与stdio.h对应的库文件是动态链接还是静态链接

Question

I mean the math library is dynamically linked.So i was thinking that library files corresponding to stdio.h( printf and scanf codes ) are dynamically linked ? Also when we include stdio.h , then all functions declared in it are added at run time or only those functions which are used ?

Answer 1

On Linux and many other *nix systems, you typically link the C standard library dynamically, it's the default with gcc and clang . But you're still free to link statically if you want to. It entirely depends on your system, environment, toolchain and personal settings.

Also when we include stdio.h , then all functions declared in it are added at run time or only those functions which are used ?

Including a header doesn't link anything. The C standard library is linked automatically by C compilers, otherwise you would get undefined reference errors at the linking step if you use functions that are declared in eg stdio.h .

That said, with dynamic linking, the whole library is loaded at runtime when it is needed by the dynamic linker -- there's no way to load individual functions. The benefit with dynamic linking is that the OS only needs a single copy of this library, no matter how many processes link to it. The library can just be mapped in every processes address-space that needs it. This saves RAM at runtime.