[4] Recent changes to this document  Updated! 
(Part of C++ FAQ Lite, Copyright © 1991-2005, Marshall Cline, cline@parashift.com)

FAQs in section [4]:

• [4.1] What updates were made for the 06/05 release?  New! 
• [4.2] What updates were made for the 05/05 release?  New! 
• [4.3] What updates were made for the 04/05 release?
• [4.4] What updates were made for the 03/05 release?
• [4.5] What updates were made for the 02/05 release?
• [4.6] What updates were made for the 12/04 release?
• [4.7] What updates were made for the 06/04 release?
• [4.8] What updates were made for the 08/03 release?
• [4.9] What updates were made for the 06/03 release?
• [4.10] What updates were made for the 05/03 release?
• [4.11] What updates were made for the 04/03 release?
• [4.12] What updates were made for the 03/03 release?
• [4.13] What updates were made for the 02/03 release?
• [4.14] What updates were made for the 01/03 release?
• [4.15] What updates were made for the 12/02 release?
• [4.16] What updates were made for the 09/02 release?
• [4.17] What updates were made for the 06/02 release?
• [4.18] What updates were made for the 05/02 release?
• [4.19] What updates were made for the 04/02 release?
• [4.20] What updates were made for the 03/02 release?
• [4.21] What updates were made for the 08/01 release?
• [4.22] What updates were made for the 04/01 release?
• [4.23] What updates were made for the 07/00 release?
• [4.24] What updates were made for the 03/00 release?
• [4.25] What updates were made for the 01/00 release?
• [4.26] What updates were made for the 10/99 release?
• [4.27] What updates were made for the 07/99 release?
• [4.28] What updates were made for the 06/98 release?
• [4.29] What updates were made for the 05/98 release?
• [4.30] What updates were made for the 09/97 release?
• [4.31] What updates were made for the 01/97 release?
• [4.32] What updates were made for the 11/96 release?
• [4.33] What updates were made for the 10/96 release?
• [4.34] What updates were made for the 09/96 release?
• [4.35] What updates were made for the 08/96 release?
• [4.36] What updates were made for the 07/96 release?
• [4.37] What updates were made for the 06/96 release?
• [4.38] What updates were made for the 05/96 release?
• [4.39] What updates were made for the 04/96 release?
• [4.40] What updates were made for the 03/96 release?
• [4.41] What updates were made for the 09/95 release?
• [4.42] What updates were made for the 06/95 release?
• [4.43] What updates were made for the 04/95 release?
• [4.44] What updates were made for the 03/95 release?
• [4.45] What updates were made for the 01/95 release?
• [4.46] What updates were made for the 12/94 release?
• [4.47] What updates were made for the 11/94 release?
• [4.48] What updates were made for the 08/94 release?
• [4.49] What updates were made before 08/94?

2 New FAQs:

• [4.1] What updates were made for the 06/05 release?
• [27.5] Should I use using namespace std in my code?
  (thanks to a suggestion from Victor Bazarov)

6 Changed FAQs:

• [6.3] What's the big deal with OO?
  (fixed a typo thanks to Allan W)
• [6.16] Will I sometimes use any so-called "evil" constructs?
  (improved the tooltip ("bubble help-text") that pops up on "milquetoast")
• [6.18] What should I tell people who complain that the word "FAQ" is misleading, that it emphasizes the questions rather than the answers, and that we should all start using a different acronym?
  (corrected a misspelling)
• [8.6] When should I use references, and when should I use pointers?
  (expounded on "sentinel reference" thanks to Vangelis Katsikaros)
• [10.6] Should my constructors use "initialization lists" or "assignment"?
  (fixed a typo thanks to Vangelis Katsikaros)
• [18.9] What does "Fred const* x" mean?
  (added a paragraph about making sure nobody confuses Fred const* x and Fred* const x)

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Generic changes:

• Reworked the lists of mirror sites and translations on the opening page.

4 New FAQs:

• [2.3] Where can I find the C++ FAQ Lite translated into Bosnian / Serbian / Croation?
  (with much thanks to translator Zaharije Pasalic)
• [4.2] What updates were made for the 05/05 release?
• [13.12] I still don't get it. Why shouldn't my Matrix class's interface look like an array-of-array?
• [25.15] What is the exact order of destructors in a multiple and/or virtual inheritance situation?
  (thanks to a question from Noam)

4 Changed FAQs:

• [13.10] How do I create a subscript operator for a Matrix class?
  (added a pointer to the FAQ containing the rationale)
• [13.11] Why shouldn't my Matrix class's interface look like an array-of-array?
  (added an indication that the outer operator[] can return a (shudder) raw pointer to the zeroth element of the corresponding row)
• [35.13] Can the previous problem hurt me silently? Is it possible that the compiler will silently generate the wrong code?
  (fixed a typo thanks to Assaf Lavie)
• [38.5] Where can I get information about the C++ compiler from {Borland, IBM, Microsoft, Sun, etc.}?
  (updated the link to Microsoft Visual C++ thanks to Amos Shapira)

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5 New FAQs:

• [4.3] What updates were made for the 04/05 release?
• [6.4] What's the big deal with generic programming?
  (thanks to a suggestion from Ioannis Vranos)
• [6.18] What should I tell people who complain that the word "FAQ" is misleading, that it emphasizes the questions rather than the answers, and that we should all start using a different acronym?
• [17.13] I have too many try blocks; what can I do about it?
  (thanks to a question from Gustavo A. Baratto)
• [29.20] What other "newbie" guides are there for me?
  (thanks to Alf Steinbach for putting together The Correct C++ Tutorial)

18 Changed FAQs:

• [5.1] What does IMHO mean? (or IMO, IMNSHO, FWIW, OTOH, etc.)?
  (added the Acronym Finder thanks to Jarno Lamberg)
• [6.2] Is C++ a perfect language?
  (made it clear that "warts" are common to all languages and tools)
• [6.3] What's the big deal with OO?
  (rewrote third paragraph to reflect the reality that "as a better C" is sometimes intentional)
• [6.7] How long does it take to learn OO/C++?
  (wordsmithed)
• [6.9] Are virtual functions (dynamic binding) central to OO/C++?
  (added the last paragraph to clarify relationship between virtual functions and generic programming)
• [8.7] What is a handle to an object? Is it a pointer? Is it a reference? Is it a pointer-to-a-pointer? What is it?
  (slight wordsmithing thanks to Steve Fábián)
• [16.22] How do I do simple reference counting?
  (fixed a subtle bug in the assignment operator thanks to Gianni Mariani)
• [16.23] How do I provide reference counting with copy-on-write semantics?
  (fixed a subtle bug in the assignment operator thanks to Gianni Mariani)
• [16.24] How do I provide reference counting with copy-on-write semantics for a hierarchy of classes?
  (fixed a subtle bug in the assignment operator thanks to Gianni Mariani)
• [17.10] How do I throw polymorphically?
  (fixed a typo thanks to Lyle Ziegelmiller)
• [23.4] Okay, but is there a way to simulate that behavior as if dynamic binding worked on the this object within my base class's constructor?
  (clarified that this is called the "Dynamic Binding During Initialization Idiom")
• [23.5] I'm getting the same mess with destructors: calling a virtual on my this object from my base class's destructor ends up ignoring the override in the derived class; what's going on?
  (fixed the cross-references thanks to Alf Steinbach and Michal Bartoszkiewicz)
• [27.13] Are there any other sources of coding standards?
  (added www.codingstandard.com/ thanks to Robert Buckley)
• [29.5] What are the criteria for choosing between short / int / long data types?
  (added the disclaimer that <stdint.h> is not guaranteed to include int32_t thanks to Padmanabhan V. Karthic)
• [29.15] What is this NaN thing?
  (added recommendation to use isnan() where available thanks to Stefan Ring)
• [35.12] Why am I getting errors when my template-derived-class accesses something it inherited from its template-base-class?
  (fixed a typo thanks to Neil Falwasser; while I was in there I rewrote most of it)
• [35.13] Can the previous problem hurt me silently? Is it possible that the compiler will silently generate the wrong code?
  (added a cross-reference and did some wordsmithing)
• [39.13] What special considerations are needed when forward declarations are used with inline functions?
  (added the inline-below-Barney workaround thanks to Ganesh Sundaram, plus the nested-classes workaround; rewrote the "workarounds" paragraph)

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9 New FAQs:

• [2.6] Where can I find the C++ FAQ Lite translated into Greek?
  (with much thanks to translator Vangelis Katsikaros)
• [2.10] Where can I find the C++ FAQ Lite translated into Turkish?
  (with much thanks to translator Doruk Caner)
• [4.4] What updates were made for the 03/05 release?
• [16.2] Is it safe to delete the same pointer twice?
  (promted by a question from Hans Van den Eynden)
• [18.11] What's the relationship between a return-by-reference and a const member function?
• [18.12] What's the deal with "const-overloading"?
• [20.4] What happens in the hardware when I call a virtual function? How many layers of indirection are there? How much overhead is there?
• [20.5] How can a member function in my derived class call the same function from its base class?
• [23.5] I'm getting the same mess with destructors: calling a virtual on my this object from my base class's destructor ends up ignoring the override in the derived class; what's going on?

23 Changed FAQs:

• [5.9] Which newsgroup should I post my questions?
  (added microsoft.public.dotnet.languages.vc thanks to Ioannis Vranos)
• [5.10] Should I post job advertisements and/or resumés on comp.lang.c++?
  (duplicated the attribution that was in the recent changes section thanks to Daryle Walker)
• [5.11] What if I really need a job; should I post my resumé on comp.lang.c++?
  (duplicated the attribution that was in the recent changes section thanks to Daryle Walker)
• [6.13] Where can I get a copy of the ANSI/ISO C++ standard?
  (updated the Barnes & Noble URL)
• [10.5] Which constructor gets called when I create an array of Fred objects?
  (added the paragraph on placement-new thanks to Alf P. Steinbach; rewrote the other examples)
• [10.6] Should my constructors use "initialization lists" or "assignment"?
  (added "non-static reference" to the list of data members that must appear within an initialization list thanks to Daryle Walker)
• [10.13] How do I prevent the "static initialization order fiasco"?
  (changed *.hpp to *.h)
• [10.14] Why doesn't the construct-on-first-use idiom use a static object instead of a static pointer?
  (changed *.hpp to *.h)
• [10.15] How do I prevent the "static initialization order fiasco" for my static data members?
  (changed *.hpp to *.h)
• [12.1] What is "self assignment"?
  (changed *.hpp to *.h)
• [16.18] But the above Matrix class is specific to Fred! Isn't there a way to make it generic?
  (changed *.hpp to *.h)
• [19.8] I've been told to never use protected data, and instead to always use private data with protected access functions. Is that a good rule?
  (added the goal of providing a coherent/opaque interface to the goals of data hiding thanks to Yechiel Kimchi )
• [23.1] Is it okay for a non-virtual function of the base class to call a virtual function?
  (changed *.hpp to *.h)
• [23.7] What's the meaning of, Warning: Derived::f(char) hides Base::f(double)?
  (added the paragraph on "hiding happens when you have a derived-pointer, not when you have a base-pointer" thanks to Daniel Kabs)
• [26.6] I'm sooooo confused. Would you please go over the rules about bytes, chars, and characters one more time?
  (fixed a spelling error thanks to Daryle Walker)
• [26.10] Can I define an operator overload that works with built-in / intrinsic / primitive types?
  (added "or enumeration type" to the first sentence thanks to Daryle Walker)
• [29.19] If an enumeration type is distinct from any other type, what good is it? What can you do with it?
  (added the caveat on the last line of code thanks to Daryle Walker)
• [32.1] What do I need to know when mixing C and C++ code?
  (added a caveat about some of the requirements depending on your compiler-vendor thanks to Mitchell Charity)
• [34.3] Is the storage for a std::vector<T> guaranteed to be contiguous?
  (changed &v[0] to v.empty() ? NULL : &v[0] thanks to David Hilsee)
• [35.9] How can I avoid linker errors with my template classes?
  (fixed a bug by changing template Foo<int> to template class Foo<int> thanks to alert readers Eric Gorr and Patrick Guio)
• [37.9] Where can I get tons and tons of more information on C++ class libraries?
  (fixed the URL to www.mathtools.net/C_C__ thanks to Daryle Walker)
• [39.7] Why can't the compiler find my header file in #include "c:\test.h" ?
  (changed *.hpp to *.h)
• [40.3] Are there any pretty-printers that reformat C++ source code?
  (fixed the URL to C++2LaTeX thanks to Daryle Walker and Nicolás Conde)

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Generic changes:

• Split the section on Containers and Templates into a section on Containers and a section on Templates.

6 New FAQs:

• [4.5] What updates were made for the 02/05 release?
• [9.9] With inline member functions that are defined outside the class, is it best to put the inline keyword next to the declaration within the class body, next to the definition outside the class body, or both?
• [10.9] Does return-by-value mean extra copies and extra overhead?
• [13.8] Okay, that tells me the operators I can override; which operators should I override?
  (thanks to Conrad Weisert for suggesting the topic)
• [13.9] What are some guidelines / "rules of thumb" for overloading operators?
• [33.11] Can you make functionoids faster than normal function calls?
  (thanks to a suggestion from Padmanabhan V. Karthic)

23 Changed FAQs:

• [5.9] Which newsgroup should I post my questions?
  (added a link to TechiWarehouse thanks to Adam Fisher)
• [9.3] Do inline functions improve performance?
  (added two bullets on cache misses thanks to a suggestion from Tom Brown)
• [10.6] Should my constructors use "initialization lists" or "assignment"?
  (added an "or when" and a cross reference to the last paragraph, plus fixed some grammar, thanks to Padmanabhan V. Karthic)
• [10.8] What is the "Named Constructor Idiom"?
  (added the last paragraph to discuss the return-by-value optimization thanks to a question from Can Isin)
• [10.18] What is the "Named Parameter Idiom"?
  (changed friend File; to friend class File; thanks to Mehri and Padmanabhan V. Karthic)
• [10.19] Why am I getting an error after declaring a Foo object via Foo x(Bar())?
  (added the alternate syntax Foo x = Bar(); thanks to a suggestion from Mike Dunn)
• [13.13] Should I design my classes from the outside (interfaces first) or from the inside (data first)?
  (changed friend LinkedList; to friend class LinkedList;, and similarly with LinkedListIterator, thanks to Padmanabhan V. Karthic)
• [16.19] What's another way to build a Matrix template?
  (added some pros/cons (mostly pros) thanks to a suggestion from Padmanabhan V. Karthic)
• [16.22] How do I do simple reference counting?
  (changed friend FredPtr; to friend class FredPtr; thanks to Padmanabhan V. Karthic)
• [16.24] How do I provide reference counting with copy-on-write semantics for a hierarchy of classes?
  (changed friend Fred; to friend class Fred; thanks to Padmanabhan V. Karthic)
• [17.7] What should I catch?
  (fixed a grammatical error thanks to Padmanabhan V. Karthic)
• [17.12] Exception handling seems to make my life more difficult; clearly I'm not the problem, am I??
  (rewrote the last bullet thanks to a critique of the old wording from Jan Ploski)
• [18.15] Why does the compiler allow me to change an int after I've pointed at it with a const int*?
  (initialized variable x in main() thanks to Yechiel Kimchi )
• [27.13] Are there any other sources of coding standards?
  (hoisted the Sutter/Alexandrescu book out to its proper, primary place; also added (thanks to Kevlin Henney) links to and insights about Elemtel and Industrial Strength C++)
• [29.5] What are the criteria for choosing between short / int / long data types?
  (added the disclaimer that <stdint.h> is not part of the C++ standard and might not be supplied by your compiler vendor thanks to Padmanabhan V. Karthic)
• [29.18] What is the type of an enumeration such as enum Color? Is it of type int?
  (fixed a typo thanks to Surendra Phadke and Brandon Forehand)
• [30.5] What are the practical consequences of differences in Smalltalk/C++ inheritance?
  (fixed the spelling of Maserati thanks to Alessandro/Gruppo Visione)
• [33.2] How do I pass a pointer-to-member-function to a signal handler, X event callback, system call that starts a thread/task, etc?
  (fixed a grammatical error thanks to Padmanabhan V. Karthic)
• [33.5] How can I avoid syntax errors when calling a member function using a pointer-to-member-function?
  (added return value (int ans = ...) to make the sample-code more illustrative thanks to Pete Brunet)
• [33.10] What the heck is a functionoid, and why would I use one?
  (added a virtual dtor thanks to Marcus; added parameters to doit() thanks to Dirk Bonekaemper; made the dtor pure virtual as an optimization)
• [35.12] Why am I getting errors when my template-derived-class accesses something it inherited from its template-base-class?
  (added public: thanks to Alexander Kamotsky and Leonard "SoulSkorpion" Frankel and Stefan Näwe; fixed a grammatical error thanks to Val Kartchner)
• [39.4] What should be done with macros that contain if?
  (clarified why we use the (void)0 part thanks to a suggestion from Padmanabhan V. Karthic)
• [40.1] How can I generate HTML documentation for my classes? Does C++ have anything similar to javadoc?
  (updated the link to www.robertnz.net/cpp_site.html#Documentation thanks to Robert Davies and Peter Kammer)

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Generic changes:

• In an attempt to stem the inexorable tide of spam, I've obfuscated the email address of anyone who's contributed to the FAQ. The email addresses are easy to decode, e.g., (NOSPAM)marshall(DASH)cline(AT)parashift(DOT)com becomes marshall-cline@parashift.com, though hopefully the spam-bots won't bother (yea right).

3 New FAQs:

• [4.6] What updates were made for the 12/04 release?
• [10.19] Why am I getting an error after declaring a Foo object via Foo x(Bar())?
  (thanks to James Kanze)
• [17.12] Exception handling seems to make my life more difficult; clearly I'm not the problem, am I??
  (thanks to an email conversation with Bob Bell)

9 Changed FAQs:

• [2.2] What happened to the one-click-download option?
  (added request to stop emailing me requests to send it manually)
• [5.2] How do I get other people to do my homework problem for me?
  (duplicated the "Jack Klein" attribution that was in the recent changes section thanks to Daryle Walker)
• [6.5] Is C++ better than Ada? (or Visual Basic, C, FORTRAN, Pascal, Smalltalk, or any other language?)
  (fixed a spelling error thanks to Gerriet Backer)
• [21.8] But I have a Ph.D. in Mathematics, and I'm sure a Circle is a kind of an Ellipse! Does this mean Marshall Cline is stupid? Or that C++ is stupid? Or that OO is stupid?
  (added the paragraph on constant Ellipses thanks to Luke Palmer)
• [23.7] What's the meaning of, Warning: Derived::f(char) hides Base::f(double)?
  (included a new example, changed the parameter types so the behavior seems more bizarre/ominous, and added a note about warnings not being standardized, thanks to Daniel Kabs)
• [25.3] So there are times when multiple inheritance isn't bad?!??
  (fixed a typo thanks to Sumit Rajan)
• [27.1] What are some good C++ coding standards?
  (added last few sentences on the Sutter/Alexandrescu book)
• [27.13] Are there any other sources of coding standards?
  (added a bullet on the Sutter/Alexandrescu book)
• [28.4] Should I buy one book, or several?
  (added last few sentences recommending purchase of a coding-standards book)

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Polish translation:

• The Polish translation of the C++ FAQ is now available thanks to the hard work of translators Tomek Bywalec, Bartek Krzemien and Janek Pustelnik. The translation isn't finished, but the translators deserve congratulations and thanks for what they've done so far.

16 New FAQs:

• [2.7] Where can I find the C++ FAQ Lite translated into Polish?
  (with much thanks to translators Tomek Bywalec, Bartek Krzemien and Janek Pustelnik)
• [4.7] What updates were made for the 06/04 release?
• [6.17] Is it important to know the technical definition of "good OO"? Of "good class design"?
• [17.6] What should I throw?
  (thanks to Carl Daniel)
• [17.7] What should I catch?
  (thanks to Carl Daniel)
• [17.8] But MFC seems to encourage the use of catch-by-pointer; should I do the same?
  (thanks to Carl Daniel)
• [17.9] What does throw; (without an exception object after the throw keyword) mean? Where would I use it?
  (thanks to Carl Daniel)
• [17.10] How do I throw polymorphically?
  (thanks to Carl Daniel)
• [17.11] When I throw this object, how many times will it be copied?
  (thanks to Carl Daniel)
• [33.9] I need something like function-pointers, but with more flexibility and/or thread-safety; is there another way?
• [33.10] What the heck is a functionoid, and why would I use one?
  (thanks to a question from Christian Cuvier)
• [35.11] How can any human hope to understand these overly verbose template-based error messages?
  (thanks to gentle pestering from Leor Zolman)
• [35.12] Why am I getting errors when my template-derived-class accesses something it inherited from its template-base-class?
  (thanks to Daveed Vandevoorde)
• [35.13] Can the previous problem hurt me silently? Is it possible that the compiler will silently generate the wrong code?
  (thanks to Daveed Vandevoorde)
• [39.15] Why do some people think x = ++y + y++ is bad?
• [39.16] What's the deal with "sequence points"?

32 Changed FAQs:

• [2.4] Where can I find the C++ FAQ Lite translated into Chinese?
  (updated the URL for the GB-encoded translation thanks to Imron Alston)
• [6.5] Is C++ better than Ada? (or Visual Basic, C, FORTRAN, Pascal, Smalltalk, or any other language?)
  (added to the last paragraph to make it stronger(!!))
• [6.13] Where can I get a copy of the ANSI/ISO C++ standard?
  (rewrote from scratch, thanks to comments and corrections from Petter Häggholm, Lars Christensen, Pieter Van Dyck and Jim Fischer)
• [6.15] What does the FAQ mean by "such and such is evil"?
  (changed "such-in-such" to "such and such" thanks to Darren Frith and Simon OLeary)
• [8.4] What does object.method1().method2() mean?
  (removed a couple superfluous ")"s)
• [10.3] Can one constructor of a class call another constructor of the same class to initialize the this object?
  (added a strong statement against using placement new in this situation thanks to questions from Marc Page and Steve Peters)
• [10.6] Should my constructors use "initialization lists" or "assignment"?
  (fixed a (subtle!) miswording in the second paragraph thanks to Tomek Bywalec, Bartek Krzemien and Tian Yu; added the stuff on exceptions (see last paragraph) thanks to Alf Steinbach)
• [10.18] What is the "Named Parameter Idiom"?
  (added a bunch more example code and clarified the explanation of class OpenFile thanks to Tomek Bywalec and Bartek Krzemien)
• [12.1] What is "self assignment"?
  (fixed an error in the code-comments thanks to Jonathan Mcdougall)
• [13.10] How do I create a subscript operator for a Matrix class?
  (fixed a typo thanks to Doug Schwartz)
• [15.1] Why should I use <iostream> instead of the traditional <cstdio>?
  (removed a superfluous ")")
• [15.9] But shouldn't I always use a printOn() method rather than a friend function?
  (removed a superfluous ")")
• [15.17] How can I tell {if a key, which key} was pressed before the user presses the ENTER key?
  (updated the URL thanks to Sampath Patnala)
• [15.18] How can I make it so keys pressed by users are not echoed on the screen?
  (fixed the title thanks to Todd Catelotti)
• [16.6] Do I need to check for NULL after p = new Fred()?
  (added a caveat for MSVC++ thanks to Graham Knap)
• [20.8] What is a "virtual constructor"?
  (rewrote the last paragraph for clarity)
• [21.2] Converting Derived* → Base* works OK; why doesn't Derived** → Base** work?
  (fixed a grammatical error thanks to Philip S Tellis)
• [22.5] How do you define a copy constructor or assignment operator for a class that contains a pointer to a (abstract) base class?
  (added a "contract" to the Fred ctor thanks to Bo Majewski; changed the return types in the derived classes to exploit covariant return types thanks to Dan Raviv)
• [23.9] How can I set up my class so it won't be inherited from?
  (fixed a bug in the friend declaration, renamed the classes to Fred and FredBase, and general wordsmithing)
• [28.7] What are some best-of-breed C++ programming-by-example guides?
  (added details about Musser and Saini thanks to Randy Sherman)
• [29.5] What are the criteria for choosing between short / int / long data types?
  (added stuff about <stdint.h> thanks to Oliver Kellogg)
• [29.18] What is the type of an enumeration such as enum Color? Is it of type int?
  (added the caveat about converting only valid integers to enumerations thanks to Mike Radford)
• [33.2] How do I pass a pointer-to-member-function to a signal handler, X event callback, system call that starts a thread/task, etc?
  (added caveat about using extern "C" non-member function thanks to Rolf Magnus)
• [33.4] Why am I having trouble taking the address of a C++ function?
  (rewrote the opening paragraph to give a better explanation of the "short answer")
• [35.8] How can I avoid linker errors with my template functions?
  (added a note about the export keyword thanks to Greg Comeau)
• [35.9] How can I avoid linker errors with my template classes?
  (added a note about the export keyword thanks to Greg Comeau)
• [35.10] Why do I get linker errors when I use template friends?
  (added the required <> within the friend declaration thanks to Christophe Barbe; added the "define it within the class body" approach thanks to Frode Angell-Petersen AKA Sprudling)
• [36.10] How do I serialize objects that contain pointers to other objects, but those pointers form a tree with no cycles and only "trivial" joins?
  (fixed some spelling errors thanks to Steve Fallows)
• [38.13] Is it possible to convert C++ to C?
  (added LLVM thanks to Chris Sabre)
• [39.4] What should be done with macros that contain if?
  (modified the primary solution to include (void)0, and thanks to Erik Haugen and Mike Morearty, added some pros/cons commentary to the secondary solution; plus did some general wordsmithing)
• [39.5] What should be done with macros that have multiple lines?
  (modified the primary solution to include (void)0, and thanks to Erik Haugen and Mike Morearty, added some pros/cons commentary to the secondary solution; plus did some general wordsmithing)
• [39.7] Why can't the compiler find my header file in #include "c:\test.h" ?
  (softened the wording to reflect the difference between header-names and string-literals thanks to Michiel Salters)

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1 New FAQs:

• [4.8] What updates were made for the 08/03 release?

10 Changed FAQs:

• [2.2] What happened to the one-click-download option?
  (disabled due to spam)
• [6.16] Will I sometimes use any so-called "evil" constructs?
  (changed "effect" to "affect" thanks to J.K. Lowden)
• [10.3] Can one constructor of a class call another constructor of the same class to initialize the this object?
  (fixed typo thanks to Charles Daniels)
• [13.10] How do I create a subscript operator for a Matrix class?
  (fixed a memory leak thanks to Paladin)
• [16.18] But the above Matrix class is specific to Fred! Isn't there a way to make it generic?
  (plugged a memory leak in the ctor)
• [16.22] How do I do simple reference counting?
  (fixed a typo thanks to Lee Graham)
• [29.5] What are the criteria for choosing between short / int / long data types?
  (changed "at least 2 bytes" to "at least 16 bits" (and fixed other similar bone-headed mistakes) thanks to Peter Nilsson)
• [36.11] How do I serialize objects that contain pointers to other objects, and those pointers form a graph that might have cycles or non-trivial joins?
  (fixed a spelling error)
• [39.3] Can I templatize the above functions so they work with other types?
  (fixed a bug (type_info<T>::name() → typeid(x).name()) thanks to Thomas Tutone)
• [39.8] What are the C++ scoping rules for for loops?
  (fixed typo thanks to Henrik Torkelund)

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2 New FAQs:

• [4.9] What updates were made for the 06/03 release?
• [35.10] Why do I get linker errors when I use template friends?
  (with lots of input from Carl Daniel)

13 Changed FAQs:

• [5.1] What does IMHO mean? (or IMO, IMNSHO, FWIW, OTOH, etc.)?
  (added HAND, YHBT and YHL)
• [10.12] What's the "static initialization order fiasco"?
  (wordsmithed)
• [16.18] But the above Matrix class is specific to Fred! Isn't there a way to make it generic?
  (changed class to typename in template declarations)
• [16.19] What's another way to build a Matrix template?
  (changed class to typename in template declarations)
• [32.8] How can I pass an object of a C++ class to/from a C function?
  (added the last two paragraphs)
• [35.2] What's the syntax / semantics for a "class template"?
  (changed class to typename in template declarations)
• [35.3] What's the syntax / semantics for a "function template"?
  (changed class to typename in template declarations)
• [35.4] How do I explicitly select which version of a function template should get called?
  (changed class to typename in template declarations)
• [35.7] Why can't I separate the definition of my templates class from it's declaration and put it inside a .cpp file?
  (changed class to typename in template declarations)
• [35.8] How can I avoid linker errors with my template functions?
  (changed class to typename in template declarations)
• [35.9] How can I avoid linker errors with my template classes?
  (changed class to typename in template declarations)
• [37.3] How can I find a Fred object in an STL container of Fred* such as std::vector<Fred*>?
  (changed class to typename in template declarations)
• [39.3] Can I templatize the above functions so they work with other types?
  (changed class to typename in template declarations)

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1 New FAQs:

• [4.10] What updates were made for the 05/03 release?

5 Changed FAQs:

• [9.4] How can inline functions help with the tradeoff of safety vs. speed?
  (fixed a misspelling)
• [16.17] But the previous FAQ's code is SOOOO tricky and error prone! Isn't there a simpler way?
  (fixed a memory leak in the ctor when nrows or ncols was zero thanks to Chris Carton)
• [16.24] How do I provide reference counting with copy-on-write semantics for a hierarchy of classes?
  (fixed a subtle bug in the code thanks to James Megquier)
• [25.12] What special considerations do I need to know about when I inherit from a class that uses virtual inheritance?
  (fixed spelling error ("becuase") thanks to Olga Colombo)
• [37.4] Where can I get help on how to use STL?
  (added SGI's STL Programmer's guide)

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1 New FAQs:

• [4.11] What updates were made for the 04/03 release?

13 Changed FAQs:

• [3.1] Is there a C++ FAQ Book in addition to the C++ FAQ Lite?
  (rewrote, added several bookstores, and updated the URL for the source code)
• [7.5] How does C++ help with the tradeoff of safety vs. usability?
  (clarified that it is data declared as static at file-scope that is deprecated)
• [9.3] Do inline functions improve performance?
  (rewrote the "can cause thrashing" bullet thanks to Zarius Tularial; also reworded throughout to strengthen the points)
• [16.19] What's another way to build a Matrix template?
  (added methods nrows() and ncols() thanks to Christopher Mackie and Paolo Copello; inserted std:: in front of vector a few times thanks to Francisco Osorio G)
• [20.8] What is a "virtual constructor"?
  (added a note that MS VC++ 7.0 handles covariant return types thanks to Paolo Copello)
• [23.9] How can I set up my class so it won't be inherited from?
  (added the paragraph that the virtual inheritance approach might increase sizeof(Leaf))
• [26.6] I'm sooooo confused. Would you please go over the rules about bytes, chars, and characters one more time?
  (reworded the fifth bullet (so it doesn't use "effect") thanks to Mal Morrow and Chuck Pahlmeyer)
• [26.7] What is a "POD type"?
  (fixed a misspelling (equialent → equivalent) thanks to Mal Morrow)
• [34.3] Is the storage for a std::vector<T> guaranteed to be contiguous?
  (fixed a couple of typos in the last two paragraphs thanks to Dean Stanton)
• [37.2] Where can I get a copy of "STL"?
  (fixed the URL for the SGI implementation thanks to Jeremy Bishop)
• [38.2] Where can I get more information on using MFC and Visual C++?
  (rewrote with updated URLs thanks to Paolo Copello)
• [39.8] What are the C++ scoping rules for for loops?
  (replaced the pithy one-liner at the very beginning and corrected another typo thanks to Mans Gunnarsson)
• [40.3] Are there any pretty-printers that reformat C++ source code?
  (fixed the URL for C++2LaTeX thanks to Vinay Kumar Nallamothu)

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1 New FAQs:

• [4.12] What updates were made for the 03/03 release?

4 Changed FAQs:

• [5.9] Which newsgroup should I post my questions?
  (clarified that "the C++ language" means the language defined by the ISO/ANSI C++ Standard thanks to Victor Bazarov)
• [18.8] What does "Fred const& x" mean?
  (rewrote to make it even clearer that this is a business decision, and that the outcome will be different in different organizations)
• [18.9] What does "Fred const* x" mean?
  (rewrote to make it even clearer that this is a business decision, and that the outcome will be different in different organizations)
• [25.6] Is there a simple way to visualize all these tradeoffs?
  (fixed a typo ("calss" → "class") thanks to John Ericson)

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4 New FAQs:

• [4.13] What updates were made for the 02/03 release?
• [25.8] What is the "dreaded diamond"?
  (thanks to Carl Daniel)
• [25.9] Where in a hierarchy should I use virtual inheritance?
  (thanks to Carl Daniel)
• [25.10] What does it mean to "delegate to a sister class" via virtual inheritance?
  (thanks to Carl Daniel)

12 Changed FAQs:

• [5.1] What does IMHO mean? (or IMO, IMNSHO, FWIW, OTOH, etc.)?
  (added PEBCAC and PEBCAK thanks to William L. Thomson Jr.)
• [6.15] What does the FAQ mean by "such and such is evil"?
  (fixed a typo in second to last paragraph thanks to Joe Sewell)
• [15.3] How can I get std::cin to skip invalid input characters?
  (changed ignore()'s first parameter from int to std::streamsize thanks to Mike Wahler)
• [15.6] Why is my program ignoring my input request after the first iteration?
  (changed ignore()'s first parameter from int to std::streamsize thanks to Mike Wahler)
• [17.2] How can I handle a constructor that fails?
  (rewrote to make a stronger case against "zombie" objects)
• [18.17] Why am I getting an error converting a Foo** → const Foo**?
  (fixed a bug in the code (*q vs. *p) thanks to Richard van Wegen)
• [19.9] Okay, so exactly how should I decide whether to build a "protected interface"?
  (fixed a couple of typos thanks to Joe Sewell)
• [23.7] What's the meaning of, Warning: Derived::f(char) hides Base::f(double)?
  (added the last paragraph thanks to Carl Daniel)
• [23.9] How can I set up my class so it won't be inherited from?
  (added the virtual base class technique thanks to Carl Daniel)
• [25.11] What special considerations do I need to know about when I use virtual inheritance?
  (updated thanks to Carl Daniel)
• [25.12] What special considerations do I need to know about when I inherit from a class that uses virtual inheritance?
  (updated thanks to Carl Daniel)
• [33.2] How do I pass a pointer-to-member-function to a signal handler, X event callback, system call that starts a thread/task, etc?
  (fixed a typo in the name "The X Window System" thanks to Maurizio Colucci)

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9 New FAQs:

• [4.14] What updates were made for the 01/03 release?
• [15.3] How can I get std::cin to skip invalid input characters?
  (thanks to Mike Wahler and Sam Dutton)
• [18.9] What does "Fred const* x" mean?
• [18.17] Why am I getting an error converting a Foo** → const Foo**?
  (thanks to a question from Stephen Tashiro)
• [34.3] Is the storage for a std::vector<T> guaranteed to be contiguous?
  (thanks to Daveed Vandevoorde)
• [36.3] How do I decide whether to serialize to human-readable ("text") or non-human-readable ("binary") format?
• [36.4] How serialize/unserialize simple types like numbers, characters, strings, etc.?
• [36.5] How exactly do I read/write simple types in human-readable ("text") format?
• [36.6] How exactly do I read/write simple types in non-human-readable ("binary") format?
  (fixed a typo (indent vs. intent) and added a few clarifications thanks to Troy S)

16 Changed FAQs:

• [1.5] Trademarks
  (added comment about non-commercial sites being exempt from trademark dilution laws)
• [2.1] Where's the closest mirror site to access this document?
  (added URL to the mirror site in Israel thanks to Yechiel Kimchi )
• [6.16] Will I sometimes use any so-called "evil" constructs?
  (added "'Think' is not a four-letter word" thanks to Dave Power)
• [13.14] How can I overload the prefix and postfix forms of operators ++ and --?
  (fixed typo in title thanks to Kevin Goodsell)
• [18.8] What does "Fred const& x" mean?
  (added the paragraph starting "Note: you'll have to overcome a certain amount of inertia...")
• [21.2] Converting Derived* → Base* works OK; why doesn't Derived** → Base** work?
  (wordsmithed and clarified)
• [21.6] Is a Circle a kind-of an Ellipse?
  (strengthened the wording)
• [21.7] Are there other options to the "Circle is/isnot kind-of Ellipse" dilemma?
  (strengthened the wording)
• [21.8] But I have a Ph.D. in Mathematics, and I'm sure a Circle is a kind of an Ellipse! Does this mean Marshall Cline is stupid? Or that C++ is stupid? Or that OO is stupid?
  (strengthened the wording)
• [29.17] Why doesn't my floating-point comparison work?
  (clarified the code)
• [33.2] How do I pass a pointer-to-member-function to a signal handler, X event callback, system call that starts a thread/task, etc?
  (rewrote to discuss the (typical) void* parameter on many system- and GUI-calls thanks to Ryan Melville)
• [36.2] How do I select the best serialization technique?
  (fixed a misspelling ("forth" vs. "fourth") thanks to Charles Brockman; rewrote to include cross-references to the text/binary decision and how to handle simple types)
• [36.7] How do I serialize objects that aren't part of an inheritance hierarchy and that don't contain pointers to other objects?
  (added description of sample algorithm thanks to Niall Douglas; rewrote everything else as well)
• [38.5] Where can I get information about the C++ compiler from {Borland, IBM, Microsoft, Sun, etc.}?
  (updated several links thanks to Thomas Tutone)
• [40.1] How can I generate HTML documentation for my classes? Does C++ have anything similar to javadoc?
  (added the link to PERCEPS)
• [40.3] Are there any pretty-printers that reformat C++ source code?
  (updated the URL for Source Styler)

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Big-picture changes:

• Added a new section on Multiple and Virtual Inheritance.
• Added a new section on Serialization.
• Added  New!  and  Updated!  tags on the section titles.

34 New FAQs:

• [4.15] What updates were made for the 12/02 release?
• [13.14] How can I overload the prefix and postfix forms of operators ++ and --?
  (thanks to Sandeep Grover)
• [13.15] Which is more efficient: i++ or ++i?
• [15.12] How can I open a stream in binary mode?
  (thanks to Simon Barner)
• [15.14] How can I write/read objects of my class to/from a data file?
• [15.15] How can I send objects of my class to another computer (e.g., via a socket, TCP/IP, FTP, email, a wireless link, etc.)?
• [19.8] I've been told to never use protected data, and instead to always use private data with protected access functions. Is that a good rule?
  (thanks to a question from Andrew Chan)
• [19.9] Okay, so exactly how should I decide whether to build a "protected interface"?
• [21.11] How could "it depend"??!? Aren't terms like "Circle" and "Ellipse" defined mathematically?
• [25.1] How is this section organized?
• [25.2] I've been told that I should never use multiple inheritance. Is that right?
• [25.3] So there are times when multiple inheritance isn't bad?!??
• [25.4] What are some disciplines for using multiple inheritance?
• [25.5] Can you provide an example that demonstrates the above guidelines?
• [25.6] Is there a simple way to visualize all these tradeoffs?
• [25.7] Can you give another example to illustrate the above disciplines?
• [25.11] What special considerations do I need to know about when I use virtual inheritance?
• [25.12] What special considerations do I need to know about when I inherit from a class that uses virtual inheritance?
• [25.13] What special considerations do I need to know about when I use a class that uses virtual inheritance?
• [25.14] One more time: what is the exact order of constructors in a multiple and/or virtual inheritance situation?
  (thanks to Carl Daniel)
• [33.7] Can I convert a pointer-to-member-function to a void*?
• [33.8] Can I convert a pointer-to-function to a void*?
• [35.8] How can I avoid linker errors with my template functions?
  (thanks to a suggestion by Michael Kochetkov)
• [35.9] How can I avoid linker errors with my template classes?
  (thanks to a suggestion by Michael Kochetkov)
• [36.1] What's this "serialization" thing all about?
  (thanks to a question from Stephen Tashiro)
• [36.2] How do I select the best serialization technique?
• [36.7] How do I serialize objects that aren't part of an inheritance hierarchy and that don't contain pointers to other objects?
• [36.8] How do I serialize objects that are part of an inheritance hierarchy and that don't contain pointers to other objects?
• [36.9] How do I serialize objects that contain pointers to other objects, but those pointers form a tree with no cycles and no joins?
• [36.10] How do I serialize objects that contain pointers to other objects, but those pointers form a tree with no cycles and only "trivial" joins?
• [36.11] How do I serialize objects that contain pointers to other objects, and those pointers form a graph that might have cycles or non-trivial joins?
  (thanks to a question from Stephen Tashiro)
• [36.12] Are there any caveats when serializing / unserializing objects?
• [36.13] What's all this about graphs, trees, nodes, cycles, joins, and joins at the leaves vs. internal nodes?
• [39.3] Can I templatize the above functions so they work with other types?
  (inspired by Merlyn Morgan-Graham)

20 Changed FAQs:

• [5.2] How do I get other people to do my homework problem for me?
  (added the "serious bodily harm" quote thanks to Jack Klein)
• [5.4] How can I find out about general netiquette so I don't embarrass myself?
  (added the joke/quote about top-posting)
• [6.15] What does the FAQ mean by "such and such is evil"?
  (fixed a typo in the last paragraph thanks to YaoJun)
• [10.16] Do I need to worry about the "static initialization order fiasco" for variables of built-in/intrinsic types?
  (added std:: prefix on cout thanks to