[Courgette] Clean up Disassembler; fix ELF Memory leaks.

courgette/disassembler_elf_32_arm.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COURGETTE_DISASSEMBLER_ELF_32_ARM_H_
 #define COURGETTE_DISASSEMBLER_ELF_32_ARM_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
+#include <map>
+
 #include "base/macros.h"
 #include "courgette/disassembler_elf_32.h"
-#include "courgette/memory_allocator.h"
 #include "courgette/types_elf.h"
 
 namespace courgette {
 
 class AssemblyProgram;
 
 enum ARM_RVA {
   ARM_OFF8,
   ARM_OFF11,
   ARM_OFF24,
   ARM_OFF25,
   ARM_OFF21,
 };
 
 class DisassemblerElf32ARM : public DisassemblerElf32 {
  public:
   class TypedRVAARM : public TypedRVA {
    public:
     TypedRVAARM(ARM_RVA type, RVA rva) : TypedRVA(rva), type_(type) { }
 
+    ~TypedRVAARM() override { }
+
+    // TypedRVA interfaces.
+    CheckBool ComputeRelativeTarget(const uint8_t* op_pointer) override;
+    CheckBool EmitInstruction(AssemblyProgram* program,
+                              RVA target_rva) override;
+    uint16_t op_size() const override;
+
     uint16_t c_op() const { return c_op_; }
 
-    virtual CheckBool ComputeRelativeTarget(const uint8_t* op_pointer);
-
-    virtual CheckBool EmitInstruction(AssemblyProgram* program,
-                                      RVA target_rva);
-
-    virtual uint16_t op_size() const;
-
    private:
     ARM_RVA type_;
-
-    uint16_t c_op_;  // set by ComputeRelativeTarget()
+    uint16_t c_op_;  // Set by ComputeRelativeTarget().
     const uint8_t* arm_op_;
   };
 
-  explicit DisassemblerElf32ARM(const void* start, size_t length);
+  DisassemblerElf32ARM(const void* start, size_t length);
 
-  virtual ExecutableType kind() { return EXE_ELF_32_ARM; }
+  ~DisassemblerElf32ARM() override { };
 
-  virtual e_machine_values ElfEM() { return EM_ARM; }
+  // DisassemblerElf32 interfaces.
+  ExecutableType kind() const override { return EXE_ELF_32_ARM; }
+  e_machine_values ElfEM() const override { return EM_ARM; }
 
+  // Takes an ARM or thumb opcode |arm_op| of specified |type| and located at
+  // |rva|, extracts the instruction-relative target RVA into |*addr| and
+  // encodes the corresponding Courgette opcode as |*c_op|.
+  //
+  // Details on ARM opcodes, and target RVA extraction are taken from
+  // "ARM Architecture Reference Manual", section A4.1.5 and
+  // "Thumb-2 supplement", section 4.6.12.
+  // ARM_OFF24 is for the ARM opcode. The rest are for thumb opcodes.
   static CheckBool Compress(ARM_RVA type,
                             uint32_t arm_op,
                             RVA rva,
                             uint16_t* c_op /* out */,
                             uint32_t* addr /* out */);
 
+  // Inverts the process in Compress() method. Takes Courgette op |c_op| and
+  // relative address |addr| to reconstruct the original ARM or thumb op
+  // |*arm_op|.
   static CheckBool Decompress(ARM_RVA type,
                               uint16_t c_op,
                               uint32_t addr,
                               uint32_t* arm_op /* out */);
 
  protected:
-
-  virtual CheckBool RelToRVA(Elf32_Rel rel, RVA* result)
-    const WARN_UNUSED_RESULT;
-
-  virtual CheckBool ParseRelocationSection(
-      const Elf32_Shdr *section_header,
-        AssemblyProgram* program) WARN_UNUSED_RESULT;
-
-  virtual CheckBool ParseRel32RelocsFromSection(
-      const Elf32_Shdr* section) WARN_UNUSED_RESULT;
+   // DisassemblerElf32 interfaces.
+  CheckBool RelToRVA(Elf32_Rel rel, RVA* result)
+    const WARN_UNUSED_RESULT override;
+  CheckBool ParseRelocationSection(
+      const Elf32_Shdr* section_header,
+      AssemblyProgram* program) WARN_UNUSED_RESULT override;
+  CheckBool ParseRel32RelocsFromSection(
+      const Elf32_Shdr* section) WARN_UNUSED_RESULT override;
 
 #if COURGETTE_HISTOGRAM_TARGETS
   std::map<RVA, int> rel32_target_rvas_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(DisassemblerElf32ARM);
 };
 
 }  // namespace courgette
 
 #endif  // COURGETTE_DISASSEMBLER_ELF_32_ARM_H_