Why do you have to link libraries AND set include directories

Hey so i'm a little confused on why, in msVS++ 2010 you have to have include directories when all the headers and cpp files are inside the static libray or stat开发者_JS百科ic library project in my case.

I made the static library project with cmake, and the source file i was told to set it to is the same i'm now told to make the include directory... it seems like I have 2 of the same cpp and header files.. except ones included statically in my sollution... WHY?

Because VS++ while abstracting the underlying implementation does not hide it completely.

Include directories and libraries are targeted at different phase of the process, which are traditionally handled by different programs. Include directories by the preprocessor, libraries by the linker. Those programs are now called (or part of?) VC++, but its interface still shows the underlying structure.

There are systems which allows to mark the needed libraries in the source code (and thus in the header) by the use of pragmas. Those have several disadvantages:

• non standard

• you can't as easily substitute libraries by another (say debug/instrumented/release, single thread/multi thread, ...)

Header files tell you about the functions you're calling.

Static libraries include the code of the function you're calling, but not information about how to call them.