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
