Question

I am starting some work using a third party library and when building it in Visual Studio 2010, I noticed I was receiving this linker warning many times (LNK4221). I looked at the sources used in creating the object files that were being linked and found that all of the implementation for these is located in the header files. Interestingly, I also noticed the project included corresponding .cpp files containing only a #include for the header with the implementation.

I am curious – what is the point of this and why would I want to use this technique? If the .cpp files aren’t adding any value to the project, why shouldn’t I just remove them to get rid of the linker warnings?

I tried searching for similar questions, but didn’t find anything of interest. If you know of any, please link them.

Answer 1

I’m using this to make sure, that the header is at least in one file included at the first position. By doing so, I make sure that the header is compilable on it’s own.

To convence the linker to not issue a warning, one could use an external variable with a very large variable:

int variable_with_a_name_that_includes_the_file_name_somehow = 42;