Question

EDIT: I know about include guards, but include files are not the issue here. I’m talking about actual compiled and already linked code that gets baked into the static library.

I’m creating a general-purpose utility library for myself in C++.

One of the functions I’m creating, printFile, requires string, cout and other such members of the standard library.

I’m worried that when the library is compiled, and then linked to another project that also uses string and cout, the code for string and cout will be duplicated: it will both be prelinked in the library binary the program is being linked with, and it will be again linked with the project that uses them itself.

The library is structured like this:

1. There is one libname.hpp file the programmer who uses the library is supposed to #include in his projects.
2. For every function fname declared in libname.hpp, there is an file fname.cpp implementing it.
3. All fname.cpp files also #include "libname.hpp".
4. The library itself compiles into libname.a which is copied to /usr/lib/.

Will this even happen?
If yes, is it a problem at all?
If yes, then how can I avoid this?

Answer 1

I’m worried that when the library is compiled, and then linked to another project that also uses string and cout, the code for string and cout will be duplicated

Don’t worry: no modern compilation system will do that. The code for template functions is emitted into object files, but the linker discards duplicate entries.