Merge pull request diffblue#1781 from smowton/smowton/feature/java-create-stub-globals-earlier

 Java frontend: create synthetic static initialisers for stub globals

Author: smowton

regression/cbmc-java/generic_class_bound1/test.desc

@@ -7,5 +7,5 @@ Gn.class
 .*file Gn.java line 9 function java::Gn.foo1:\(LGn;\)V bytecode-index 1 block 1: FAILED
 .*file Gn.java line 10 function java::Gn.foo1:\(LGn;\)V bytecode-index 4 block 2: FAILED
 .*file Gn.java line 11 function java::Gn.foo1:\(LGn;\)V bytecode-index 5 block 3: FAILED
-.*file Gn.java line 13 function java::Gn.main:\(\[Ljava/lang/String;\)V bytecode-index 2 block 1: SATISFIED
+.*file Gn.java line 13 function java::Gn.main:\(\[Ljava/lang/String;\)V bytecode-index 2 block 2: SATISFIED
 --

src/java_bytecode/java_bytecode_convert_class.cpp

@@ -377,6 +377,10 @@ void java_bytecode_convert_classt::convert(
     new_symbol.name=id2string(class_symbol.name)+"."+id2string(f.name);
     new_symbol.base_name=f.name;
     new_symbol.type=field_type;
+    // Annotating the type with ID_C_class to provide a static field -> class
+    // link matches the method used by java_bytecode_convert_method::convert
+    // for methods.
+    new_symbol.type.set(ID_C_class, class_symbol.name);
     new_symbol.pretty_name=id2string(class_symbol.pretty_name)+
       "."+id2string(f.name);
     new_symbol.mode=ID_java;

src/java_bytecode/java_bytecode_convert_method.cpp

@@ -906,34 +906,6 @@ static void gather_symbol_live_ranges(
   }
 }
 
-/// See above
-/// \par parameters: `se`: Symbol expression referring to a static field
-/// `basename`: The static field's basename
-/// \return Creates a symbol table entry for the static field if one doesn't
-///   exist already.
-void java_bytecode_convert_methodt::check_static_field_stub(
-  const symbol_exprt &symbol_expr,
-  const irep_idt &basename)
-{
-  const auto &id=symbol_expr.get_identifier();
-  if(symbol_table.symbols.find(id)==symbol_table.symbols.end())
-  {
-    // Create a stub, to be overwritten if/when the real class is loaded.
-    symbolt new_symbol;
-    new_symbol.is_static_lifetime=true;
-    new_symbol.is_lvalue=true;
-    new_symbol.is_state_var=true;
-    new_symbol.name=id;
-    new_symbol.base_name=basename;
-    new_symbol.type=symbol_expr.type();
-    new_symbol.pretty_name=new_symbol.name;
-    new_symbol.mode=ID_java;
-    new_symbol.is_type=false;
-    new_symbol.value.make_nil();
-    symbol_table.add(new_symbol);
-  }
-}
-
 /// Each static access to classname should be prefixed with a check for
 /// necessary static init; this returns a call implementing that check.
 /// \param classname: Class name
@@ -2026,8 +1998,9 @@ codet java_bytecode_convert_methodt::convert_instructions(
         field_name.find("$assertionsDisabled")!=std::string::npos;
       symbol_expr.set_identifier(arg0.get_string(ID_class)+"."+field_name);
 
-      // If external, create a symbol table entry for this static field:
-      check_static_field_stub(symbol_expr, field_name);
+      INVARIANT(
+        symbol_table.has_symbol(symbol_expr.get_identifier()),
+        "getstatic symbol should have been created before method conversion");
 
       if(needed_lazy_methods)
       {
@@ -2081,8 +2054,9 @@ codet java_bytecode_convert_methodt::convert_instructions(
       const auto &field_name=arg0.get_string(ID_component_name);
       symbol_expr.set_identifier(arg0.get_string(ID_class)+"."+field_name);
 
-      // If external, create a symbol table entry for this static field:
-      check_static_field_stub(symbol_expr, field_name);
+      INVARIANT(
+        symbol_table.has_symbol(symbol_expr.get_identifier()),
+        "putstatic symbol should have been created before method conversion");
 
       if(needed_lazy_methods && arg0.type().id() == ID_symbol)
       {

src/java_bytecode/java_bytecode_convert_method_class.h

@@ -246,10 +246,6 @@ class java_bytecode_convert_methodt:public messaget
 
   const bytecode_infot &get_bytecode_info(const irep_idt &statement);
 
-  void check_static_field_stub(
-    const symbol_exprt &se,
-    const irep_idt &basename);
-
   bool class_needs_clinit(const irep_idt &classname);
   exprt get_or_create_clinit_wrapper(const irep_idt &classname);
   codet get_clinit_call(const irep_idt &classname);

src/java_bytecode/java_bytecode_language.cpp

@@ -223,7 +223,8 @@ static void infer_opaque_type_fields(
   namespacet ns(symbol_table);
   for(const auto &method : parse_tree.parsed_class.methods)
   {
-    for(const auto &instruction : method.instructions)
+    for(const java_bytecode_parse_treet::instructiont &instruction :
+          method.instructions)
     {
       if(instruction.statement == "getfield" ||
          instruction.statement == "putfield")
@@ -359,7 +360,8 @@ static void generate_constant_global_variables(
 {
   for(auto &method : parse_tree.parsed_class.methods)
   {
-    for(auto &instruction : method.instructions)
+    for(java_bytecode_parse_treet::instructiont &instruction :
+          method.instructions)
     {
       // ldc* instructions are Java bytecode "load constant" ops, which can
       // retrieve a numeric constant, String literal, or Class literal.
@@ -381,6 +383,87 @@ static void generate_constant_global_variables(
   }
 }
 
+/// Add a stub global symbol to the symbol table, initialising pointer-typed
+/// symbols with null and primitive-typed ones with an arbitrary (nondet) value.
+/// \param symbol_table: table to add to
+/// \param symbol_id: new symbol fully-qualified identifier
+/// \param symbol_basename: new symbol basename
+/// \param symbol_type: new symbol type
+/// \param class_id: class id that directly encloses this static field
+static void create_stub_global_symbol(
+  symbol_table_baset &symbol_table,
+  const irep_idt &symbol_id,
+  const irep_idt &symbol_basename,
+  const typet &symbol_type,
+  const irep_idt &class_id)
+{
+  symbolt new_symbol;
+  new_symbol.is_static_lifetime = true;
+  new_symbol.is_lvalue = true;
+  new_symbol.is_state_var = true;
+  new_symbol.name = symbol_id;
+  new_symbol.base_name = symbol_basename;
+  new_symbol.type = symbol_type;
+  new_symbol.type.set(ID_C_class, class_id);
+  new_symbol.pretty_name = new_symbol.name;
+  new_symbol.mode = ID_java;
+  new_symbol.is_type = false;
+  // If pointer-typed, initialise to null and a static initialiser will be
+  // created to initialise on first reference. If primitive-typed, specify
+  // nondeterministic initialisation by setting a nil value.
+  if(symbol_type.id() == ID_pointer)
+    new_symbol.value = null_pointer_exprt(to_pointer_type(symbol_type));
+  else
+    new_symbol.value.make_nil();
+  bool add_failed = symbol_table.add(new_symbol);
+  INVARIANT(
+    !add_failed, "caller should have checked symbol not already in table");
+}
+
+/// Search for getstatic and putstatic instructions in a class' bytecode and
+/// create stub symbols for any static fields that aren't already in the symbol
+/// table. The new symbols are null-initialised for reference-typed globals /
+/// static fields, and nondet-initialised for primitives.
+/// \param parse_tree: class bytecode
+/// \param symbol_table: symbol table; may gain new symbols
+static void create_stub_global_symbols(
+  const java_bytecode_parse_treet &parse_tree,
+  symbol_table_baset &symbol_table)
+{
+  namespacet ns(symbol_table);
+  for(const auto &method : parse_tree.parsed_class.methods)
+  {
+    for(const java_bytecode_parse_treet::instructiont &instruction :
+          method.instructions)
+    {
+      if(instruction.statement == "getstatic" ||
+         instruction.statement == "putstatic")
+      {
+        INVARIANT(
+          instruction.args.size() > 0,
+          "get/putstatic should have at least one argument");
+        irep_idt component = instruction.args[0].get_string(ID_component_name);
+        INVARIANT(
+          !component.empty(), "get/putstatic should specify a component");
+        irep_idt class_id = instruction.args[0].get_string(ID_class);
+        INVARIANT(
+          !class_id.empty(), "get/putstatic should specify a class");
+        irep_idt identifier = id2string(class_id) + "." + id2string(component);
+
+        if(!symbol_table.has_symbol(identifier))
+        {
+          create_stub_global_symbol(
+            symbol_table,
+            identifier,
+            component,
+            instruction.args[0].type(),
+            class_id);
+        }
+      }
+    }
+  }
+}
+
 bool java_bytecode_languaget::typecheck(
   symbol_tablet &symbol_table,
   const std::string &module)
@@ -477,10 +560,31 @@ bool java_bytecode_languaget::typecheck(
            << " String or Class constant symbols"
            << messaget::eom;
 
+  // For each reference to a stub global (that is, a global variable declared on
+  // a class we don't have bytecode for, and therefore don't know the static
+  // initialiser for), create a synthetic static initialiser (clinit method)
+  // to nondet initialise it.
+  // Note this must be done before making static initialiser wrappers below, as
+  // this makes a Classname.clinit method, then the next pass makes a wrapper
+  // that ensures it is only run once, and that static initialisation happens
+  // in class-graph topological order.
+
+  {
+    journalling_symbol_tablet symbol_table_journal =
+      journalling_symbol_tablet::wrap(symbol_table);
+    for(const auto &c : java_class_loader.class_map)
+    {
+      create_stub_global_symbols(c.second, symbol_table_journal);
+    }
+
+    stub_global_initializer_factory.create_stub_global_initializer_symbols(
+      symbol_table, symbol_table_journal.get_inserted(), synthetic_methods);
+  }
+
   // For each class that will require a static initializer wrapper, create a
   // function named package.classname::clinit_wrapper, and a corresponding
   // global tracking whether it has run or not:
-  create_static_initializer_wrappers(symbol_table);
+  create_static_initializer_wrappers(symbol_table, synthetic_methods);
 
   // Now incrementally elaborate methods
   // that are reachable from this entry point.
@@ -495,24 +599,12 @@ bool java_bytecode_languaget::typecheck(
     journalling_symbol_tablet journalling_symbol_table =
       journalling_symbol_tablet::wrap(symbol_table);
 
+    // Convert all synthetic methods:
+    for(const auto &function_id_and_type : synthetic_methods)
     {
-      // Convert all static initialisers:
-      std::vector<irep_idt> static_initialisers;
-
-      // Careful not to add symbols while iterating over the symbol table!
-      for(const auto &symbol : symbol_table.symbols)
-      {
-        if(is_clinit_wrapper_function(symbol.second.name))
-          static_initialisers.push_back(symbol.second.name);
-      }
-
-      for(const auto &static_init_wrapper_name : static_initialisers)
-      {
-        convert_single_method(
-          static_init_wrapper_name, journalling_symbol_table);
-      }
+      convert_single_method(
+        function_id_and_type.first, journalling_symbol_table);
     }
-
     // Convert all methods for which we have bytecode now
     for(const auto &method_sig : method_bytecode)
     {
@@ -714,6 +806,8 @@ bool java_bytecode_languaget::convert_single_method(
   // Get bytecode for specified function if we have it
   method_bytecodet::opt_reft cmb = method_bytecode.get(function_id);
 
+  synthetic_methods_mapt::iterator synthetic_method_it;
+
   // Check if have a string solver implementation
   if(string_preprocess.implements_function(function_id))
   {
@@ -735,11 +829,29 @@ bool java_bytecode_languaget::convert_single_method(
     symbol.value = generated_code;
     return false;
   }
-  else if(is_clinit_wrapper_function(function_id))
+  else if(
+    (synthetic_method_it = synthetic_methods.find(function_id)) !=
+    synthetic_methods.end())
   {
+    // Synthetic method (i.e. one generated by the Java frontend and which
+    // doesn't occur in the source bytecode):
     symbolt &symbol = symbol_table.get_writeable_ref(function_id);
-    symbol.value = get_clinit_wrapper_body(function_id, symbol_table);
-    // Notify lazy methods of other static init functions called:
+    switch(synthetic_method_it->second)
+    {
+    case synthetic_method_typet::STATIC_INITIALIZER_WRAPPER:
+      symbol.value = get_clinit_wrapper_body(function_id, symbol_table);
+      break;
+    case synthetic_method_typet::STUB_CLASS_STATIC_INITIALIZER:
+      symbol.value =
+        stub_global_initializer_factory.get_stub_initializer_body(
+          function_id,
+          symbol_table,
+          object_factory_parameters,
+          get_pointer_type_selector());
+      break;
+    }
+    // Notify lazy methods of static calls made from the newly generated
+    // function:
     notify_static_method_calls(symbol.value, needed_lazy_methods);
     return false;
   }

src/java_bytecode/java_bytecode_language.h

@@ -19,7 +19,10 @@ Author: Daniel Kroening, [email protected]
 #include "ci_lazy_methods.h"
 #include "ci_lazy_methods_needed.h"
 #include "java_class_loader.h"
+#include "java_static_initializers.h"
 #include "java_string_library_preprocess.h"
+#include "object_factory_parameters.h"
+#include "synthetic_methods_map.h"
 
 #include <java_bytecode/select_pointer_type.h>
 
@@ -53,10 +56,6 @@ Author: Daniel Kroening, [email protected]
   "                                  the purpose of lazy method loading\n"                       /* NOLINT(*) */ \
   "                                  A '.*' wildcard is allowed to specify all class members\n"
 
-#define MAX_NONDET_ARRAY_LENGTH_DEFAULT 5
-#define MAX_NONDET_STRING_LENGTH std::numeric_limits<std::int32_t>::max()
-#define MAX_NONDET_TREE_DEPTH 5
-
 class symbolt;
 
 enum lazy_methods_modet
@@ -66,26 +65,6 @@ enum lazy_methods_modet
   LAZY_METHODS_MODE_CONTEXT_SENSITIVE
 };
 
-struct object_factory_parameterst final
-{
-  /// Maximum value for the non-deterministically-chosen length of an array.
-  size_t max_nondet_array_length=MAX_NONDET_ARRAY_LENGTH_DEFAULT;
-
-  /// Maximum value for the non-deterministically-chosen length of a string.
-  size_t max_nondet_string_length=MAX_NONDET_STRING_LENGTH;
-
-  /// Maximum depth for object hierarchy on input.
-  /// Used to prevent object factory to loop infinitely during the
-  /// generation of code that allocates/initializes data structures of recursive
-  /// data types or unbounded depth. We bound the maximum number of times we
-  /// dereference a pointer using a 'depth counter'. We set a pointer to null if
-  /// such depth becomes >= than this maximum value.
-  size_t max_nondet_tree_depth=MAX_NONDET_TREE_DEPTH;
-
-  /// Force string content to be ASCII printable characters when set to true.
-  bool string_printable = false;
-};
-
 class java_bytecode_languaget:public languaget
 {
 public:
@@ -192,6 +171,8 @@ class java_bytecode_languaget:public languaget
 
 private:
   const std::unique_ptr<const select_pointer_typet> pointer_type_selector;
+  synthetic_methods_mapt synthetic_methods;
+  stub_global_initializer_factoryt stub_global_initializer_factory;
 };
 
 std::unique_ptr<languaget> new_java_bytecode_language();

src/java_bytecode/java_entry_point.cpp

@@ -82,17 +82,6 @@ static bool should_init_symbol(const symbolt &sym)
   return is_java_string_literal_id(sym.name);
 }
 
-static bool is_non_null_library_global(const irep_idt &symbolid)
-{
-  static const std::unordered_set<irep_idt, irep_id_hash> non_null_globals=
-  {
-    "java::java.lang.System.out",
-    "java::java.lang.System.err",
-    "java::java.lang.System.in"
-  };
-  return non_null_globals.count(symbolid);
-}
-
 static void java_static_lifetime_init(
   symbol_table_baset &symbol_table,
   const source_locationt &source_location,
@@ -129,8 +118,6 @@ static void java_static_lifetime_init(
             allow_null=false;
           if(allow_null && is_java_string_literal_id(nameid))
             allow_null=false;
-          if(allow_null && is_non_null_library_global(nameid))
-            allow_null=false;
         }
         gen_nondet_init(
           sym.symbol_expr(),