How Are The __cplusplus Directive Defined In Various Compilers?

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Introduction

The __cplusplus directive is a preprocessor macro in C++ that provides information about the version of the C++ compiler being used. This macro is defined by the compiler and can be used by programmers to write code that is compatible with different versions of the C++ standard. In this article, we will explore how the __cplusplus directive is defined in various compilers and what it signifies.

What is the __cplusplus Directive?

The __cplusplus directive is a preprocessor macro that is defined by the compiler. It is used to provide information about the version of the C++ compiler being used. The value of this macro is typically a number that represents the version of the C++ standard being used. For example, __cplusplus might be defined as 199711L to indicate that the compiler is using the C++98 standard.

How is the __cplusplus Directive Defined in Various Compilers?

The __cplusplus directive is defined differently in various compilers. Here are some examples:

GCC Compiler

In the GCC compiler, the __cplusplus directive is defined as follows:

  • __cplusplus is defined as 199711L for C++98
  • __cplusplus is defined as 201103L for C++11
  • __cplusplus is defined as 201402L for C++14
  • __cplusplus is defined as 202002L for C++20

Clang Compiler

In the Clang compiler, the __cplusplus directive is defined as follows:

  • __cplusplus is defined as 199711L for C++98
  • __cplusplus is defined as 201103L for C++11
  • __cplusplus is defined as 201402L for C++14
  • __cplusplus is defined as 202002L for C++20

Microsoft Visual C++ Compiler

In the Microsoft Visual C++ compiler, the __cplusplus directive is defined as follows:

  • __cplusplus is defined as 199711L for C++98
  • __cplusplus is defined as 201103L for C++11
  • __cplusplus is defined as 201402L for C++14
  • __cplusplus is defined as 202002L for C++20

What Does the __cplusplus Directive Signify?

The __cplusplus directive signifies the version of the C++ standard being used by the compiler. This information can be used by programmers to write code that is compatible with different versions of the C++ standard. For example, if a programmer wants to write code that is compatible with C++11, they can use the following code:

#if __cplusplus >= 201103L
    // Code that is compatible with C++11
#endif

Possible Expansions of the __cplusplus Macro

The __cplusplus macro can be expanded in different ways depending on the compiler and the version of the C++ standard being used. Here are some possible expansions of the __cplusplus macro:

  • 199711L: C++98
  • 201103L: C++11
  • 201402L: C++14
  • 202002L: C++20
  • __cplusplus > 199711L: C++11 or later
  • __cplusplus >= 201103L: C++11 or later
  • __cplusplus > 201402L: C++14 or later
  • __cplusplus >= 202002L: C++20 or later

Conclusion

In conclusion, the __cplusplus directive is a preprocessor macro in C++ that provides information about the version of the C++ compiler being used. This macro is defined by the compiler and can be used by programmers to write code that is compatible with different versions of the C++ standard. In this article, we have explored how the __cplusplus directive is defined in various compilers and what it signifies.

Frequently Asked Questions

Q: What is the __cplusplus directive?

A: The __cplusplus directive is a preprocessor macro in C++ that provides information about the version of the C++ compiler being used.

Q: How is the __cplusplus directive defined in various compilers?

A: The __cplusplus directive is defined differently in various compilers. For example, in the GCC compiler, it is defined as 199711L for C++98, 201103L for C++11, 201402L for C++14, and 202002L for C++20.

Q: What does the __cplusplus directive signify?

A: The __cplusplus directive signifies the version of the C++ standard being used by the compiler.

Q: What are the possible expansions of the __cplusplus macro?

A: The __cplusplus macro can be expanded in different ways depending on the compiler and the version of the C++ standard being used. For example, __cplusplus > 199711L signifies C++11 or later, and __cplusplus >= 202002L signifies C++20 or later.

Q: How can I use the __cplusplus directive in my code?

A: You can use the __cplusplus directive in your code to write code that is compatible with different versions of the C++ standard. For example, you can use the following code to write code that is compatible with C++11:

#if __cplusplus >= 201103L
    // Code that is compatible with C++11
#endif
```<br/>
# Frequently Asked Questions About the __cplusplus Directive

Q: What is the purpose of the __cplusplus directive?


A: The __cplusplus directive is a preprocessor macro in C++ that provides information about the version of the C++ compiler being used. This information can be used by programmers to write code that is compatible with different versions of the C++ standard.


Q: How is the __cplusplus directive defined in various compilers?


A: The __cplusplus directive is defined differently in various compilers. For example, in the GCC compiler, it is defined as 199711L for C++98, 201103L for C++11, 201402L for C++14, and 202002L for C++20.


Q: What does the __cplusplus directive signify?


A: The __cplusplus directive signifies the version of the C++ standard being used by the compiler. This information can be used by programmers to write code that is compatible with different versions of the C++ standard.


Q: What are the possible expansions of the __cplusplus macro?


A: The __cplusplus macro can be expanded in different ways depending on the compiler and the version of the C++ standard being used. For example, __cplusplus &gt; 199711L signifies C++11 or later, and __cplusplus &gt;= 202002L signifies C++20 or later.


Q: How can I use the __cplusplus directive in my code?


A: You can use the __cplusplus directive in your code to write code that is compatible with different versions of the C++ standard. For example, you can use the following code to write code that is compatible with C++11:


#if __cplusplus &gt;= 201103L
    // Code that is compatible with C++11
#endif
</code></pre>
<h2>Q: What is the difference between __cplusplus and __cplusplus_major?</h2>
<p>A: The <code>__cplusplus</code> macro provides information about the version of the C++ compiler being used, while the <code>__cplusplus_major</code> macro provides information about the major version of the C++ standard being used. For example, <code>__cplusplus</code> might be defined as <code>201103L</code> to indicate that the compiler is using the C++11 standard, while <code>__cplusplus_major</code> might be defined as <code>11</code> to indicate that the major version of the C++ standard being used is 11.</p>
<h2>Q: Can I use the __cplusplus directive to detect the version of the C++ compiler being used?</h2>
<p>A: Yes, you can use the <code>__cplusplus</code> directive to detect the version of the C++ compiler being used. For example, you can use the following code to detect the version of the C++ compiler being used:</p>
<pre><code class="hljs">#if __cplusplus &gt;= 201103L
    // Code that is compatible with C++11 or later
#elif __cplusplus &gt;= 201402L
    // Code that is compatible with C++14 or later
#elif __cplusplus &gt;= 202002L
    // Code that is compatible with C++20 or later
#else
    // Code that is compatible with earlier versions of the C++ standard
#endif
</code></pre>
<h2>Q: Are there any limitations to using the __cplusplus directive?</h2>
<p>A: Yes, there are some limitations to using the <code>__cplusplus</code> directive. For example, the <code>__cplusplus</code> directive is not defined in all compilers, and its value may not be what you expect. Additionally, the <code>__cplusplus</code> directive may not be defined for all versions of the C++ standard.</p>
<h2>Q: Can I use the __cplusplus directive in a header file?</h2>
<p>A: Yes, you can use the <code>__cplusplus</code> directive in a header file. However, you should be careful when using the <code>__cplusplus</code> directive in a header file, as it may not be defined in all compilers.</p>
<h2>Q: Can I use the __cplusplus directive to detect the version of the C++ standard being used?</h2>
<p>A: Yes, you can use the <code>__cplusplus</code> directive to detect the version of the C++ standard being used. For example, you can use the following code to detect the version of the C++ standard being used:</p>
<pre><code class="hljs">#if __cplusplus &gt;= 201103L
    // Code that is compatible with C++11 or later
#elif __cplusplus &gt;= 201402L
    // Code that is compatible with C++14 or later
#elif __cplusplus &gt;= 202002L
    // Code that is compatible with C++20 or later
#else
    // Code that is compatible with earlier versions of the C++ standard
#endif
</code></pre>
<h2>Q: Are there any best practices for using the __cplusplus directive?</h2>
<p>A: Yes, there are some best practices for using the <code>__cplusplus</code> directive. For example, you should always check the value of the <code>__cplusplus</code> directive before using it, and you should be careful when using the <code>__cplusplus</code> directive in a header file. Additionally, you should consider using the <code>__cplusplus_major</code> macro instead of the <code>__cplusplus</code> macro to detect the major version of the C++ standard being used.</p>