Package org.plumelib.bcelutil

Class StackMapUtils

  • Direct Known Subclasses:
    InstructionListUtils
    public abstract class StackMapUtils
extends Object
    This class provides utility methods to maintain and modify a method's StackMapTable within a Java class file. It can be thought of as an extension to BCEL.

    BCEL ought to automatically build and maintain the StackMapTable in a manner similar to the LineNumberTable and the LocalVariableTable. However, for historical reasons, it does not.

    This class cannot be a set of static methods (like BcelUtil) as it maintains state during the client's processing of a method that must be available on a per thread basis. Thus it is an abstract class extended by InstructionListUtils. A client would not normally extend this class directly.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected SimpleLog debug_instrument
      A log to which to print debugging information about program instrumentation.
      private org.apache.bcel.classfile.StackMapEntry @InternedDistinct [] empty_stack_map_table
      An empty StackMap used for initialization.
      protected int first_local_index
      The index of the first 'true' local in the local variable table.
      protected int initial_locals_count
      The number of local variables in the current method prior to any modifications.
      protected org.apache.bcel.classfile.StackMapType @MonotonicNonNull [] initial_type_list
      Initial state of StackMapTypes for locals on method entry.
      protected boolean needStackMap
      Whether or not the current method needs a StackMap; set by set_current_stack_map_table.
      protected @org.checkerframework.checker.index.qual.NonNegative int number_active_locals
      A number of methods in this class search and locate a particular StackMap within the current method.
      protected @Nullable org.apache.bcel.generic.ConstantPoolGen pool
      The pool for the method currently being processed.
      protected int running_offset
      Offset into code that corresponds to the current StackMap of interest.
      protected @Nullable org.apache.bcel.classfile.StackMap smta
      Original stack map table attribute; set by set_current_stack_map_table.
      protected org.apache.bcel.classfile.StackMapEntry @Nullable [] stack_map_table
      Working copy of StackMapTable; set by set_current_stack_map_table.
      private Map<org.apache.bcel.generic.InstructionHandle,​Integer> uninitialized_NEW_map
      A map from instructions that create uninitialized NEW objects to the corresponding StackMap entry.

    • Constructor Summary

      Constructors 
      Constructor Description
      StackMapUtils()  

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods 
      Modifier and Type Method Description
      protected org.apache.bcel.generic.LocalVariableGen add_new_argument​(org.apache.bcel.generic.MethodGen mgen, String arg_name, org.apache.bcel.generic.Type arg_type)
      Deprecated.
      use add_new_parameter(org.apache.bcel.generic.MethodGen, java.lang.String, org.apache.bcel.generic.Type)
      protected org.apache.bcel.generic.LocalVariableGen add_new_parameter​(org.apache.bcel.generic.MethodGen mgen, String arg_name, org.apache.bcel.generic.Type arg_type)
      Add a new parameter to the method.
      protected String[] add_string​(String[] arr, String new_string)
      Returns a String array with new_string added to the end of arr.
      protected void adjust_code_for_locals_change​(org.apache.bcel.generic.MethodGen mgen, int index_first_moved_local, int size)
      Process the instruction list, adding size (1 or 2) to the index of each Instruction that references a local that is equal or higher in the local map than index_first_moved_local.
      protected StackTypes bcel_calc_stack_types​(org.apache.bcel.generic.MethodGen mg)
      Calculates the types on the stack for each instruction using the BCEL stack verification routines.
      protected void build_unitialized_NEW_map​(org.apache.bcel.generic.InstructionList il)
      We need to locate and remember any NEW instructions that create uninitialized objects.
      protected org.apache.bcel.generic.LocalVariableGen create_method_scope_local​(org.apache.bcel.generic.MethodGen mgen, String local_name, org.apache.bcel.generic.Type local_type)
      Create a new local with a scope of the full method.
      protected void create_new_stack_map_attribute​(org.apache.bcel.generic.MethodGen mgen)
      Create a new StackMap code attribute from stack_map_table.
      protected void fetch_current_stack_map_table​(org.apache.bcel.generic.MethodGen mgen, int java_class_version)
      Deprecated.
      use set_current_stack_map_table(org.apache.bcel.generic.MethodGen, int)
      protected org.apache.bcel.classfile.StackMapEntry find_stack_map_equal​(int offset)
      Find the StackMap entry whose offset matches the input argument.
      protected @org.checkerframework.checker.index.qual.IndexOrLow({"stack_map_table"}) int find_stack_map_index_after​(int offset)
      Find the index of the StackMap entry whose offset is the first one after the input argument.
      protected int find_stack_map_index_before​(int offset)
      Find the index of the StackMap entry whose offset is the last one before the input argument.
      protected void fix_local_variable_table​(org.apache.bcel.generic.MethodGen mgen)
      Under some circumstances, there may be problems with the local variable table.
      protected int gen_temp_locals​(org.apache.bcel.generic.MethodGen mgen, int offset)
      Find the live range of the compiler temp(s) at the given offset and create a LocalVariableGen for each.
      protected org.apache.bcel.classfile.StackMapType generate_StackMapType_from_Type​(org.apache.bcel.generic.Type t)
      Convert a Type to a StackMapType.
      protected org.apache.bcel.generic.Type generate_Type_from_StackMapType​(org.apache.bcel.classfile.StackMapType smt)
      Convert a StackMapType to a Type.
      protected String get_attribute_name​(org.apache.bcel.classfile.Attribute a)
      Return the attribute name for the specified attribute.
      protected @Nullable org.apache.bcel.classfile.Attribute get_local_variable_type_table_attribute​(org.apache.bcel.generic.MethodGen mgen)
      Find the LocalVariableTypeTable attribute for a method.
      protected @Nullable org.apache.bcel.classfile.Attribute get_stack_map_table_attribute​(org.apache.bcel.generic.MethodGen mgen)
      Find the StackMapTable attribute for a method.
      protected int getSize​(org.apache.bcel.classfile.StackMapType smt)
      Return the operand size of this type (2 for long and double, 1 otherwise).
      protected boolean is_local_variable_type_table​(org.apache.bcel.classfile.Attribute a)
      Returns whether or not the specified attribute is a LocalVariableTypeTable.
      protected boolean is_stack_map_table​(org.apache.bcel.classfile.Attribute a)
      Returns whether or not the specified attribute is a StackMapTable.
      protected void modify_stack_maps_for_switches​(org.apache.bcel.generic.InstructionHandle ih, org.apache.bcel.generic.InstructionList il)
      Check to see if (due to some instruction modifications) there have been any changes in a switch statement's padding bytes.
      protected void print_stack_map_table​(String prefix)
      Print the contents of the StackMapTable to the debug_instrument.log.
      protected void remove_local_variable_type_table​(org.apache.bcel.generic.MethodGen mgen)
      Remove the local variable type table attribute (LVTT) from mgen.
      protected void set_current_stack_map_table​(org.apache.bcel.generic.MethodGen mgen, int java_class_version)
      Get existing StackMapTable from the MethodGen argument.
      protected static @ClassGetName String typeToClassGetName​(org.apache.bcel.generic.Type t)
      Convert a Type name to a Class name.
      protected void update_full_frame_stack_map_entries​(int offset, org.apache.bcel.generic.Type type_new_var, org.apache.bcel.generic.LocalVariableGen[] locals)
      Update any FULL_FRAME StackMap entries to include a new local var.
      private void update_NEW_object_stack_map_entries​(int old_offset, int new_offset)
      One of uninitialized NEW instructions has moved.
      protected void update_stack_map_offset​(int position, int delta)
      We have inserted additional byte(s) into the instruction list; update the StackMaps, if required.
      protected void update_uninitialized_NEW_offsets​(org.apache.bcel.generic.InstructionList il)
      Check to see if any of the uninitialized NEW instructions have moved.

    • Field Detail

      • pool

        protected @Nullable org.apache.bcel.generic.ConstantPoolGen pool
        The pool for the method currently being processed. Must be set by the client. See the sample code in InstructionListUtils for when and how to set this value.

      • debug_instrument

        protected SimpleLog debug_instrument
        A log to which to print debugging information about program instrumentation.

      • needStackMap

        protected boolean needStackMap
        Whether or not the current method needs a StackMap; set by set_current_stack_map_table.

      • stack_map_table

        protected org.apache.bcel.classfile.StackMapEntry @Nullable [] stack_map_table
        Working copy of StackMapTable; set by set_current_stack_map_table.

      • smta

        protected @Nullable org.apache.bcel.classfile.StackMap smta
        Original stack map table attribute; set by set_current_stack_map_table.

      • initial_type_list

        protected org.apache.bcel.classfile.StackMapType @MonotonicNonNull [] initial_type_list
        Initial state of StackMapTypes for locals on method entry.

      • initial_locals_count

        protected int initial_locals_count
        The number of local variables in the current method prior to any modifications.

      • number_active_locals

        protected @org.checkerframework.checker.index.qual.NonNegative int number_active_locals
        A number of methods in this class search and locate a particular StackMap within the current method. This variable contains the number of live local variables within the range of byte code instructions covered by this StackMap. Set by update_stack_map_offset, find_stack_map_equal, find_stack_map_index_before, or find_stack_map_index_after.

      • running_offset

        protected int running_offset
        Offset into code that corresponds to the current StackMap of interest. Set by find_stack_map_index_before.

      • first_local_index

        protected int first_local_index
        The index of the first 'true' local in the local variable table. That is, after 'this' and any parameters.

      • empty_stack_map_table

        private org.apache.bcel.classfile.StackMapEntry @InternedDistinct [] empty_stack_map_table
        An empty StackMap used for initialization.

      • uninitialized_NEW_map

        private Map<org.apache.bcel.generic.InstructionHandle,​Integer> uninitialized_NEW_map
        A map from instructions that create uninitialized NEW objects to the corresponding StackMap entry. Set by build_unitialized_NEW_map.

    • Constructor Detail

      • StackMapUtils

        public StackMapUtils()

    • Method Detail

      • add_string

        protected String[] add_string​(String[] arr,
                              String new_string)
        Returns a String array with new_string added to the end of arr.
        Parameters:
        arr - original string array
        new_string - string to be added
        Returns:
        the new string array

      • get_attribute_name

        @Pure
protected final String get_attribute_name​(org.apache.bcel.classfile.Attribute a)
        Return the attribute name for the specified attribute.
        Parameters:
        a - the attribute
        Returns:
        the attribute name for the specified attribute

      • is_local_variable_type_table

        @Pure
protected final boolean is_local_variable_type_table​(org.apache.bcel.classfile.Attribute a)
        Returns whether or not the specified attribute is a LocalVariableTypeTable.
        Parameters:
        a - the attribute
        Returns:
        true iff the attribute is a LocalVariableTypeTable

      • is_stack_map_table

        @Pure
protected final boolean is_stack_map_table​(org.apache.bcel.classfile.Attribute a)
        Returns whether or not the specified attribute is a StackMapTable.
        Parameters:
        a - the attribute
        Returns:
        true iff the attribute is a StackMapTable

      • get_stack_map_table_attribute

        @Pure
protected final @Nullable org.apache.bcel.classfile.Attribute get_stack_map_table_attribute​(org.apache.bcel.generic.MethodGen mgen)
        Find the StackMapTable attribute for a method. Return null if there isn't one.
        Parameters:
        mgen - the method
        Returns:
        the StackMapTable attribute for the method (or null if not present)

      • get_local_variable_type_table_attribute

        @Pure
protected final @Nullable org.apache.bcel.classfile.Attribute get_local_variable_type_table_attribute​(org.apache.bcel.generic.MethodGen mgen)
        Find the LocalVariableTypeTable attribute for a method. Return null if there isn't one.
        Parameters:
        mgen - the method
        Returns:
        the LocalVariableTypeTable attribute for the method (or null if not present)

      • remove_local_variable_type_table

        protected final void remove_local_variable_type_table​(org.apache.bcel.generic.MethodGen mgen)
        Remove the local variable type table attribute (LVTT) from mgen. Some instrumentation changes require this to be updated, but without BCEL support that would be hard to do. It should be safe to just delete it since it is optional and really only of use to a debugger.
        Parameters:
        mgen - the method to clear out

      • update_stack_map_offset

        protected final void update_stack_map_offset​(int position,
                                             int delta)
        We have inserted additional byte(s) into the instruction list; update the StackMaps, if required. Also sets running_offset.
        Parameters:
        position - the location of insertion
        delta - the size of the insertion

      • find_stack_map_equal

        protected final org.apache.bcel.classfile.StackMapEntry find_stack_map_equal​(int offset)
        Find the StackMap entry whose offset matches the input argument. Also sets running_offset.
        Parameters:
        offset - byte code offset
        Returns:
        the corresponding StackMapEntry

      • find_stack_map_index_before

        protected final int find_stack_map_index_before​(int offset)
        Find the index of the StackMap entry whose offset is the last one before the input argument. Return -1 if there isn't one. Also sets running_offset and number_active_locals.
        Parameters:
        offset - byte code offset
        Returns:
        the corresponding StackMapEntry index

      • find_stack_map_index_after

        protected final @org.checkerframework.checker.index.qual.IndexOrLow({"stack_map_table"}) int find_stack_map_index_after​(int offset)
        Find the index of the StackMap entry whose offset is the first one after the input argument. Return -1 if there isn't one. Also sets running_offset.
        Parameters:
        offset - byte code offset
        Returns:
        the corresponding StackMapEntry index

      • modify_stack_maps_for_switches

        protected final void modify_stack_maps_for_switches​(org.apache.bcel.generic.InstructionHandle ih,
                                                    org.apache.bcel.generic.InstructionList il)
        Check to see if (due to some instruction modifications) there have been any changes in a switch statement's padding bytes. If so, then update the corresponding StackMap to reflect this change.
        Parameters:
        ih - where to start looking for a switch instruction
        il - instruction list to search

      • gen_temp_locals

        @RequiresNonNull("initial_type_list")
protected final int gen_temp_locals​(org.apache.bcel.generic.MethodGen mgen,
                                    int offset)
        Find the live range of the compiler temp(s) at the given offset and create a LocalVariableGen for each. Note the compiler might generate temps of different sizes at the same offset (must have disjoint lifetimes).
        Parameters:
        mgen - the method
        offset - compiler assigned local offset of hidden temp
        Returns:
        offset incremented by size of smallest temp found at offset

      • build_unitialized_NEW_map

        protected final void build_unitialized_NEW_map​(org.apache.bcel.generic.InstructionList il)
        We need to locate and remember any NEW instructions that create uninitialized objects. Their offset may be contained in a StackMap entry and will probably need to be updated as we add instrumentation code. Note that these instructions are fairly rare.
        Parameters:
        il - instruction list to search

      • update_NEW_object_stack_map_entries

        private final void update_NEW_object_stack_map_entries​(int old_offset,
                                                       int new_offset)
        One of uninitialized NEW instructions has moved. Update its offset in StackMap entries. Note that more than one entry could refer to the same instruction. This is a helper routine used by update_uninitialized_NEW_offsets.
        Parameters:
        old_offset - original location of NEW instruction
        new_offset - new location of NEW instruction

      • update_uninitialized_NEW_offsets

        protected final void update_uninitialized_NEW_offsets​(org.apache.bcel.generic.InstructionList il)
        Check to see if any of the uninitialized NEW instructions have moved. Again, these are rare, so a linear pass is fine.
        Parameters:
        il - instruction list to search

      • adjust_code_for_locals_change

        protected final void adjust_code_for_locals_change​(org.apache.bcel.generic.MethodGen mgen,
                                                   int index_first_moved_local,
                                                   int size)
        Process the instruction list, adding size (1 or 2) to the index of each Instruction that references a local that is equal or higher in the local map than index_first_moved_local. Size should be the size of the new local that was just inserted at index_first_moved_local.
        Parameters:
        mgen - MethodGen to be modified
        index_first_moved_local - original index of first local moved "up"
        size - size of new local added (1 or 2)

      • fetch_current_stack_map_table

        @Deprecated
protected final void fetch_current_stack_map_table​(org.apache.bcel.generic.MethodGen mgen,
                                                   int java_class_version)
        Deprecated.
        use set_current_stack_map_table(org.apache.bcel.generic.MethodGen, int)
        Get existing StackMapTable from the MethodGen argument. If there is none, create a new empty one. Sets both smta and stack_map_table. Must be called prior to any other methods that manipulate the stack_map_table!
        Parameters:
        mgen - MethodGen to search
        java_class_version - Java version for the classfile; stack_map_table is optional before Java 1.7 (= classfile version 51)

      • set_current_stack_map_table

        @EnsuresNonNull("stack_map_table")
protected final void set_current_stack_map_table​(org.apache.bcel.generic.MethodGen mgen,
                                                 int java_class_version)
        Get existing StackMapTable from the MethodGen argument. If there is none, create a new empty one. Sets both smta and stack_map_table. Must be called prior to any other methods that manipulate the stack_map_table!
        Parameters:
        mgen - MethodGen to search
        java_class_version - Java version for the classfile; stack_map_table is optional before Java 1.7 (= classfile version 51)

      • print_stack_map_table

        protected final void print_stack_map_table​(String prefix)
        Print the contents of the StackMapTable to the debug_instrument.log.
        Parameters:
        prefix - label to display with table

      • create_new_stack_map_attribute

        protected final void create_new_stack_map_attribute​(org.apache.bcel.generic.MethodGen mgen)
                                             throws IOException
        Create a new StackMap code attribute from stack_map_table.
        Parameters:
        mgen - MethodGen to add attribute to
        Throws:
        IOException - if cannot create the attribute

      • typeToClassGetName

        protected static @ClassGetName String typeToClassGetName​(org.apache.bcel.generic.Type t)
        Convert a Type name to a Class name.
        Parameters:
        t - type whose name is to be converted
        Returns:
        a String containing the class name

      • generate_StackMapType_from_Type

        protected final org.apache.bcel.classfile.StackMapType generate_StackMapType_from_Type​(org.apache.bcel.generic.Type t)
        Convert a Type to a StackMapType.
        Parameters:
        t - Type to be converted
        Returns:
        result StackMapType

      • generate_Type_from_StackMapType

        protected final org.apache.bcel.generic.Type generate_Type_from_StackMapType​(org.apache.bcel.classfile.StackMapType smt)
        Convert a StackMapType to a Type.
        Parameters:
        smt - StackMapType to be converted
        Returns:
        result Type

      • getSize

        protected final int getSize​(org.apache.bcel.classfile.StackMapType smt)
        Return the operand size of this type (2 for long and double, 1 otherwise).
        Parameters:
        smt - a StackMapType object
        Returns:
        the operand size of this type

      • update_full_frame_stack_map_entries

        protected final void update_full_frame_stack_map_entries​(int offset,
                                                         org.apache.bcel.generic.Type type_new_var,
                                                         org.apache.bcel.generic.LocalVariableGen[] locals)
        Update any FULL_FRAME StackMap entries to include a new local var. The locals array is a copy of the local variables PRIOR to the addition of the new local in question.
        Parameters:
        offset - offset into stack of the new variable we are adding
        type_new_var - type of new variable we are adding
        locals - a copy of the local variable table prior to this modification

      • add_new_argument

        @Deprecated
protected final org.apache.bcel.generic.LocalVariableGen add_new_argument​(org.apache.bcel.generic.MethodGen mgen,
                                                                          String arg_name,
                                                                          org.apache.bcel.generic.Type arg_type)
        Deprecated.
        use add_new_parameter(org.apache.bcel.generic.MethodGen, java.lang.String, org.apache.bcel.generic.Type)
        Add a new parameter to the method. This will be added after last current parameter and before the first local variable. This might have the side effect of causing us to rewrite the method byte codes to adjust the offsets for the local variables - see below for details.

        Must call fix_local_variable_table (just once per method) before calling this routine.

        Parameters:
        mgen - MethodGen to be modified
        arg_name - name of new parameter
        arg_type - type of new parameter
        Returns:
        a LocalVariableGen for the new parameter

      • add_new_parameter

        protected final org.apache.bcel.generic.LocalVariableGen add_new_parameter​(org.apache.bcel.generic.MethodGen mgen,
                                                                           String arg_name,
                                                                           org.apache.bcel.generic.Type arg_type)
        Add a new parameter to the method. This will be added after last current parameter and before the first local variable. This might have the side effect of causing us to rewrite the method byte codes to adjust the offsets for the local variables - see below for details.

        Must call fix_local_variable_table (just once per method) before calling this routine.

        Parameters:
        mgen - MethodGen to be modified
        arg_name - name of new parameter
        arg_type - type of new parameter
        Returns:
        a LocalVariableGen for the new parameter

      • create_method_scope_local

        protected final org.apache.bcel.generic.LocalVariableGen create_method_scope_local​(org.apache.bcel.generic.MethodGen mgen,
                                                                                   String local_name,
                                                                                   org.apache.bcel.generic.Type local_type)
        Create a new local with a scope of the full method. This means we need to search the existing locals to find the proper index for our new local. This might have the side effect of causing us to rewrite the method byte codes to adjust the offsets for the existing local variables - see below for details.

        Must call fix_local_variable_table (just once per method) before calling this routine.

        Parameters:
        mgen - MethodGen to be modified
        local_name - name of new local
        local_type - type of new local
        Returns:
        a LocalVariableGen for the new local

      • fix_local_variable_table

        @EnsuresNonNull("initial_type_list")
protected final void fix_local_variable_table​(org.apache.bcel.generic.MethodGen mgen)
        Under some circumstances, there may be problems with the local variable table. These problems occur when the Java compiler adds unnamed entries. There may be unnamed parameters and/or unnamed local variables. These items appear as gaps in the LocalVariable table. This routine creates LocalVariable entries for these missing items.
        1. The java Compiler allocates a hidden parameter for the constructor of an inner class. These items are given the name $hidden$ appended with their offset.
        2. The Java compiler allocates unnamed local temps for:
          • saving the exception in a finally clause
          • the lock for a synchronized block
          • interators
          • (others?)
          These items are given the name DaIkOnTeMp appended with their offset.
        Parameters:
        mgen - MethodGen to be modified

      • bcel_calc_stack_types

        protected final StackTypes bcel_calc_stack_types​(org.apache.bcel.generic.MethodGen mg)
        Calculates the types on the stack for each instruction using the BCEL stack verification routines.
        Parameters:
        mg - MethodGen for the method to be analyzed
        Returns:
        a StackTypes object for the method