Questions tagged [c++]

C++ is a general-purpose programming language. Initially, it was designed as an extension to C and has a similar syntax, but it is now a completely different language. Use this tag for questions about code (to be) compiled with a C++ compiler. Use a version-specific tag for questions related to a specific standard revision [C++11], [C++14], [C++17], [C++20], [C++23], or [C++26], etc.

What is C++?

C++ is a (mostly) statically-typed, free-form, (usually) compiled, multi-paradigm, intermediate-level general-purpose programming language; not to be confused with C or C++/CLI. It was developed in the early 1980s by Bjarne Stroustrup, initially as a set of extensions to the C programming language. Building on C, C++ improved type-safety and added support for automatic resource management, object orientation, generic programming, and exception handling, among other features.

New to C++?

Whether you are new to programming or coming to C++ from another programming language, it is highly recommended to have a good book from which to learn the language. We keep a detailed list of books.

If you are looking for good compilers, GCC is the most commonly used compiler on Linux and other Unix-like platforms; Clang is the official compiler on Mac and FreeBSD; Microsoft Visual C++ is the most commonly used compiler on Windows. The Intel® C++ Compiler is also commonly used for its optimized numerical computations on Windows, Linux, and Mac.

Turbo-C++ 3.0 is from 1991, extremely outdated, and not recommended. See the previous paragraph for free choices from this millennium.

Join us in chat, where we discuss C++, programming in general, and even other stuff when the sun goes down and boredom creeps in. Don't forget your sense of humor, but keep it civilized.

Tag usage

When posting questions about C++ programming, please make sure to include:

  • Target system and compiler information. This includes the compiler name, version, and settings used to compile.
  • If your question is specific to one particular version of the language, add , , , or . Questions about boost should add the tag . Details about the different versions can be found further below in this wiki.
  • Unless the question explicitly mentions which version of the C++ standard is used, it is assumed that the current version is used. That is, whichever version of ISO 14882 ISO currently lists as active. Please have this in mind when answering or commenting on questions tagged .

Using and together

C and C++ are two distinct and often incompatible languages. Avoid using both tags in the same question unless you have good reasons.

A question should be tagged with only, if:

  • It contains pure C, with no trace of C++, or questions with code that could be either language.
  • The code is compiled with a C compiler.

A question should be tagged with only, if:

  • It contains code with any C++ features. Even though the code may be "C style".
  • The code is compiled with a C++ compiler.

A question should be tagged with both and if it is about:

  • Specific differences between C and C++.
  • Compatibility or porting code between C and C++.
  • C++ code that uses C libraries (for example code using extern "C").

Editing and moderation guidelines for posts with both and tags:

To edit/re-tag/moderate questions with both tags, it is recommended that you have full edit privileges and either a gold or a gold badge.

If you encounter a post with both tags, edit/re-tag it if needed according to the above rules. If you can tell the language by reading the posted code, simply edit tags accordingly. Avoid prompting the user "is it C or C++?" in comments unless the question is truly unclear.

One example of an unclear question is when the user explicitly claims that they are programming in C, but posts code or compiler messages for C++. If so, prompt for clarification and close vote as unclear.

"Either C or C++ is fine" opinions from the OP are a strong indication of a poor or unclear question. Answers may be very different depending on the language picked. Prompt for clarification, close as unclear/too broad until the OP has clarified this.

Be careful about re-tagging questions once there are answers posted, particularly if there are already both C and C++ answers posted. In such cases, the tags should be left alone, since changing them would make posted answers invalid.

Answers with C++ code to a C question that has never been tagged should be deleted as off-topic. Please check the question edit history before flagging/deleting such answers, to verify that the question never had the C++ tag.


In 1998, the C++ standards committee published the first international standard for C++ ISO/IEC 14882:1998, which would be informally known as C++98.


In 2003, the C++ Committee responded to multiple problems that were reported with and revised it accordingly. The changed language was dubbed C++03.


The language standard remained pretty much the same for a long time, but in 2011 a new standard, C++11 (formerly known as C++0x) was published in ISO/IEC 14882:2011. Rather than in a "big bang" approach, it is being rolled out gradually as compilers are supporting the new language features. See Bjarne Stroustrup's C++11 FAQ to see what is new in the language, and check your own compiler's FAQ to see which of those features are currently supported:

A few features that had been under discussion for C++11 have been deferred to the next iteration.


C++14 is a small extension of C++11. It was approved in August 2014 and released in December of the same year. Previously referred to as C++1y the year of approval was uncertain. Many popular compilers already have some level of C++14 support.


C++17 adds a few more major features (and several minor ones). It is usually referred to as C++1z or C++17, as technical work on the new standard was completed in March of 2017. The draft standard was approved (unanimously) by the ISO in September 2017 and officially published in December 2017.


In February 2020 the C++ Standard committee completed work on C++20. It was unanimously approved later that year and got officially published in December 2020.

The following (and more) new features have already been accepted into the C++20:


The following (and more) new features have already been accepted into the C++23 draft:


The following (and more) new features have already been accepted into the C++26 draft:

Online compilers

If you want to give C++ a spin, you can try one of the following online compiler services:

  • Coliru (GCC, Clang)
  • (GCC, Clang)
  • codepad (GCC)
  • rextester (GCC, Clang, Visual C++)
  • (GCC)
  • ELLCC (Clang)
  • CodingGround (GCC)
  • C++Shell (GCC)
  • Wandbox (GCC, Clang)
  • Compiler Explorer (GCC, Clang, ICC, Visual C++). Many versions of GCC/Clang for x86, and also for some non-x86 architectures (ARM, ARM64, PPC, and AVR), as well as the latest versions of Microsoft Visual C++. Beside execution (./a.out button), it includes nicely formatted assembler output, even optionally color-highlighting source and assembler lines to help find which source line maps to which assembler line.
  • C++ Insights (Clang) Trans-compiler of code that shows the C++98 code that maps on modern constructs
  • Quick bench (GCC, Clang) Micro benchmarking tool intended to quickly and simply compare the performances of code snippets.

Stack Overflow's C++ FAQ

External FAQs

Other External Resources

Chat Rooms

798869 questions
12 answers

How can I solve the error LNK2019: unresolved external symbol - function?

I get this error, but I don't know how to fix it. I'm using Visual Studio 2013. I made the solution name MyProjectTest This is the structure of my test solution: -function.h #ifndef MY_FUNCTION_H #define MY_FUNCTION_H int multiple(int x, int…
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Why do we need argc while there is always a null at the end of argv?

It seems that the argv[argc] is always NULL, so I think we can traverse the argument list without argc. A single while loop will do this. If there is always a NULL at the end of argv, why do we need an argc?
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6 answers

How is std::function implemented?

According to the sources I have found, a lambda expression is essentially implemented by the compiler creating a class with overloaded function call operator and the referenced variables as members. This suggests that the size of lambda expressions…
10 answers

How to Use CCache with CMake?

I would like to do the following: If CCache is present in PATH, use "ccache g++" for compilation, else use g++. I tried writing a small my-cmake script containing CC="ccache gcc" CXX="ccache g++" cmake $* but it does not seem to work (running…
amit kumar
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9 answers

How far can memory leaks go?

I've run into memory leaks many times. Usually when I'm malloc-ing like there's no tomorrow, or dangling FILE *s like dirty laundry. I generally assume (read: hope desperately) that all memory is cleaned up at least when the program terminates. Are…
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Are Exceptions in C++ really slow

I was watching Systematic Error Handling in C++—Andrei Alexandrescu he claims that Exceptions in C++ are very very slow. Is this still true for C++98?
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3 answers

What is a subnormal floating point number?

The isnormal() reference page says: Determines if the given floating point number arg is normal, i.e. is neither zero, subnormal, infinite, nor NaN. It's clear what a number being zero, infinite or NaN means. But it also says subnormal. When is a…
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4 answers

What is the difference between "Include Directories" and "Additional Include Directories"

In configuration properties of my project, under the "VC++ directories" there is an entry for "Include Directories". But under "C/C++" option, there is another entry called "Additional Include Directories". Same thing happens with library…
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What is the difference between std::array and std::vector? When do you use one over other?

What is the difference between std::array and std::vector? When do you use one over other? I have always used and considered std:vector as an C++ way of using C arrays, so what is the difference?
Alok Save
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4 answers

Is cout synchronized/thread-safe?

In general I assume that streams are not synchronized, it is up to the user to do appropriate locking. However, do things like cout get special treatment in the standard library? That is, if multiple threads are writing to cout can they corrupt the…
edA-qa mort-ora-y
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What is a niebloid?

With C++20 we can read the term "niebloid" more often now in the cppreference. On SO we can find today 2020/07/16 2 articles mentioning it: First post Second post, talking about customization point objects Google does also not spit out that many…
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C++: What is the size of an object of an empty class?

I was wondering what could be the size of an object of an empty class. It surely could not be 0 bytes since it should be possible to reference and point to it like any other object. But, how big is such an object? I used this small program: #include…
Ashwin Nanjappa
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2 answers

Why is shared_ptr legal, while unique_ptr is ill-formed?

The question really fits in the title: I am curious to know what is the technical reason for this difference, but also the rationale ? std::shared_ptr sharedToVoid; // legal; std::unique_ptr uniqueToVoid; // ill-formed;
Ad N
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9 answers

What does "int& foo()" mean in C++?

While reading this explanation on lvalues and rvalues, these lines of code stuck out to me: int& foo(); foo() = 42; // OK, foo() is an lvalue I tried it in g++, but the compiler says "undefined reference to foo()". If I add int foo() { return…
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Erasing elements from a vector

I want to clear a element from a vector using the erase method. But the problem here is that the element is not guaranteed to occur only once in the vector. It may be present multiple times and I need to clear all of them. My code is something like…
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