Passing const CName as this argument discards qualifiers - c++

Question

I'm having trouble with passing a constant class through a function.
// test the constructors
auto CName nameOne("Robert", "Bresson");
const CName nameTwo = nameOne;
auto CName nameThree;
// display the contents of each newly-constructed object...
// should see "Robert Bresson"
cout << "nameOne = ";
nameOne.WriteFullName();
cout << endl;
// should see "Robert Bresson" again
cout << "nameTwo = ";
nameTwo.WriteFullName();
cout << endl;
As soon as the compiler hits nameTwo.WriteFullName() I get the error of abandoning qualifiers. I know that the class is a constant however I can't figure out how to work around it.
The function is in a header file written as so:
void const WriteFullName(ostream& outstream = cout)
{
outstream << m_first << ' ' << m_last;
}
I receive this error when const is put in back of the function header
main.cpp:(.text+0x51): undefined reference to `CName::CName()'
main.cpp:(.text+0x7c): undefined reference to `CName::WriteFullName(std::basic_ostream<char, std::char_traits<char> >&) const'
main.cpp:(.text+0xbb): undefined reference to `CName::WriteFullName(std::basic_ostream<char, std::char_traits<char> >&) const'
main.cpp:(.text+0xf7): undefined reference to `CName::WriteFullName(std::basic_ostream<char, std::char_traits<char> >&) const'
main.cpp:(.text+0x133): undefined reference to `operator>>(std::basic_istream<char, std::char_traits<char> >&, CName&)'
main.cpp:(.text+0x157): undefined reference to `operator<<(std::basic_ostream<char, std::char_traits<char> >&, CName const&)'
main.cpp:(.text+0x1f4): undefined reference to `operator<<(std::basic_ostream<char, std::char_traits<char> >&, CName const&)'
main.cpp:(.text+0x22b): undefined reference to `operator<<(std::basic_ostream<char, std::char_traits<char> >&, CName const&)'
main.cpp:(.text+0x25f): undefined reference to `operator<<(std::basic_ostream<char, std::char_traits<char> >&, CName const&)'
main.cpp:(.text+0x320): undefined reference to `operator<<(std::basic_ostream<char, std::char_traits<char> >&, CName const&)'
main.cpp:(.text+0x347): undefined reference to `operator>>(std::basic_istream<char, std::char_traits<char> >&, CName&)'

Answer 1

What you have is linker errors, which means that you don't link with all source files. I'm guessing that the code for the CName class is in a separate source file, and you forgot to build/link with it.
Edit: Compiling and linking multiple files
To make a program from more than one source file, you have to pass all the source files on the command line, like this:
$ g++ main.cpp cname.cpp -o myprogram
The above command uses both source files, and the -o option tells the compiler what to name the program.
You can also compile each source file separately and then link them together:
$ g++ main.cpp -c -o main.o
$ g++ cname.cpp -c -o cname.o
$ g++ main.o cname.o -o myprogram
The -c option tells the compiler to create an object file, that can later be used to link your program. The last command will not actually compile any sources, but instead uses the two object files to create the program.