Fixed Unused Parameter warning in compiler headers.

src/google/protobuf/compiler/cpp/cpp_field.h

@@ -77,7 +77,7 @@ class FieldGenerator {
   // Generate static default variable for this field. These are placed inside
   // the message class. Most field types don't need this, so the default
   // implementation is empty.
-  virtual void GenerateStaticMembers(io::Printer* printer) const {}
+  virtual void GenerateStaticMembers(io::Printer* /*printer*/) const {}
 
   // Generate prototypes for all of the accessor functions related to this
   // field.  These are placed inside the class definition.
@@ -92,7 +92,7 @@ class FieldGenerator {
   // placed somewhere in the .cc file.
   // Most field types don't need this, so the default implementation is empty.
   virtual void GenerateNonInlineAccessorDefinitions(
-    io::Printer* printer) const {}
+    io::Printer* /*printer*/) const {}
 
   // Generate lines of code (statements, not declarations) which clear the
   // field.  This is used to define the clear_$name$() method as well as
@@ -122,14 +122,15 @@ class FieldGenerator {
   // Generate any code that needs to go in the class's SharedDtor() method,
   // invoked by the destructor.
   // Most field types don't need this, so the default implementation is empty.
-  virtual void GenerateDestructorCode(io::Printer* printer) const {}
+  virtual void GenerateDestructorCode(io::Printer* /*printer*/) const {}
 
   // Generate code that allocates the fields's default instance.
-  virtual void GenerateDefaultInstanceAllocator(io::Printer* printer) const {}
+  virtual void GenerateDefaultInstanceAllocator(io::Printer* /*printer*/)
+      const {}
 
   // Generate code that should be run when ShutdownProtobufLibrary() is called,
   // to delete all dynamically-allocated objects.
-  virtual void GenerateShutdownCode(io::Printer* printer) const {}
+  virtual void GenerateShutdownCode(io::Printer* /*printer*/) const {}
 
   // Generate lines to decode this field, which will be placed inside the
   // message's MergeFromCodedStream() method.