[PATCH v2] analyzer: More features for CPython analyzer plugin [PR107646]

[Eric Feng <ef2648@columbia.edu>]

Thank you for your help in getting dg-require-python-h working! I can
confirm that the FAILs are related to differences between the --cflags
affecting the gimple seen by the analyzer. For this reason, I have
changed it to --includes for now. To be sure, I tested on Python 3.8 as
well and it works as expected. I have also addressed the following
comments on the WIP patch as you described.

-- Update Changelog entry to list new functions being simulated.
-- Update region_model::get_or_create_region_for_heap_alloc leading
comment.
-- Change register_alloc to update_state_machine.
-- Change move_ptr_sval_non_null to transition_ptr_sval_non_null.
-- Static helper functions for:
	-- Initializing ob_refcnt field.
	-- Setting ob_type field.
	-- Getting ob_base field.
	-- Initializing heap allocated region for PyObjects.
	-- Incrementing a field by one.
-- Change arg_is_long_p to arg_is_integral_p.
-- Extract common failure scenario for reusability.

The initial WIP patch using 

/* { dg-options "-fanalyzer -I/usr/include/python3.9" }. */

have been bootstrapped and regtested on aarch64-unknown-linux-gnu. Since
we did not change any core logic in the revision and the only changes
within the analyzer core are changing variable names, is it OK for
trunk. In the mean time, the revised patch is currently going through
bootstrap and regtest process.

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
	* 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/region-model.cc                  |  20 +-
 gcc/analyzer/region-model.h                   |  10 +-
 gcc/analyzer/sm-malloc.cc                     |  40 +
 .../gcc.dg/plugin/analyzer_cpython_plugin.c   | 711 ++++++++++++++++++
 .../gcc.dg/plugin/cpython-plugin-test-2.c     |  78 ++
 gcc/testsuite/gcc.dg/plugin/plugin.exp        |   3 +-
 gcc/testsuite/lib/target-supports.exp         |  25 +
 7 files changed, 881 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/plugin/cpython-plugin-test-2.c

diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
index e92b3f7b074..c338f045d92 100644
--- a/gcc/analyzer/region-model.cc
+++ b/gcc/analyzer/region-model.cc
@@ -5127,11 +5127,16 @@ 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
@@ -5153,6 +5158,17 @@ 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 = nullptr;
+			if (cd->get_lhs_type ())
+       ptr_sval = m_mgr->get_ptr_svalue (cd->get_lhs_type (), reg);
+			else
+       ptr_sval = m_mgr->get_ptr_svalue (NULL_TREE, 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..16c80a238bc 100644
--- a/gcc/analyzer/region-model.h
+++ b/gcc/analyzer/region-model.h
@@ -387,9 +387,9 @@ 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 +476,10 @@ 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..bb8d83e4605 100644
--- a/gcc/analyzer/sm-malloc.cc
+++ b/gcc/analyzer/sm-malloc.cc
@@ -434,6 +434,10 @@ 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 +2508,16 @@ 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 +2562,32 @@ 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..42c8aff101e 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 +78,703 @@ 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;
+}
+
+static bool
+arg_is_integral_p(const call_details &cd, unsigned idx)
+{
+  return INTEGRAL_TYPE_P(cd.get_arg_type(idx));
+}
+
+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 ());
+}
+
+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 ());
+}
+
+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;
+}
+
+static const region *
+init_pyobject_region (region_model_manager *mgr, region_model *model,
+                      const svalue *object_svalue, const call_details &cd)
+{
+  /* TODO: switch to actual tp_basic_size */
+  const svalue *tp_basicsize_sval = mgr->get_or_create_unknown_svalue (NULL);
+  const region *pyobject_region = model->get_or_create_region_for_heap_alloc (
+      tp_basicsize_sval, cd.get_ctxt (), true, &cd);
+  model->set_value (pyobject_region, object_svalue, cd.get_ctxt ());
+  return pyobject_region;
+}
+
+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;
+  }
+};
+
+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); // TODO: more checks here
+  }
+  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 && arg_is_integral_p (cd, 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 && arg_is_integral_p (cd, 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 +878,12 @@ 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 +910,12 @@ 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