::TS_UNKNOWN:
> +          return old_size_sval;
> +        default:
> +          gcc_unreachable ();
> +        }
> +    }
> +  };
> +
> +  /* Body of kf_PyList_Append::impl_call_post.  */
> +  if (cd.get_ctxt ())
> +    {
> +      cd.get_ctxt ()->bifurcate (make_unique<realloc_failure> (cd));
> +      cd.get_ctxt ()->bifurcate (make_unique<realloc_success_no_move> (cd));
> +      cd.get_ctxt ()->bifurcate (make_unique<realloc_success_move> (cd));
> +      cd.get_ctxt ()->terminate_path ();
> +    }
> +}
> +
> +class kf_PyList_New : public known_function
> +{
> +public:
> +  bool
> +  matches_call_types_p (const call_details &cd) const final override
> +  {
> +    return (cd.num_args () == 1 && cd.arg_is_integral_p (0));
> +  }
> +  void impl_call_post (const call_details &cd) const final override;
> +};
> +
> +void
> +kf_PyList_New::impl_call_post (const call_details &cd) const
> +{
> +  class success : public call_info
> +  {
> +  public:
> +    success (const call_details &cd) : call_info (cd) {}
> +
> +    label_text
> +    get_desc (bool can_colorize) const final override
> +    {
> +      return make_label_text (can_colorize, "when %qE succeeds",
> +                              get_fndecl ());
> +    }
> +
> +    bool
> +    update_model (region_model *model, const exploded_edge *,
> +                  region_model_context *ctxt) const final override
> +    {
> +      const call_details cd (get_call_details (model, ctxt));
> +      region_model_manager *mgr = cd.get_manager ();
> +
> +      const svalue *pyobj_svalue
> +          = mgr->get_or_create_unknown_svalue (pyobj_record);
> +      const svalue *varobj_svalue
> +          = mgr->get_or_create_unknown_svalue (varobj_record);
> +      const svalue *pylist_svalue
> +          = mgr->get_or_create_unknown_svalue (pylistobj_record);
> +
> +      const svalue *size_sval = cd.get_arg_svalue (0);
> +
> +      const region *pylist_region
> +          = init_pyobject_region (mgr, model, pylist_svalue, cd);
> +
> +      /*
> +      typedef struct
> +      {
> +        PyObject_VAR_HEAD
> +        PyObject **ob_item;
> +        Py_ssize_t allocated;
> +      } PyListObject;
> +      */
> +      tree varobj_field = get_field_by_name (pylistobj_record, "ob_base");
> +      const region *varobj_region
> +          = mgr->get_field_region (pylist_region, varobj_field);
> +      model->set_value (varobj_region, varobj_svalue, cd.get_ctxt ());
> +
> +      tree ob_item_field = get_field_by_name (pylistobj_record, "ob_item");
> +      const region *ob_item_region
> +          = mgr->get_field_region (pylist_region, ob_item_field);
> +
> +      const svalue *zero_sval = mgr->get_or_create_int_cst (size_type_node, 0);
> +      const svalue *casted_size_sval
> +          = mgr->get_or_create_cast (size_type_node, size_sval);
> +      const svalue *size_cond_sval = mgr->get_or_create_binop (
> +          size_type_node, LE_EXPR, casted_size_sval, zero_sval);
> +
> +      // if size <= 0, ob_item = NULL
> +
> +      if (tree_int_cst_equal (size_cond_sval->maybe_get_constant (),
> +                              integer_one_node))
> +        {
> +          const svalue *null_sval
> +              = mgr->get_or_create_null_ptr (pyobj_ptr_ptr);
> +          model->set_value (ob_item_region, null_sval, cd.get_ctxt ());
> +        }
> +      else // calloc
> +        {
> +          const svalue *sizeof_sval = mgr->get_or_create_cast (
> +              size_sval->get_type (), get_sizeof_pyobjptr (mgr));
> +          const svalue *prod_sval = mgr->get_or_create_binop (
> +              size_type_node, MULT_EXPR, sizeof_sval, size_sval);
> +          const region *ob_item_sized_region
> +              = model->get_or_create_region_for_heap_alloc (prod_sval,
> +                                                            cd.get_ctxt ());
> +          model->zero_fill_region (ob_item_sized_region);
> +          const svalue *ob_item_ptr_sval
> +              = mgr->get_ptr_svalue (pyobj_ptr_ptr, ob_item_sized_region);
> +          const svalue *ob_item_unmergeable
> +              = mgr->get_or_create_unmergeable (ob_item_ptr_sval);
> +          model->set_value (ob_item_region, ob_item_unmergeable,
> +                            cd.get_ctxt ());
> +        }
> +
> +      /*
> +      typedef struct {
> +      PyObject ob_base;
> +      Py_ssize_t ob_size; // Number of items in variable part
> +      } PyVarObject;
> +      */
> +      const region *ob_base_region = get_ob_base_region (
> +          mgr, model, varobj_region, varobj_record, pyobj_svalue, cd);
> +
> +      tree ob_size_tree = get_field_by_name (varobj_record, "ob_size");
> +      const region *ob_size_region
> +          = mgr->get_field_region (varobj_region, ob_size_tree);
> +      model->set_value (ob_size_region, size_sval, cd.get_ctxt ());
> +
> +      /*
> +      typedef struct _object {
> +          _PyObject_HEAD_EXTRA
> +          Py_ssize_t ob_refcnt;
> +          PyTypeObject *ob_type;
> +      } PyObject;
> +      */
> +
> +      // Initialize ob_refcnt field to 1.
> +      init_ob_refcnt_field(mgr, model, ob_base_region, pyobj_record, cd);
> +
> +      // Get pointer svalue for PyList_Type then assign it to ob_type field.
> +      set_ob_type_field(mgr, model, ob_base_region, pyobj_record, pylisttype_vardecl, cd);
> +
> +      if (cd.get_lhs_type ())
> +        {
> +          const svalue *ptr_sval
> +              = mgr->get_ptr_svalue (cd.get_lhs_type (), pylist_region);
> +          cd.maybe_set_lhs (ptr_sval);
> +        }
> +      return true;
> +    }
> +  };
> +
> +  if (cd.get_ctxt ())
> +    {
> +      cd.get_ctxt ()->bifurcate (make_unique<pyobj_init_fail> (cd));
> +      cd.get_ctxt ()->bifurcate (make_unique<success> (cd));
> +      cd.get_ctxt ()->terminate_path ();
> +    }
> +}
> +
> +class kf_PyLong_FromLong : public known_function
> +{
> +public:
> +  bool
> +  matches_call_types_p (const call_details &cd) const final override
> +  {
> +    return (cd.num_args () == 1 && cd.arg_is_integral_p (0));
> +  }
> +  void impl_call_post (const call_details &cd) const final override;
> +};
> +
> +void
> +kf_PyLong_FromLong::impl_call_post (const call_details &cd) const
> +{
> +  class success : public call_info
> +  {
> +  public:
> +    success (const call_details &cd) : call_info (cd) {}
> +
> +    label_text
> +    get_desc (bool can_colorize) const final override
> +    {
> +      return make_label_text (can_colorize, "when %qE succeeds",
> +                              get_fndecl ());
> +    }
> +
> +    bool
> +    update_model (region_model *model, const exploded_edge *,
> +                  region_model_context *ctxt) const final override
> +    {
> +      const call_details cd (get_call_details (model, ctxt));
> +      region_model_manager *mgr = cd.get_manager ();
> +
> +      const svalue *pyobj_svalue
> +          = mgr->get_or_create_unknown_svalue (pyobj_record);
> +      const svalue *pylongobj_sval
> +          = mgr->get_or_create_unknown_svalue (pylongobj_record);
> +
> +      const region *pylong_region
> +          = init_pyobject_region (mgr, model, pylongobj_sval, cd);
> +
> +      // Create a region for the base PyObject within the PyLongObject.
> +      const region *ob_base_region = get_ob_base_region (
> +          mgr, model, pylong_region, pylongobj_record, pyobj_svalue, cd);
> +
> +      // Initialize ob_refcnt field to 1.
> +      init_ob_refcnt_field(mgr, model, ob_base_region, pyobj_record, cd);
> +
> +      // Get pointer svalue for PyLong_Type then assign it to ob_type field.
> +      set_ob_type_field(mgr, model, ob_base_region, pyobj_record, pylongtype_vardecl, cd);
> +
> +      // Set the PyLongObject value.
> +      tree ob_digit_field = get_field_by_name (pylongobj_record, "ob_digit");
> +      const region *ob_digit_region
> +          = mgr->get_field_region (pylong_region, ob_digit_field);
> +      const svalue *ob_digit_sval = cd.get_arg_svalue (0);
> +      model->set_value (ob_digit_region, ob_digit_sval, cd.get_ctxt ());
> +
> +      if (cd.get_lhs_type ())
> +        {
> +          const svalue *ptr_sval
> +              = mgr->get_ptr_svalue (cd.get_lhs_type (), pylong_region);
> +          cd.maybe_set_lhs (ptr_sval);
> +        }
> +      return true;
> +    }
> +  };
> +
> +  if (cd.get_ctxt ())
> +    {
> +      cd.get_ctxt ()->bifurcate (make_unique<pyobj_init_fail> (cd));
> +      cd.get_ctxt ()->bifurcate (make_unique<success> (cd));
> +      cd.get_ctxt ()->terminate_path ();
> +    }
> +}
> +
>  static void
>  maybe_stash_named_type (logger *logger, const translation_unit &tu,
>                          const char *name)
> @@ -179,6 +889,12 @@ init_py_structs ()
>    pylongobj_record = get_stashed_type_by_name ("PyLongObject");
>    pylongtype_vardecl = get_stashed_global_var_by_name ("PyLong_Type");
>    pylisttype_vardecl = get_stashed_global_var_by_name ("PyList_Type");
> +
> +  if (pyobj_record)
> +    {
> +      pyobj_ptr_tree = build_pointer_type (pyobj_record);
> +      pyobj_ptr_ptr = build_pointer_type (pyobj_ptr_tree);
> +    }
>  }
>
>  void
> @@ -205,6 +921,12 @@ cpython_analyzer_init_cb (void *gcc_data, void * /*user_data */)
>        sorry_no_cpython_plugin ();
>        return;
>      }
> +
> +  iface->register_known_function ("PyList_Append",
> +                                  make_unique<kf_PyList_Append> ());
> +  iface->register_known_function ("PyList_New", make_unique<kf_PyList_New> ());
> +  iface->register_known_function ("PyLong_FromLong",
> +                                  make_unique<kf_PyLong_FromLong> ());
>  }
>  } // namespace ana
>
> diff --git a/gcc/testsuite/gcc.dg/plugin/cpython-plugin-test-2.c b/gcc/testsuite/gcc.dg/plugin/cpython-plugin-test-2.c
> new file mode 100644
> index 00000000000..19b5c17428a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/plugin/cpython-plugin-test-2.c
> @@ -0,0 +1,78 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target analyzer } */
> +/* { dg-options "-fanalyzer" } */
> +/* { dg-require-python-h "" } */
> +
> +
> +#define PY_SSIZE_T_CLEAN
> +#include <Python.h>
> +#include "../analyzer/analyzer-decls.h"
> +
> +PyObject *
> +test_PyList_New (Py_ssize_t len)
> +{
> +  PyObject *obj = PyList_New (len);
> +  if (obj)
> +    {
> +     __analyzer_eval (obj->ob_refcnt == 1); /* { dg-warning "TRUE" } */
> +     __analyzer_eval (PyList_CheckExact (obj)); /* { dg-warning "TRUE" } */
> +    }
> +  else
> +    __analyzer_dump_path (); /* { dg-message "path" } */
> +  return obj;
> +}
> +
> +PyObject *
> +test_PyLong_New (long n)
> +{
> +  PyObject *obj = PyLong_FromLong (n);
> +  if (obj)
> +    {
> +     __analyzer_eval (obj->ob_refcnt == 1); /* { dg-warning "TRUE" } */
> +     __analyzer_eval (PyLong_CheckExact (obj)); /* { dg-warning "TRUE" } */
> +    }
> +  else
> +    __analyzer_dump_path (); /* { dg-message "path" } */
> +  return obj;
> +}
> +
> +PyObject *
> +test_PyListAppend (long n)
> +{
> +  PyObject *item = PyLong_FromLong (n);
> +  PyObject *list = PyList_New (0);
> +  PyList_Append(list, item);
> +  return list; /* { dg-warning "leak of 'item'" } */
> +}
> +
> +PyObject *
> +test_PyListAppend_2 (long n)
> +{
> +  PyObject *item = PyLong_FromLong (n);
> +  if (!item)
> +       return NULL;
> +
> +  __analyzer_eval (item->ob_refcnt == 1); /* { dg-warning "TRUE" } */
> +  PyObject *list = PyList_New (n);
> +  if (!list)
> +  {
> +       Py_DECREF(item);
> +       return NULL;
> +  }
> +
> +  __analyzer_eval (list->ob_refcnt == 1); /* { dg-warning "TRUE" } */
> +
> +  if (PyList_Append (list, item) < 0)
> +    __analyzer_eval (item->ob_refcnt == 1); /* { dg-warning "TRUE" } */
> +  else
> +    __analyzer_eval (item->ob_refcnt == 2); /* { dg-warning "TRUE" } */
> +  return list; /* { dg-warning "leak of 'item'" } */
> +}
> +
> +
> +PyObject *
> +test_PyListAppend_3 (PyObject *item, PyObject *list)
> +{
> +  PyList_Append (list, item);
> +  return list;
> +}
> \ No newline at end of file
> diff --git a/gcc/testsuite/gcc.dg/plugin/plugin.exp b/gcc/testsuite/gcc.dg/plugin/plugin.exp
> index 09c45394b1f..e1ed2d2589e 100644
> --- a/gcc/testsuite/gcc.dg/plugin/plugin.exp
> +++ b/gcc/testsuite/gcc.dg/plugin/plugin.exp
> @@ -161,7 +161,8 @@ set plugin_test_list [list \
>           taint-CVE-2011-0521-6.c \
>           taint-antipatterns-1.c } \
>      { analyzer_cpython_plugin.c \
> -         cpython-plugin-test-1.c } \
> +         cpython-plugin-test-1.c \
> +         cpython-plugin-test-2.c } \
>  ]
>
>  foreach plugin_test $plugin_test_list {
> diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
> index 7004711b384..eda53ff3a09 100644
> --- a/gcc/testsuite/lib/target-supports.exp
> +++ b/gcc/testsuite/lib/target-supports.exp
> @@ -12559,3 +12559,28 @@ proc check_effective_target_const_volatile_readonly_section { } {
>      }
>    return 1
>  }
> +
> +# Appends necessary Python flags to extra-tool-flags if Python.h is supported.
> +# Otherwise, modifies dg-do-what.
> +proc dg-require-python-h { args } {
> +    upvar dg-extra-tool-flags extra-tool-flags
> +
> +    verbose "ENTER dg-require-python-h" 2
> +
> +    set result [remote_exec host "python3-config --includes"]
> +    set status [lindex $result 0]
> +    if { $status == 0 } {
> +        set python_flags [lindex $result 1]
> +    } else {
> +       verbose "Python.h not supported" 2
> +       upvar dg-do-what dg-do-what
> +       set dg-do-what [list [lindex ${dg-do-what} 0] "N" "P"]
> +       return
> +    }
> +
> +    verbose "Python flags are: $python_flags" 2
> +
> +    verbose "Before appending, extra-tool-flags: ${extra-tool-flags}" 3
> +    eval lappend extra-tool-flags $python_flags
> +    verbose "After appending, extra-tool-flags: ${extra-tool-flags}" 3
> +}
> --
> 2.30.2
>