Include h files

Also, many standard library headers do not have. Don't put using statements in your header files! We include the header file so that the compiler pulls in the declaration. After the compiler finishes compiling each. Typically, header files have an include guard or a pragma once directive to ensure that they are not inserted multiple times into a single.

Because a header file might potentially be included by multiple files, it cannot contain definitions that might produce multiple definitions of the same name.

The following are not allowed, or are considered very bad practice:. Use of the using directive will not necessarily cause an error, but can potentially cause a problem because it brings the namespace into scope in every. The following example shows the various kinds of declarations and definitions that are allowed in a header file:. Skip to main content. This browser is no longer supported.

Add a comment. Active Oldest Votes. Improve this answer. VE7JRO 2, 14 14 gold badges 21 21 silver badges 28 28 bronze badges. The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Linked Related 2. Hot Network Questions. Arduino Stack Exchange works best with JavaScript enabled. Parappa Parappa 7, 2 2 gold badges 33 33 silver badges 38 38 bronze badges. The forward declarations thing is interesting.

Parappa, forward declarations are very useful in circular reference scenarios. But would they be a good practice in other scenarios? Johnsyweb Johnsyweb k 23 23 gold badges silver badges bronze badges. I disagree. Including the whole world in H files increases the dependancy chain and therefore compile times. My answer didn't recommend including the whole world in the header file, I suggested including just enough so that the user of the API doesn't have to spend time searching for dependencies.

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