Make filter_goto_model remove file local symbols

Since we want goto_harness to print out as little as possible to be
useful this is helpful, and this also lets us avoid bugs with duplicate
definitions (e.g. a static variable that’s now in the produced harness.c
– and thus a *different* static variable!).

Also marks non-file-local globals as extern so we avoid double
definitions.

Author: hannes-steffenhagen-diffblue

src/goto-harness/goto_harness_parse_options.cpp

@@ -51,12 +51,35 @@ static void filter_goto_model(
   goto_modelt &goto_model_with_harness,
   const std::unordered_set<irep_idt> &goto_model_without_harness_symbols)
 {
-  for(auto &symbol : goto_model_with_harness.get_symbol_table())
+  for(auto const &symbol_id : goto_model_without_harness_symbols)
   {
-    if(
-      goto_model_without_harness_symbols.count(symbol.first) == 1 &&
-      symbol.second.is_function())
-      goto_model_with_harness.unload(symbol.first);
+    auto &symbol =
+      goto_model_with_harness.symbol_table.get_writeable_ref(symbol_id);
+    if(symbol.is_function())
+    {
+      // We don’t want bodies of functions that already existed in the
+      // symbol table (i.e. not generated by us)
+      goto_model_with_harness.unload(symbol_id);
+      if(symbol.is_file_local)
+      {
+        goto_model_with_harness.symbol_table.remove(symbol_id);
+      }
+    }
+    else if(!symbol.is_type && symbol.is_file_local)
+    {
+      // We don’t want file local symbols from an existing goto model
+      // except types / typedefs, which also apparently get marked
+      // file local sometimes.
+      goto_model_with_harness.symbol_table.remove(symbol_id);
+    }
+    else if(!symbol.is_type && symbol.is_static_lifetime)
+    {
+      // if it has static lifetime and is *not* a type it is a global variable
+      // We keep around other global variables in case we want to initialise
+      // them, but mark them as extern so we don't duplicate their definitions
+      symbol.value = nil_exprt{};
+      symbol.is_extern = true;
+    }
   }
 }