Overall, it sounds like you are confused over the programming language. What language are you using?
There is no Codewarrior-supported language with a type called "String". C++ has the std::string type in the header <string>, not to be confused with <string.h> which is the C header for string handling functions.
If a C or C++ compiler can't link a library, it will tell you so when the linker is executed. You will not get runtime errors because of that, these are compiled languages, not interpreted. Runtime errors are most likely caused by bugs in the code or hardware issues.