C++ FAQ / Section 4 / FAQ 4.42

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Revised Jul 4, 2012

[4.42] What updates were made for the 07/00 release?

Global changes:

• Moved the main FAQ site to www.parashift.com/c++-faq/. (This was unfortunately necessary due to a business issue involving AT&T and the previous web hosting company, Cerf-Net.)

12 New FAQs:

• [4.42] What updates were made for the 07/00 release?
  (created)
• [11.13] Should my destructor throw an exception when it detects a problem?
  (created)
• [15.9] But shouldn't I always use a printOn() method rather than a friend function?
  (created)
• [16.26] Can I use a garbage collector in C++?
  (created thanks to Hans Boehm)
• [16.27] What are the two kinds of garbage collectors for C++?
  (created thanks to Hans Boehm)
• [16.28] Where can I get more info on garbage collectors for C++?
  (created)
• [17.1] What are some ways try / catch / throw can improve software quality?
  (created)
• [17.9] How can I handle a destructor that fails?
  (created)
• [21.9] Perhaps Ellipse should inherit from Circle then?
  (created)
• [34.1] Why should I use container classes rather than simple arrays?
  (created with help from Stan Brown)
• [39.1] How do I convert a value (a number, for example) to a std::string?
  (created thanks to Rob Stewart)
• [39.2] How do I convert a std::string to a number?
  (created thanks to Rob Stewart)

72 Changed FAQs:

• [2.6] Where can I find the C++ FAQ translated into Chinese?
  (updated the URL)
• [3.1] Is there a C++ FAQ Book in addition to this on-line C++ FAQ?
  (added BookPool.com and AllDirect.com thanks to Stan Brown, plus reorganized)
• [3.2] Is there a big difference between this on-line C++ FAQ and the C++ FAQ Book?
  (changed 'much' to 'many' thanks to Stan Brown)
• [6.6] Who uses C++?
  (rewrote)
• [6.9] Are virtual functions (dynamic binding) central to OO/C++?
  (inserted "the" before "difference" thanks to Stan Brown and reworded references to STL)
• [6.12] Is C++ standardized? Updated!
  (changed "has been finalized" to "was finalized" thanks to Stan Brown)
• [6.13] Where can I get a copy of the ANSI/ISO C++ standard?
  (added URLs to free copies of CD2)
• [9.5] Why should I use inline functions instead of plain old #define macros?
  (rewrote the sentence on #define being evil)
• [10.5] Which constructor gets called when I create an array of Fred objects?
  (changed so it uses new-style headers and the std:: syntax and reworded references to STL)
• [10.8] What is the "Named Constructor Idiom"?
  (fixed a typo (Fred vs. Point) in the prose thanks to Roy LeCates)
• [12.3] OK, OK, already; I'll handle self-assignment. How do I do it?
  (reworded the last paragraph)
• [13.3] What are some examples of operator overloading?
  (changed so it uses the std:: syntax)
• [13.6] Can I overload operator== so it lets me compare two char[] using a string comparison?
  (changed so it uses the std:: syntax)
• [13.10] How do I create a subscript operator for a Matrix class?
  (changed so it uses new-style headers and the std:: syntax)
• [13.13] Should I design my classes from the outside (interfaces first) or from the inside (data first)?
  (changed so it uses new-style headers and the std:: syntax and reworded references to STL)
• [15.1] Why should I use <iostream> instead of the traditional <cstdio>?
  (renamed "subclassable" to "inheritable" and revamped to use new-style headers)
• [15.2] Why does my program go into an infinite loop when someone enters an invalid input character?
  (changed so it uses new-style headers and the std:: syntax)
• [15.4] How does that funky while (std::cin >> foo) syntax work?
  (changed so it uses new-style headers and the std:: syntax)
• [15.5] Why does my input seem to process past the end of file?
  (changed so it uses new-style headers and the std:: syntax)
• [15.6] Why is my program ignoring my input request after the first iteration?
  (changed so it uses new-style headers and the std:: syntax)
• [15.8] How can I provide printing for my class Fred?
  (changed so it uses new-style headers and the std:: syntax)
• [15.10] How can I provide input for my class Fred?
  (changed so it uses new-style headers and the std:: syntax)
• [15.11] How can I provide printing for an entire hierarchy of classes?
  (changed so it uses new-style headers and the std:: syntax)
• [15.13] How can I "reopen" std::cin and std::cout in binary mode?
  (changed so it uses new-style headers and the std:: syntax)
• [15.16] Why can't I open a file in a different directory such as "..\test.dat"?
  (changed so it uses new-style headers and uses the std:: syntax)
• [16.6] Do I need to check for NULL after p = new Fred()?
  (changed so it uses new-style headers and the std:: syntax)
• [16.7] How can I convince my (older) compiler to automatically check new to see if it returns NULL?
  (changed the example to use throw rather than abort() thanks to Stan Brown; changed to use new-style headers and the std:: syntax)
• [16.14] After p = new Fred[n], how does the compiler know there are n objects to be destructed during delete[] p?
  (changed "popluar" to "popular" thanks to Fabrice Clerc)
• [16.16] How do I allocate multidimensional arrays using new?
  (fixed a leak in the third manipulateArray() by moving another for loop into the try block)
• [16.17] But the previous FAQ's code is SOOOO tricky and error prone! Isn't there a simpler way?
  (clarified the last paragraph)
• [16.18] But the above Matrix class is specific to Fred! Isn't there a way to make it generic?
  (rewrote)
• [16.20] Does C++ have arrays whose length can be specified at run-time?
  (changed so it uses new-style headers and the std:: syntax and reworded references to STL)
• [16.23] How do I provide reference counting with copy-on-write semantics?
  (rewrote the first paragraph for clarity thanks to Fabrice Clerc)
• [16.24] How do I provide reference counting with copy-on-write semantics for a hierarchy of classes?
  (changed so it uses new-style headers and the std:: syntax)
• [17.11] How do I change the string-length of an array of char to prevent memory leaks even if/when someone throws an exception?
  (rewrote the last half)
• [18.1] What is "const correctness"?
  (changed so it uses new-style headers and the std:: syntax)
• [18.2] How is "const correctness" related to ordinary type safety?
  (changed so it uses new-style headers and the std:: syntax)
• [18.10] What is a "const member function"?
  (removed a spurious ")" thanks to Stan Brown)
• [18.15] Why does the compiler allow me to change an int after I've pointed at it with a int const*?
  (changed so it uses new-style headers and the std:: syntax)
• [19.3] How do you express inheritance in C++?
  (added "derived class of" to the list of synonyms)
• [19.7] How can I protect derived classes from breaking when I change the internal parts of the base class?
  (renamed "subclass" to "derived class")
• [21.4] Is an array of Derived a kind-of array of Base?
  (changed so it uses new-style headers and the std:: syntax and reworded references to STL)
• [21.5] Does array-of-Derived is-not-a-kind-of array-of-Base mean arrays are bad?
  (changed so it uses new-style headers and the std:: syntax and reworded references to STL)
• [22.3] What is an ABC?
  (renamed "subclass" to "derived class")
• [22.4] What is a "pure virtual" member function?
  (renamed "subclass" to "derived class")
• [24.3] Which should I prefer: composition or private inheritance?
  (changed so it uses new-style headers and the std:: syntax)
• [24.5] How is protected inheritance related to private inheritance?
  (renamed "subclass" to "derived class")
• [24.6] What are the access rules with private and protected inheritance?
  (renamed "subclass" to "derived class")
• [27.4] What's the difference between <xxx> and <xxx.h> headers?
  (changed <xyz.h> to <xxx.h> and wordsmithed thanks to Stan Brown)
• [27.6] Is the ?: operator evil since it can be used to create unreadable code?
  (changed so it uses new-style headers and the std:: syntax)
• [27.10] Are there any lint-like guidelines for C++?
  (changed so it uses new-style headers and the std:: syntax)
• [27.12] Which is better: identifier names that_look_like_this or identifier names thatLookLikeThis?
  (improved the precision and added the last two paragraphs thanks to Chris Hurst)
• [27.13] Are there any other sources of coding standards?
  (fixed some URLs thanks to James S. Adelman and Stan Brown)
• [29.16] Why is floating point so inaccurate? Why doesn't this print 0.43?
  (changed so it uses new-style headers and the std:: syntax)
• [30.4] How do you use inheritance in C++, and is that different from Smalltalk?
  (renamed "subclass" to "derived class")
• [30.5] What are the practical consequences of differences in Smalltalk/C++ inheritance?
  (renamed "subclass" to "derived class")
• [31.3] What's the difference between virtual data and dynamic data?
  (renamed "subclass" to "derived class")
• [31.8] Does the poor performance of reference semantics mean I should pass-by-value?
  (renamed "subclass" to "derived class")
• [34.2] How can I make a perl-like associative array in C++?
  (changed so it uses new-style headers and the std:: syntax)
• [34.5] How can I insert/access/change elements from a linked list/hashtable/etc?
  (reworded, plus changed so it uses new-style headers and the std:: syntax)
• [35.2] What's the syntax / semantics for a "class template"?
  (changed so it uses new-style headers and the std:: syntax)
• [35.3] What's the syntax / semantics for a "function template"?
  (changed so it uses new-style headers and the std:: syntax)
• [37.1] What is the "STL"?
  (changed so it uses new-style headers and the std:: syntax)
• [37.2] Where can I get a copy of "STL"?
  (added URLs for the SGI implementation and STLport thanks to Stan Brown)
• [37.3] How can I find a Fred object in an STL container of Fred* such as std::vector<Fred*>?
  (changed so it uses new-style headers and the std:: syntax)
• [38.5] Where can I get information about the C++ compiler from {Borland, IBM, Microsoft, Sun, etc.}?
  (updated the URL for IBM VisualAge C++ thanks to Rick Alther; updated the URL for GNU C++ thanks to Martin Honnen)
• [39.4] What should be done with macros that contain if?
  (added the last three paragraphs, including the link showing why we don't use do {...} while (false))
• [39.5] What should be done with macros that have multiple lines?
  (changed "if (1)..." to "if (true)..." and "do...while (0)" to "do...while (false)")
• [39.8] What are the C++ scoping rules for for loops?
  (because the scoping rules for for loops are no longer "new" (thanks Stan Brown), rewote the FAQ)
• [39.14] Why can't I put a forward-declared class in a std::vector<>?
  (changed so it uses new-style headers and the std:: syntax)
• [40.3] Are there any pretty-printers that reformat C++ source code?
  (added HPS Beauty)
• [40.6] Why does my DOS C++ program says "Sorry: floating point code not linked"?
  (added a cross reference and updated to new header syntax)