analyzer: use ultimate alias target at calls (PR 93288)

PR analyzer/93288 reports an ICE in a C++ testcase when calling a
constructor.

The issue is that when building the supergraph, we encounter the
cgraph edge to "__ct_comp ", the DECL_COMPLETE_CONSTRUCTOR_P, and
this node's DECL_STRUCT_FUNCTION has a NULL CFG, which the analyzer
reads through, leading to the ICE.

This patch reworks function and fndecl lookup at calls throughout the
analyzer so that it looks for the ultimate_alias_target of the callee.
In the case above, this means using the "__ct_base " for the ctor,
which has a CFG, fixing the ICE.

Getting this right allows for some simple C++ cases involving ctors to
work, so the patch also adds some test coverage for that.

gcc/analyzer/ChangeLog:
	PR analyzer/93288
	* analysis-plan.cc (analysis_plan::use_summary_p): Look through
	the ultimate_alias_target when getting the called function.
	* engine.cc (exploded_node::on_stmt): Rename second "ctxt" to
	"sm_ctxt".  Use the region_model's get_fndecl_for_call rather than
	gimple_call_fndecl.
	* region-model.cc (region_model::get_fndecl_for_call): Use
	ultimate_alias_target on fndecl.
	* supergraph.cc (get_ultimate_function_for_cgraph_edge): New
	function.
	(supergraph_call_edge): Use it when rejecting edges without
	functions.
	(supergraph::supergraph): Use it to get the function for the
	cgraph_edge when building interprocedural superedges.
	(callgraph_superedge::get_callee_function):  Use it.
	* supergraph.h (supergraph::get_num_snodes): Make param const.
	(supergraph::function_to_num_snodes_t): Make first type param
	const.

gcc/testsuite/ChangeLog:
	PR analyzer/93288
	* g++.dg/analyzer/malloc.C: Add test coverage for a double-free
	called in a constructor.
	* g++.dg/analyzer/pr93288.C: New test.

gcc/analyzer/ChangeLog

@@ -1,3 +1,24 @@
+2020-02-11  David Malcolm  <dmalcolm@redhat.com>
+
+	PR analyzer/93288
+	* analysis-plan.cc (analysis_plan::use_summary_p): Look through
+	the ultimate_alias_target when getting the called function.
+	* engine.cc (exploded_node::on_stmt): Rename second "ctxt" to
+	"sm_ctxt".  Use the region_model's get_fndecl_for_call rather than
+	gimple_call_fndecl.
+	* region-model.cc (region_model::get_fndecl_for_call): Use
+	ultimate_alias_target on fndecl.
+	* supergraph.cc (get_ultimate_function_for_cgraph_edge): New
+	function.
+	(supergraph_call_edge): Use it when rejecting edges without
+	functions.
+	(supergraph::supergraph): Use it to get the function for the
+	cgraph_edge when building interprocedural superedges.
+	(callgraph_superedge::get_callee_function):  Use it.
+	* supergraph.h (supergraph::get_num_snodes): Make param const.
+	(supergraph::function_to_num_snodes_t): Make first type param
+	const.
+
 2020-02-11  David Malcolm  <dmalcolm@redhat.com>
 
 	PR analyzer/93374

gcc/analyzer/analysis-plan.cc

@@ -120,7 +120,11 @@ analysis_plan::use_summary_p (const cgraph_edge *edge) const
 
   /* Require the callee to be sufficiently complex to be worth
      summarizing.  */
-  if ((int)m_sg.get_num_snodes (callee->get_fun ())
+  const function *fun
+    = const_cast <cgraph_node *> (callee)->ultimate_alias_target ()->get_fun ();
+  /* TODO(stage1): can ultimate_alias_target be made const?  */
+
+  if ((int)m_sg.get_num_snodes (fun)
       < param_analyzer_min_snodes_for_call_summary)
     return false;
 

gcc/analyzer/engine.cc

@@ -1044,19 +1044,19 @@ exploded_node::on_stmt (exploded_graph &eg,
       const sm_state_map *old_smap
 	= old_state.m_checker_states[sm_idx];
       sm_state_map *new_smap = state->m_checker_states[sm_idx];
-      impl_sm_context ctxt (eg, sm_idx, sm, this, &old_state, state,
-			    change,
-			    old_smap, new_smap);
+      impl_sm_context sm_ctxt (eg, sm_idx, sm, this, &old_state, state,
+			       change,
+			       old_smap, new_smap);
       /* Allow the state_machine to handle the stmt.  */
-      if (sm.on_stmt (&ctxt, snode, stmt))
+      if (sm.on_stmt (&sm_ctxt, snode, stmt))
 	unknown_side_effects = false;
       else
 	{
 	  /* For those stmts that were not handled by the state machine.  */
 	  if (const gcall *call = dyn_cast <const gcall *> (stmt))
 	    {
-	      tree callee_fndecl = gimple_call_fndecl (call);
-	      // TODO: maybe we can be smarter about handling function pointers?
+	      tree callee_fndecl
+		= state->m_region_model->get_fndecl_for_call (call, &ctxt);
 
 	      if (!fndecl_has_gimple_body_p (callee_fndecl))
 		new_smap->purge_for_unknown_fncall (eg, sm, call, callee_fndecl,

gcc/analyzer/region-model.cc

@@ -6676,7 +6676,10 @@ region_model::get_fndecl_for_call (const gcall *call,
       if (code)
 	{
 	  tree fn_decl = code->get_tree_for_child_region (fn_rid);
-	  return fn_decl;
+	  const cgraph_node *ultimate_node
+	    = cgraph_node::get (fn_decl)->ultimate_alias_target ();
+	  if (ultimate_node)
+	    return ultimate_node->decl;
 	}
     }
 

gcc/analyzer/supergraph.cc

@@ -56,6 +56,18 @@ along with GCC; see the file COPYING3.  If not see
 
 namespace ana {
 
+/* Get the function of the ultimate alias target being called at EDGE,
+   if any.  */
+
+static function *
+get_ultimate_function_for_cgraph_edge (cgraph_edge *edge)
+{
+  cgraph_node *ultimate_node = edge->callee->ultimate_alias_target ();
+  if (!ultimate_node)
+    return NULL;
+  return ultimate_node->get_fun ();
+}
+
 /* Get the cgraph_edge, but only if there's an underlying function body.  */
 
 cgraph_edge *
@@ -69,7 +81,7 @@ supergraph_call_edge (function *fun, gimple *stmt)
     return NULL;
   if (!edge->callee)
     return NULL; /* e.g. for a function pointer.  */
-  if (!edge->callee->get_fun ())
+  if (!get_ultimate_function_for_cgraph_edge (edge))
     return NULL;
   return edge;
 }
@@ -178,8 +190,10 @@ supergraph::supergraph (logger *logger)
 	{
 	  cgraph_edge *edge = (*iter).first;
 	  supernode *caller_prev_supernode = (*iter).second;
-	  basic_block callee_cfg_block
-	    = ENTRY_BLOCK_PTR_FOR_FN (edge->callee->get_fun ());
+	  function* callee_fn = get_ultimate_function_for_cgraph_edge (edge);
+	  if (!callee_fn || !callee_fn->cfg)
+	    continue;
+	  basic_block callee_cfg_block = ENTRY_BLOCK_PTR_FOR_FN (callee_fn);
 	  supernode *callee_supernode
 	    = *m_bb_to_initial_node.get (callee_cfg_block);
 	  call_superedge *sedge
@@ -199,8 +213,10 @@ supergraph::supergraph (logger *logger)
 	{
 	  cgraph_edge *edge = (*iter).first;
 	  supernode *caller_next_supernode = (*iter).second;
-	  basic_block callee_cfg_block
-	    = EXIT_BLOCK_PTR_FOR_FN (edge->callee->get_fun ());
+	  function* callee_fn = get_ultimate_function_for_cgraph_edge (edge);
+	  if (!callee_fn || !callee_fn->cfg)
+	    continue;
+	  basic_block callee_cfg_block = EXIT_BLOCK_PTR_FOR_FN (callee_fn);
 	  supernode *callee_supernode
 	    = *m_bb_to_initial_node.get (callee_cfg_block);
 	  return_superedge *sedge
@@ -840,7 +856,7 @@ callgraph_superedge::dump_label_to_pp (pretty_printer *pp,
 function *
 callgraph_superedge::get_callee_function () const
 {
-  return m_cedge->callee->get_fun ();
+  return get_ultimate_function_for_cgraph_edge (m_cedge);
 }
 
 /* Get the calling function at this interprocedural call/return edge.  */

gcc/analyzer/supergraph.h

@@ -156,7 +156,7 @@ public:
     return m_nodes[idx];
   }
 
-  unsigned get_num_snodes (function *fun) const
+  unsigned get_num_snodes (const function *fun) const
   {
     function_to_num_snodes_t &map
       = const_cast <function_to_num_snodes_t &>(m_function_to_num_snodes);
@@ -201,7 +201,7 @@ private:
   typedef ordered_hash_map<gimple *, supernode *> stmt_to_node_t;
   stmt_to_node_t m_stmt_to_node_t;
 
-  typedef hash_map<function *, unsigned> function_to_num_snodes_t;
+  typedef hash_map<const function *, unsigned> function_to_num_snodes_t;
   function_to_num_snodes_t m_function_to_num_snodes;
 };
 

gcc/testsuite/ChangeLog

@@ -1,3 +1,10 @@
+2020-02-11  David Malcolm  <dmalcolm@redhat.com>
+
+	PR analyzer/93288
+	* g++.dg/analyzer/malloc.C: Add test coverage for a double-free
+	called in a constructor.
+	* g++.dg/analyzer/pr93288.C: New test.
+
 2020-02-11  David Malcolm  <dmalcolm@redhat.com>
 
 	PR analyzer/93212

gcc/testsuite/g++.dg/analyzer/malloc.C

@@ -7,3 +7,19 @@ void test_1 (void *ptr)
   free (ptr);
   free (ptr); /* { dg-warning "double-'free' of 'ptr'" } */
 }
+
+/* Test of double-free in ctor.  */
+
+struct s2
+{
+  s2 (void *v)
+  {
+    free (v); // { dg-warning "double-'free' of 'v'" }
+  }
+};
+
+void test_2 (void *ptr)
+{
+  free (ptr); // { dg-message "first 'free' here" }
+  s2 a (ptr); // { dg-message "passing freed pointer 'ptr' in call to 's2::s2' from 'test_2'" }
+}

gcc/testsuite/g++.dg/analyzer/pr93288.C

@@ -0,0 +1,8 @@
+// { dg-do compile }
+
+struct a {
+  a();
+};
+class foo {
+  a b;
+} c;