Add static analysis hook for unavailable functions

This enables a subclass to supply behaviour when a function isn't
loaded (i.e. its value is nil), rather than always ignore such
callsites.

Author: smowton

src/analyses/static_analysis.cpp

@@ -422,8 +422,12 @@ void static_analysis_baset::do_function_call(
 {
   const goto_functionst::goto_functiont &goto_function=f_it->second;
 
-  if(!goto_function.body_available())
-    return; // do nothing
+  if((!goto_function.body_available()) || !should_enter_function(f_it->first))
+  {
+    // Per default do nothing, but a subclass might transform across the stubbed callsite.
+    transform_function_stub(f_it->first,new_state,l_call,l_return);
+    return;
+  }
 
   assert(!goto_function.body.instructions.empty());
 

src/analyses/static_analysis.h

@@ -244,6 +244,9 @@ class static_analysis_baset
     const exprt::operandst &arguments,
     statet &new_state);
 
+  virtual bool should_enter_function(const irep_idt&) { return true; }
+  virtual void transform_function_stub(const irep_idt&, statet& state, locationt l_call, locationt l_return) {}
+
   // abstract methods
 
   virtual void generate_state(locationt l)=0;