Already defined” linker error

This error is very com­mon, when you try to com­pile in Visu­al Stu­dio a huge cross-plat­form C++ project.

This is because of stan­dart C++ tem­plates, that are released in Visu­al Stu­dio libs and in addi­tion­al UNIX libs too. So, you have to exclude one of them to use anoth­er.
Just add one of them, go to Project Prop­er­ties / Link­er / Input / Ignore Spe­cif­ic Default Libraries and add the stan­dard lib that pro­duces con­flict. For me it was enough to add LIBCMT.LIB.