Bjarne Stroustrup's C++ Style and Technique FAQ

Modified December 17, 2011

These are questions about C++ Style and Technique that people ask me often.
If you have better questions or comments on the answers,
feel free to email me (bs@research.att.com).
Please remember that I can't spend all of my time improving my homepages.

For more general questions, see my
general FAQ.

For terminology and concepts, see my
C++ glossary.

Please note that these are just a collection of questions and answers. They are not
a substitute for a carefully selected sequence of examples and explanations
as you would find in a good textbook. Nor do they offer detailed and precise
specifications as you would find in a reference manual or the standard.
See
The Design and Evolution of C++ for questions
related to the design of C++.
See The C++ Programming Language for questions
about the use of C++ and its standard library.

Translations:

• Chinese
  of some of this Q&A with annotations
• another Chinese version.
• Japanese
• Ukrainian

• Topics:
  • Getting started
  • Classes
  • Hierarchy
  • Templates and generic programming
  • Memory
  • Exceptions
  • Other language features
  • Trivia and style
• Getting started:
  • How do I write this very simple program?
  • Can you recommend a coding standard?
  • How do I read a string from input?
  • How do I convert an integer to a string?
• Classes:
  • How are C++ objects laid out in memory?
  • Why is "this" not a reference?
  • Why is the size of an empty class not zero?
  • How do I define an in-class constant?
  • Why isn't the destructor called at the end of scope?
  • Does "friend" violate encapsulation?
  • Why doesn't my constructor work right?
• Class hierarchies:
  • Why do my compiles take so long?
  • Why do I have to put the data in my class declarations?
  • Why are member functions not virtual by default?
  • Why don't we have virtual constructors?
  • Why are destructors not virtual by default?
  • What is a pure virtual function?
  • Why doesn't C++ have a final keyword?
  • Can I call a virtual function from a constructor?
  • Can I stop people deriving from my class?
  • Why doesn't C++ have a universal class Object?
  • Do we really need multiple inheritance?
  • Why doesn't overloading work for derived classes?
  • Can I use "new" just as in Java?
• Templates and generic programming:
  • Why can't I define constraints for my template parameters?
  • Why can't I assign a vector<Apple> to a vector<Fruit>?
  • Is "generics" what templates should have been?
  • why use sort() when we have "good old qsort()"?
  • What is a function object?
  • What is an auto_ptr and why isn't there an auto_array?
  • Why doesn't C++ provide heterogenous containers?
  • Why are the standard containers so slow?
• Memory:
  • How do I deal with memory leaks?
  • Why doesn't C++ have an equivalent to realloc()?
  • What is the difference between new and malloc()?
  • Can I mix C-style and C++ style allocation and deallocation?
  • Why must I use a cast to convert from void*?
  • Is there a "placement delete"?
  • Why doesn't delete zero out its operand?
  • What's wrong with arrays?
• Exceptions:
  • Why use exceptions?
  • How do I use exceptions?
  • Why can't I resume after catching an exception?
  • Why doesn't C++ provide a "finally" construct?
  • Can I throw an exception from a constructor? From a destructor?
  • What shouldn't I use exceptions for?
• Other language features:
  • Can I write "void main()"?
  • Why can't I overload dot, ::, sizeof, etc.?
  • Can I define my own operators?
  • How do I call a C function from C++?
  • How do I call a C++ function from C?
  • Why does C++ have both pointers and references?
  • Should I use NULL or 0?
  • What's the value of i++ + i++?
  • Why are some things left undefined in C++?
  • What good is static_cast?
  • So, what's wrong with using macros?
• Trivia and style:
  • How do you pronounce "cout"?
  • How do you pronounce "char"?
  • Is ``int* p;'' right or is ``int *p;'' right?
  • Which layout style is best for my code?
  • How do you name variables? Do you recommend "Hungarian"?
  • Should I use call-by-value or call-by-reference?
  • Should I put "const" before or after the type?