please help - compiler error using GNU GCC compiler - unidentified reference to...

I'm new to c++ programming and started to work my way through the book Accelerated C++. When I tried to compile the program from Ch4 which had header files and source files I got these errors:

Code:

obj/Debug/main.o||In function `main':|
/home/x/Desktop/programming/4.0/main.cpp|26|undefined reference to `read(std::basic_istream<char, std::char_traits<char> >&, Student_info&)'|
/home/x/Desktop/programming/4.0/main.cpp|33|undefined reference to `compare(Student_info const&, Student_info const&)'|
/home/x/Desktop/programming/4.0/main.cpp|45|undefined reference to `grade(Student_info const&)'|
||=== Build finished: 3 errors, 0 warnings ===|

I tried to find a solution on my own but after hours of searching the only thing I learned is that its something about linking and my GNU GCC compiler. I'm using the IDE Code::Blocks.

Here is the main function and the header and source that are giving me the problems

Code:

int main()
{
    vector<Student_info> students;
    Student_info record;
    string::size_type maxlen = 0;       // the length of the longest name

    // read and store all the students data.
    // Invariant:  students contains all the student records read so far
    //   maxlen contains the length of the longest name in students
    while (read(cin, record)) {
        // find length of longest name
        maxlen = max(maxlen, record.name.size());
        students.push_back(record);
    }

    // alphabetize the student records
    sort(students.begin(), students.end(), compare);

    // write the names and grades
    for (vector<Student_info>::size_type i = 0;
         i != students.size(); ++i) {

        // write the name, padded on the right to maxlen + 1 characters
        cout << students[i].name
             << string(maxlen + 1 - students[i].name.size(), ' ');

        // compute and write the grade
        try {
            double final_grade = grade(students[i]);
            streamsize prec = cout.precision();
            cout << setprecision(3) << final_grade
                 << setprecision(prec);
        } catch (domain_error e) {
            cout << e.what();
        }
        cout << endl;
    }
    return 0;
}

My header file Student_info.h

Code:

#ifndef STUDENT_INFO_H_INCLUDED
#define STUDENT_INFO_H_INCLUDED

// Student_info.h header file
#include <iostream>
#include <string>
#include <vector>

struct Student_info {
	std::string name;
	double midterm, final;
	std::vector<double> homework;
};

bool compare(const Student_info&, const Student_info&);
std::istream& read(std::istream&, Student_info&);
std::istream& read_hw(std::istream&, std::vector<double>&);
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#endif // STUDENT_INFO_H_INCLUDED

My source file Student_info.cpp

Code:

#include "Student_info.h"

using std::istream;  using std::vector;

bool compare(const Student_info& x, const Student_info& y)
{
    return x.name < y.name;
}

istream& read(istream& is, Student_info& s)
{
    // read and store the student's name and midterm and final exam grades
    is >> s.name >> s.midterm >> s.final;

    read_hw(is, s.homework);  // read and store all the student's homework grades
    return is;
}

// read homework grades from an input stream into a `vector'
istream& read_hw(istream& in, vector<double>& hw)
{
    if (in) {
        // get rid of previous contents
        hw.clear();

        // read homework grades
        double x;
        while (in >> x)
            hw.push_back(x);

        // clear the stream so that input will work for the next student
        in.clear();
    }
}
    return in;

As far as I can tell, there is nothing wrong with my code, I double checked it with the book's code a few times. It's something to do with my compiler's method of linking and I don't know how to link or what option I need to change so that it does link.

Operating System : Linux (Ubuntu)
Compiler : GNU GCC Compiler
IDE : Code::Blocks

I don't know Code::Blocks, but are Student_info.cpp and Student_info.h part of the project?

You need to provide all the files to the compiler, not just one. Since you're using an IDE, that means you need to set up a project, put all the files in the project, and then build the entire project.

Yes all of the files are in the project, I can see them in my project manager. I think its something to do with the compiler and not the program itself.

You have them all in sources/headers as appropriate? What does your build log say?

Build log :

Code:

-------------- Build: Debug in 4.0 ---------------

Linking console executable: bin/Debug/4
obj/Debug/main.o: In function `main':
/home/x/Desktop/programming/4.0/main.cpp:26: undefined reference to `read(std::basic_istream<char, std::char_traits<char> >&, Student_info&)'
/home/x/Desktop/programming/4.0/main.cpp:33: undefined reference to `compare(Student_info const&, Student_info const&)'
/home/x/Desktop/programming/4.0/main.cpp:45: undefined reference to `grade(Student_info const&)'
collect2: ld returned 1 exit status
Process terminated with status 1 (0 minutes, 0 seconds)
3 errors, 0 warnings

Build messages :

Code:

||=== 4.0, Debug ===|
obj/Debug/main.o||In function `main':|
/home/x/Desktop/programming/4.0/main.cpp|26|undefined reference to `read(std::basic_istream<char, std::char_traits<char> >&, Student_info&)'|
/home/x/Desktop/programming/4.0/main.cpp|33|undefined reference to `compare(Student_info const&, Student_info const&)'|
/home/x/Desktop/programming/4.0/main.cpp|45|undefined reference to `grade(Student_info const&)'|
||=== Build finished: 3 errors, 0 warnings ===|

That is extremely interesting, because your build log should start with the command that was given.

My suggestion would be build-clean, make sure you've got both .cpp files listed in the sources thing on the left, and then build-build.

Ok thanks, ill try that and post back with my results