Constify collect_virtual_function_callees

This was always a const operation in spirit, as it retrieves a set of potential virtual function
overrides without making any changes to the GOTO program, but was recently changed to take a non-
const symbol table because it shares code with remove_virtual_function(s), which indeed add new
symbols to the symbol table.

To once again allow calling collect_virtual_function_callees in a const context, this splits the
implementation of remove_virtual_functions into those parts that require a non-const reference and
those for which a const symbol table will suffice.

Author: smowton

src/goto-programs/remove_virtual_functions.cpp

@@ -22,62 +22,76 @@ Author: Daniel Kroening, [email protected]
 #include "remove_skip.h"
 #include "resolve_inherited_component.h"
 
-class remove_virtual_functionst
+class get_virtual_calleest
 {
 public:
-  remove_virtual_functionst(
-    symbol_table_baset &_symbol_table,
-    const class_hierarchyt &_class_hierarchy);
-
-  void operator()(goto_functionst &goto_functions);
-
-  bool remove_virtual_functions(
-    const irep_idt &function_id,
-    goto_programt &goto_program);
-
-  goto_programt::targett remove_virtual_function(
-    const irep_idt &function_id,
-    goto_programt &goto_program,
-    goto_programt::targett target,
-    const dispatch_table_entriest &functions,
-    virtual_dispatch_fallback_actiont fallback_action);
+  get_virtual_calleest(
+    const symbol_table_baset &_symbol_table,
+    const class_hierarchyt &_class_hierarchy) :
+    ns(_symbol_table),
+    symbol_table(_symbol_table),
+    class_hierarchy(_class_hierarchy)
+  {
+  }
 
-  void get_functions(const exprt &, dispatch_table_entriest &);
+  void get_functions(const exprt &, dispatch_table_entriest &) const;
 
 protected:
   const namespacet ns;
-  symbol_table_baset &symbol_table;
+  const symbol_table_baset &symbol_table;
 
   const class_hierarchyt &class_hierarchy;
 
-  goto_programt::targett remove_virtual_function(
-    const irep_idt &function_id,
-    goto_programt &goto_program,
-    goto_programt::targett target);
   typedef std::function<
     optionalt<resolve_inherited_componentt::inherited_componentt>(
       const irep_idt &,
       const irep_idt &)>
     function_call_resolvert;
+
   void get_child_functions_rec(
     const irep_idt &,
     const optionalt<symbol_exprt> &,
     const irep_idt &,
     dispatch_table_entriest &,
     dispatch_table_entries_mapt &,
     const function_call_resolvert &) const;
+
   exprt
   get_method(const irep_idt &class_id, const irep_idt &component_name) const;
 };
 
-remove_virtual_functionst::remove_virtual_functionst(
-  symbol_table_baset &_symbol_table,
-  const class_hierarchyt &_class_hierarchy)
-  : ns(_symbol_table),
-    symbol_table(_symbol_table),
-    class_hierarchy(_class_hierarchy)
+class remove_virtual_functionst : public get_virtual_calleest
 {
-}
+public:
+  remove_virtual_functionst(
+    symbol_table_baset &_symbol_table,
+    const class_hierarchyt &_class_hierarchy) :
+    get_virtual_calleest(_symbol_table, _class_hierarchy),
+    symbol_table(_symbol_table)
+  {
+  }
+
+  void operator()(goto_functionst &functions);
+
+  bool remove_virtual_functions(
+    const irep_idt &function_id,
+    goto_programt &goto_program);
+
+  goto_programt::targett remove_virtual_function(
+    const irep_idt &function_id,
+    goto_programt &goto_program,
+    goto_programt::targett target,
+    const dispatch_table_entriest &functions,
+    virtual_dispatch_fallback_actiont fallback_action);
+
+protected:
+  symbol_table_baset &symbol_table;
+
+  goto_programt::targett remove_virtual_function(
+    const irep_idt &function_id,
+    goto_programt &goto_program,
+    goto_programt::targett target);
+};
 
 /// Replace specified virtual function call with a static call to its
 /// most derived implementation
@@ -497,7 +511,7 @@ goto_programt::targett remove_virtual_functionst::remove_virtual_function(
 ///   -> [{"C", C.f}, {"B", C.f}, {"A", A.f}]
 /// \param entry_map: map of class identifiers to dispatch table entries
 /// \param resolve_function_call`: function to resolve abstract method call
-void remove_virtual_functionst::get_child_functions_rec(
+void get_virtual_calleest::get_child_functions_rec(
   const irep_idt &this_id,
   const optionalt<symbol_exprt> &last_method_defn,
   const irep_idt &component_name,
@@ -565,9 +579,9 @@ void remove_virtual_functionst::get_child_functions_rec(
 /// \param function: function that should be called
 /// \param [out] functions: is assigned a list of dispatch entries, i.e., pairs
 ///   of class names and function symbol to call when encountering the class.
-void remove_virtual_functionst::get_functions(
+void get_virtual_calleest::get_functions(
   const exprt &function,
-  dispatch_table_entriest &functions)
+  dispatch_table_entriest &functions) const
 {
   // class part of function to call
   const irep_idt class_id=function.get(ID_C_class);
@@ -650,7 +664,7 @@ void remove_virtual_functionst::get_functions(
 /// \param component_name: Name of the function to look up
 /// \return nil_exprt instance on error and a symbol_exprt pointing to
 ///   the method on success
-exprt remove_virtual_functionst::get_method(
+exprt get_virtual_calleest::get_method(
   const irep_idt &class_id,
   const irep_idt &component_name) const
 {
@@ -808,10 +822,10 @@ goto_programt::targett remove_virtual_function(
 
 void collect_virtual_function_callees(
   const exprt &function,
-  symbol_table_baset &symbol_table,
+  const symbol_table_baset &symbol_table,
   const class_hierarchyt &class_hierarchy,
   dispatch_table_entriest &overridden_functions)
 {
-  remove_virtual_functionst instance(symbol_table, class_hierarchy);
-  instance.get_functions(function, overridden_functions);
+  get_virtual_calleest get_callees(symbol_table, class_hierarchy);
+  get_callees.get_functions(function, overridden_functions);
 }

src/goto-programs/remove_virtual_functions.h

@@ -114,7 +114,7 @@ goto_programt::targett remove_virtual_function(
 ///   overridden functions will be stored.
 void collect_virtual_function_callees(
   const exprt &function,
-  symbol_tablet &symbol_table,
+  const symbol_table_baset &symbol_table,
   const class_hierarchyt &class_hierarchy,
   dispatch_table_entriest &overridden_functions);