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We all know when to use include guard, but when shall we not use it in our project?
Recently, I saw a project with mix compilation (CUDA + GCC), one header file (CUDA file) is deliberately left without include guard. I am just curious about it.
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Formally, you don't need include guards in your bar. h . It has a single function declaration, which can be repeated many times in one translation units. So, including this header multiple times will not lead to errors.
Header guards are designed to ensure that the contents of a given header file are not copied, more than once, into any single file to prevent duplicate definitions. This is a good thing because we often need to reference the contents of a given header from different project files.
These user-defined types are typically defined in header files, so the type definitions can be propagated out to the code files that need to use them. Without a header guard, a code file could end up with multiple (identical) copies of a given type definition, which the compiler will flag as an error.
Such project header files should contain #include statements for the system headers; if the body includes them first, the compiler does not check this.
There are 2 scenarios off the top of my head:
assert.h works)
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One case in when you do want to include the same file several times with different parameters. In this case the include file would act as a sort of template. An example are the scalers on Dosbox.
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