Jul 13, 2018 · Here, we discuss the basic rules of C++ header file inclusion needed to simplify header file management. A header file should be included only when a forward declaration would not do the job. The header file should be so designed that the …

Sep 18, 2010 · In general square brackets are used to include system headers and external headers, while double quotes are used to include local files. There is a grey zone on whether a library in the same project should be considered as local or external.

Jun 9, 2010 · The only time you should include a header within another .h file is if you need to access a type definition in that header; for example: #ifndef MY_HEADER_H #define MY_HEADER_H #include <stdio.h> void doStuffWith(FILE *f); // need …

This article is meant to address a common newbie problem regarding failure to understand #include, headers, and source file interaction. Several good practices are outlined and explained to show how to avoid some ugly snags.

Jan 11, 2024 · A header file contains the set of predefined standard library functions. The header file can be included in the program with the C preprocessing directive "#include". All the header files have ".h" extension. Syntax: #include <header_file> / "header_file" Here, #: …

Jan 4, 2025 · In lesson 2.11 -- Header files, you learned that you can put function declarations in a header files. Then you can #include those functions declarations into multiple code files (or even multiple projects). Classes are no different.

Feb 27, 2025 · A header file should #include any other headers containing functionality it needs. Such a header should compile successfully when #included into a .cpp file by itself. Only #include what you need (don’t include everything just because you can). Do not #include .cpp files.

Nov 8, 2014 · Precompiled headers don't help that. The general rule of thumb is: include what you use. If you use an object directly, then include its header file directly. If you use an object A that uses B but do not use B yourself, only include A.h.

Headers generally contain declarations; cpp files contain definitions. When you include a file with definitions more than once, you get duplicates during linking. In your situation one defintion comes from foo.cpp, and the other definition comes from main.cpp, which includes foo.cpp.

Aug 2, 2021 · You make the declarations in a header file, then use the #include directive in every .cpp file or other header file that requires that declaration. The #include directive inserts a copy of the header file directly into the .cpp file prior to compilation.