U T T A M G A N D H I S Y N E R Z I P

H T T P : / / W W W . L I N K E D I N . C O M / P U B / U T T A M -G A N D H I / 2 1 / 7 A A / 2 4

Effective C++

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Acknowledgments

�  This presentation is based on Scott Meyers well known book ‘Effective C++’

�  http://www.amazon.com/Effective-Specific-Improve-Programs-Designs/dp/0321334876

Variable Declaration

�  Delay as far as possible ¡  can avoid construction and destruction, ¡  keeps the context in which it is required ¡  for loop construction, consider creating in loop based on cost

of assignment v/s cost of construct destructor

Passing of Parameters

�  Pass by value ¡  Primitive types ¡  STL function objects, iterators

�  Pass by reference ¡  User defined objects

÷ Efficient than pass by value ÷ No slicing

�  Return by reference ¡  Local data should not be returned by reference

const 1/2

�  Replacing #define with const ¡  Reduced object code ¡  Better error message ¡  Control over scope

�  Enum ¡  Can be used instead of const ¡  Cannot take address of enum

�  const_iterator

const 2/2

�  const return type �  const input parameter �  const member function of a class �  const overloading of member functions �  Use of mutable

casts

�  static_cast �  dynamic_cast �  const_cast �  reinterpret_cast

Member initialization list

�  Efficiency ¡  Default constructor plus assignment are replaced by copy

constructor �  Order of declaration in class

¡  Order of initialization list

�  Const and reference member ¡  must be initialized in member initializer list

inlining

�  inlining does in-place replacement of code �  Improves efficiency �  Can lead to increased or decreased code size �  Inlining is a request to compiler �  Certain functions may not be inlined

¡  Called through function pointers ¡  Containing loops ¡  Virtual functions ¡  Constructor and destructor are worst candidates for inlining

Compilation

�  forward declare where possible �  Keep declaration and definition in separate files

¡  Not possible for templates

Non-local static object initialization

�  The order of initialization in different translation units is undefined ¡  Solution-> use function which return static object by reference

Default functions 1/2

�  Default functions ¡  default constructor, ¡  Assignment ¡  copy constructor ¡  destructor ¡  & operator

�  If parameterized constructor is user defined, default constructor will not be provided

�  default copy constructor does bitwise copy �  copy constructor and assignment operator not generated if, there is a ref member or const member

Default functions 2/2

�  To avoid default copy constructor ¡  declare them private and don't define them ¡  Derive from base class with private copy constructor ¡  Use boost::noncopyable

constructor destructor

�  Virtual destructor ¡  Needed for base classes ¡  Compiler will invoke the base destructor only without it

�  Pure virtual destructor ¡  To create abstract classes ¡  Having body in pure virtual destructor will help compiler while

invoking the base class destructor

�  Throwing exception ¡  Destructor should never throw exception

Inheritance 1/4

�  Design ¡  public inheritance

÷ Should always represent is-a relationship ¢  Penguin is not a bird ¢  Square is not a rectangle

Inheritance 2/4

�  Design ¡  Inheritance of interface v/s inheritance of implementation. ¡  public inheritance = inheritance of interfaces ¡  Pure virtual functions = inheritance of interface ¡  impure virtual functions = inheritance of interface plus

inheritance of a default implementation. ¡  Non-virtual functions = inheritance of interface plus

inheritance of a mandatory implementation.

Inheritance 3/4

�  Private inheritance (is implemented in terms of ) ¡  When only implementation is required ¡  e.g. class adapter pattern

�  Names in derived classes hide names in base classes �  To make them visible

¡  Using declaration ¡  Forwarding function

�  don't redefine non-virtual inherited function

Inheritance 4/4

�  Multiple inheritance complexities ¡  lead to ambiguity issues ¡  May need virtual inheritance. ¡  Virtual inheritance costs

÷ size, speed, and complexity of initialization and assignment. ¡  It's practical when base classes have no data. ¡  Some practical uses

÷ public inheritance for an Interface and private inheritance for implementation

Composition

�  has-a relationship ¡  e.g. car has wheels ¡  Aggregation v/s composition

÷  In C++ a class having pointer members is composition whereas class having concrete members is aggregation

÷ Aggregation has full control of aggregated object ÷ Composition can share the contained object with other classes

Virtual Function

�  Don’t call virtual function from constructor or destructor ¡  Derived part is not yet constructed when in base class

constructor �  Never redefine an inherited default parameter value

¡  default parameter values are statically bound, ¡  virtual functions are dynamically bound.

Operator overloading

�  Assignment operator should return reference to *this ¡  To support a = b = c ( chaining )

�  Check for self-copy in assignment operator ¡  If copying is deleting the existing object first, the object may

delete itself

Copy constructor

�  copy constructor should call base copy constructor

RAII

�  Use constructor and destructor for resource management

�  Use std::shared_ptr or std::scoped_ptr instead of raw pointers

�  Use std::vector instead of arrays �  std::shared_ptr, with function object as argument

for action other than delete

Misc

�  new[] delete[] should be matched �  Namespace usage

¡  package extensibility ¡  better encapsulation ¡  precise control over what to include

Designing Interfaces

�  Simple to use correctly and hard to misuse ¡  Consistency with built-in types

÷ a = b = c ¡  Restriction on types ¡  Constraining object values

÷ Date, Calendar ¡  Eliminating client side resource management