Made generate_start_function abstract

Made the generat_start_function abstract to ensure new langugages are at
least aware they should provide implemention for this method. CPP and
JSIL languages have stub method that asserts for now.

Author: thk123

src/cpp/cpp_language.cpp

@@ -53,6 +53,22 @@ void cpp_languaget::modules_provided(std::set<std::string> &modules)
   modules.insert(get_base_name(parse_path, true));
 }
 
+/// Generate a _start function for a specific function
+/// \param entry_function_symbol: The symbol for the function that should be
+///   used as the entry point
+/// \param symbol_table: The symbol table for the program. The new _start
+///   function symbol will be added to this table
+/// \return Returns false if the _start method was generated correctly
+bool cpp_languaget::generate_start_function(
+  const symbolt &entry_function_symbol,
+  symbol_tablet &symbol_table)
+{
+  return generate_ansi_c_start_function(
+    entry_function_symbol,
+    symbol_table,
+    *message_handler);
+}
+
 /// ANSI-C preprocessing
 bool cpp_languaget::preprocess(
   std::istream &instream,

src/cpp/cpp_language.h

@@ -85,6 +85,10 @@ class cpp_languaget:public languaget
 
   void modules_provided(std::set<std::string> &modules) override;
 
+  virtual bool generate_start_function(
+    const class symbolt &entry_function_symbol,
+    class symbol_tablet &symbol_table) override;
+
 protected:
   cpp_parse_treet cpp_parse_tree;
   std::string parse_path;

src/jsil/jsil_language.cpp

@@ -41,6 +41,22 @@ bool jsil_languaget::interfaces(symbol_tablet &symbol_table)
   return false;
 }
 
+/// Generate a _start function for a specific function
+/// \param entry_function_symbol: The symbol for the function that should be
+///   used as the entry point
+/// \param symbol_table: The symbol table for the program. The new _start
+///   function symbol will be added to this table
+/// \return Returns false if the _start method was generated correctly
+bool jsil_languaget::generate_start_function(
+  const symbolt &entry_function_symbol,
+  symbol_tablet &symbol_table)
+{
+  // TODO(tkiley): This should be implemented if this language
+  // is used.
+  UNREACHABLE;
+  return true;
+}
+
 bool jsil_languaget::preprocess(
   std::istream &instream,
   const std::string &path,

src/jsil/jsil_language.h

@@ -69,6 +69,10 @@ class jsil_languaget:public languaget
   virtual void modules_provided(std::set<std::string> &modules);
   virtual bool interfaces(symbol_tablet &symbol_table);
 
+  virtual bool generate_start_function(
+    const class symbolt &entry_function_symbol,
+    class symbol_tablet &symbol_table) override;
+
 protected:
   jsil_parse_treet parse_tree;
   std::string parse_path;

src/util/language.cpp

@@ -191,20 +191,3 @@ void languaget::generate_opaque_parameter_symbols(
     symbol_table.add(param_symbol);
   }
 }
-
-/// Generate a entry function for a specific function. Should be overriden in
-/// derived languagets
-/// \param entry_function_symbol: The symbol for the function that should be
-///   used as the entry point
-/// \param symbol_table: The symbol table for the program. The new _start
-///   function symbol will be added to this table
-/// \return Returns false if the entry method was generated correctly
-bool languaget::generate_start_function(
-  const symbolt &entry_function_symbol,
-  symbol_tablet &symbol_table)
-{
-  // Implement in derived languagets
-  assert(0);
-  return true;
-}
-

src/util/language.h

@@ -121,7 +121,7 @@ class languaget:public messaget
 
   virtual bool generate_start_function(
     const class symbolt &entry_function_symbol,
-    class symbol_tablet &symbol_table);
+    class symbol_tablet &symbol_table)=0;
 
   // constructor / destructor