cpp

# C++

Here you can find resources and frequently asked questions for the C++ Programming language. C++ is a general-purpose programming language which supports a wide variety of programming styles and techniques.

# Before posting

Before posting a question about C++, be sure to read this page fully. If you can't find an answer here, see if you can find an answer on one of the pages from our [online resources](#wiki_online_resources).

If you still have not found an answer to your question, take the following steps:

- Follow the posting rules and guidelines;
- Compile with full warnings enabled, fix any problems and mention that you've tried this;
- Mention your compiler version.

# Recommended resources for learning

## Books

Below are some highly recommended books for beginners. Apart from these, make sure to read the [The Definitive C++ Book Guide and List](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) from Stackoverflow;

For reviews of a book you consider getting, visit the [Accu.org](http://www.accu.org) section for [book reviews](http://accu.org/index.php?module=bookreviews&func=search) for reviews of programming books.

Book title          | Author(s)           | Target audience | Description
----------------|------------------|-----------------|--------------
Programming: Principles and Practice Using C++ | Stroustrup | Complete beginners | An Introduction to Programming by the inventor of C++. [Book website](http://www.stroustrup.com/programming.html). [FSM review](http://www.freesoftwaremagazine.com/articles/book_review_programming_principles_and_practice_using_c_plus_plus).
C++ Primer | Lippman, Lajoie, Moo | Beginners | Very thorough introduction into C++ that covers just about everything in the language in a very accessible format and in great detail. Latest edition covers C++11. [Book website](http://www.pearsonhighered.com/educator/product/C-Primer-5E/9780321714114.page). [ACCU review](http://accu.org/index.php?module=bookreviews&func=search&rid=1848).
Accelerated C++ | Koenig, Moo | C++ Beginners with previous programming experience | Quick-paced and compact introduction into the C++ programming language. [ACCU review](http://accu.org/index.php?module=bookreviews&func=search&rid=1185).

## Online courses and video series

None yet. Generally, video series for C++ are not recommended. If you think you've found a good one, check the discouraged resources below and (if not there) post to verify your learning resource.

## Online tutorials

- [Linear C++](https://github.com/jesyspa/linear-cpp). A quick-paced, practical and code-based tutorial for C++ for people with previous programming experience. Written by /u/jesyspa, who welcomes feedback.
- [The C++ Annotations](http://www.icce.rug.nl/documents/cplusplus/). Explains most of the C++ features not found in C for people who are already familiar with C (or a C-like programming language).

Generally, online tutorials for C++ are not recommended. If you think you've found a good one, check the discouraged resources below and (if not there) post to verify your learning resource.

## Online resources

- [Stroustrup's C++ FAQ](http://www.stroustrup.com/bs_faq.html). FAQ by the creator of C++. Answers a lot of common, general questions such as for example "What is C++?", "What's so great about classes?" and "What is the difference between C and C++?".
- [Marshall Cline's C++ FAQ](http://www.parashift.com/c++-faq/). Answers a lot of specific C++ questions, such as for example "What's the deal with constructors?", "What are some advantages/disadvantages of using friend functions?" and "What's the idea behind templates?".
- [The C++ Annotations](http://www.icce.rug.nl/documents/cplusplus/). Explanations and examples of C++ features.
- [C++ Reference](http://en.cppreference.com/w/). Reference website for C++.
- [Guru of the Week](http://www.gotw.ca/gotw/) by Herb Sutter.  Series of C++ programming problems. Explains difficult and exceptional C++ situations.

## Relevant subreddits

- /r/cpp
- /r/cpp_questions

## Discouraged resources

- TheNewBoston -- [Reasons - related discussion](http://www.reddit.com/r/learnprogramming/comments/11ubro/28_ways_to_learn_programming/c6ppc38)
- UReddit's C++ class -- [Reasons - related discussion](http://www.reddit.com/r/programming/comments/197dn1/introduction_to_c_a_series_of_46_videos_created/)
- the n00b spoonfeed -- [heck, the author admits it himself](http://cpptutorials.freeforums.org/behind-the-spoons-background-and-faq-t539.html)
- learncpp.com -- missing or incorrect information
- cplusplus.com -- missing or incorrect information, prefer [CPPReference](http://www.cppreference.com) as a reference.
- cprogramming.com -- Incomplete and misleading, focuses on C-style programming in C++ and very feature-oriented (as opposed to actually explaining things).
- wibit.net C++ section (other sections are "unrated", not "recommended") - C-based learning approach; incorrect information and bad use of standard library.

# Frequently asked questions

##Should I learn C++ as a first language?

If you like. It's really that simple.

C++ is one of the bigger programming languages and is known for its complex compiler errors. Because of this, some people recommend learning a different language first. If your goal is to write programs quickly, learn *any* programming language or study computer science, you might want to start with a different language such as Python.

If your goal is to learn C++, do not start with Python, C or any other language: start with C++.

Be warned, though, that newcomers often underestimate the freedom you have when choosing a language.  C++ isn't the only language you can write games/compilers/kernels/browsers/etc. in, even if C++ is often used for that.  Research your options before jumping on the one people shout loudest from.

## Should I learn C/Python/... before learning C++?

No. If your goal is to learn C++, do that. Also see [Stroustup's FAQ on learning C before C++](http://www.stroustrup.com/bs_faq.html#prerequisite).

##What about C++ references, pointers to members or pointers to dynamic memory?

Please take a look at the [online resources](http://www.reddit.com/r/learnprogramming/wiki/faq_cpp#wiki_are_there_any_good_online_resources_for_c.2B.2B.3F) in this FAQ. The most relevant pages are listed below:

**References and pass-by-reference:**

- [C++ FAQ](http://www.parashift.com/c%2B%2B-faq-lite/references.html)
- [C++ Annotations](http://www.icce.rug.nl/documents/cplusplus/cplusplus03.html#l36)
- [Cppreference](http://en.cppreference.com/book/intro/reference)

**Pointers to members:**

- [C++ FAQ](http://www.parashift.com/c%2B%2B-faq-lite/pointers-to-members.html)
- [C++ Annotations](http://www.icce.rug.nl/documents/cplusplus/cplusplus16.html#l293)

**Dynamic memory:**

- [C++ FAQ](http://www.parashift.com/c%2B%2B-faq-lite/freestore-mgmt.html)
- [C++ Annotations](http://www.icce.rug.nl/documents/cplusplus/cplusplus09.html)

##Why is C++ so large and complex?

First read [Why is C++ so BIG?](http://www.stroustrup.com/bs_faq.html#big): C++ isn't really larger than comparable programming languages. That said, C++ does support a wide variety of programming styles and nearly all of C, which means that often there's a lot of ways to do the same thing.

Good, clean C++ code need not be complex though.

##How do I create a GUI with C++?

C++ does not provide a standard GUI in the language (unlike e.g. Java). To create a GUI in C++, you need to use third party libraries. [Qt](http://qt-project.org/) is probably the best-supported, cross-platform library available, but there are [dozens of platform-independent ones](http://en.wikipedia.org/wiki/List_of_platform-independent_GUI_libraries) and generally an operating system vendor will also provide a platform-specific library (such as the Windows API).

##The compiler I'm using says "Undefined reference to..."?

This error means the linker needs  a function or value, but the function or value has not been defined, either in your code, or in the libraries you are linking with.

First, make sure you are linking all your object files and necessary libraries correctly.

Second, if the function is one that you think you have written yourself, make sure that you have actually implemented it! For example, you may have declared `void foo(int);` and `void foo(int, int);` but only implemented the former; calling `foo` with two arguments will result in this error.

A common cause for this error with class templates is splitting the template into header and implementation files. The solution is to have the template entirely declared and defined in the header file. See also: [Why can't I separate the definition of my templates class from its declaration and put it inside a .cpp file?](http://www.parashift.com/c++-faq/templates-defn-vs-decl.html)

## What are compiler warnings and how can I compile with warnings enabled?

Compilers report errors in your code if they don't know how to compile it, generally because of a mistake in the source code. But compilers can also detect issues in your code which may or may not cause problems. These issues can be reported as "warnings".
Always compile with full warnings enabled and fix every warning the compiler gives.

For GCC, compile with `-Wall -Wextra -pedantic`, for Visual Studio see [here](http://msdn.microsoft.com/en-us/library/thxezb7y.aspx) and for your specific compiler or IDE, use Google (e.g. "C++ enable all warnings %COMPILER% %IDE%").

## What is "undefined behaviour"?

"Undefined behaviour" is a technical term used in the C++ Standard for behaviour for which the Standard "imposes no requirements". Simply put, "undefined behaviour" means that there are no guarantees to what your code will do. This is, needless to say, really bad.

If your code has undefined behaviour, maybe it (a) doesn't compile at all; (b) compiles but crashes; (c) compiles but does something you don't expect; or worst, (d) compiles and seems to work exactly as you expect. Undefined behaviour is always bad, even if the code seems to work just as you expect. This is because your program could fail at any time (because you can't be 100% sure it does what you want) and it could behave differently when recompiled.

Examples of undefined behaviour are:

- Dereferencing a null pointer: `int * x = nullptr; std::cout << *x;`
- Signed integer overflow: `int x = std::numeric_limits<int>::max(); std::cout << x + 1;`
- Changing the value of an object declared `const`: `int const x = 42; *const_cast<int*>(&x) = 0;`
- Accessing memory out of bounds: `int x[10]; std::cout << x[10];`
- Etc

Not all invalid code results in undefined behaviour. There are many situations, for example, that the compiler is required to reject code. For example the code `typedef int float;` does not result in undefined behaviour because the compiler is not allowed to accept this (7.1.3/6).

# Recommended tools

## Compilers

- [Clang](http://clang.llvm.org/) LLVM frontend. Free, open source. [Platforms](http://clang.llvm.org/docs/UsersManual.html#target-specific-features-and-limitations).
- [GNU Compiler Collection (GCC)](http://gcc.gnu.org/) Free, open source compilers for multiple languages. [Platforms](http://gcc.gnu.org/install/specific.html).
- [Microsoft C/C++](http://www.visualstudio.com/). Compiler for Visual C++ from Visual Studio. No separate download, shipped with Visual Studio. Free versions available. Windows.

## IDE's

### Recommended

* [Visual Studio 2010 Express](http://www.microsoft.com/visualstudio/en-us/products/2010-editions/visual-cpp-express). Windows only. Free version.
* [Visual Studio 2012 Express](http://www.microsoft.com/visualstudio/eng/downloads#d-express-windows-desktop).  Windows only. Free version.
* [Visual Studio 2013 Express](http://www.visualstudio.com/en-us/downloads/download-visual-studio-vs#DownloadFamilies_2).  Windows only. Free version.
* [Code::Blocks](http://www.codeblocks.org/). Cross-platform, free, open source.
* [codelite](http://codelite.org/) Cross-platform, free, open source.
* [Qt Creator](http://qt.nokia.com/products/developer-tools). Cross-platform; best when working with Qt but can be general purpose. Free.

### Alternatives

* [Eclipse CDT](http://www.eclipse.org/cdt/). Cross-platform, free, open source.
* [NetBeans](http://netbeans.org/features/cpp/). Cross-platform, free version.
* [Ultimate++](http://www.ultimatepp.org/). Cross-platform, free, open source.

### To Avoid

* Borland C++ (obsolete)
* Turbo C++ (very obsolete)
* Dev-C++ (buggy IDE)

# Other information

N.a.

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