Question

I ‘ve been struggling for more than 3 hours but cannot find a solution.
A simple helloworld program is running nicely and I can get the output,

 #include<iostream>
    #include<string>

    using namespace std;
    int main(){
       string s;
       cout<<"hello world";
    }

But for the My Sudoku Project I have the following user defined header
files, SudokuSolver.h, Matrix.h, Cell.h, Pos.h, Error.h, Exception.h and
their corresponding .cpp files.

And ExampleProgram.cpp uses these header files, to solve a Sudoku.

(All the .h and .cpp files are in a same folder.)

I have included using namespace std; and I included the string as #include <string>.
in each header file, wherever I used string.h. But even though I am getting the fatal error: string: No such file or directory compilation terminated. when I run as

g++ ExampleProgram.cpp SudokuSolver.h Cell.h Error.h Pos.h Matrix.h

When I compile the ExampleProgram.cpp as

 g++ -c ExampleProgram.cpp SudokuSolver.h
 Cell.h Error.h Pos.h Matrix.h       

I am getting no error.

When I run the ExampleProgram.cpp using ./a.out I am not getting the output for my sudoku solver. Rather I am getting the output of my previously runned helloworld program. It shows my ExampleProgram.cpp has not successfully compiled. But as previously said

g++ -c ExampleProgram.cpp  SudokuSolver.h 
    Cell.h Error.h Pos.h Matrix.h       

doesn’t give any error.

This is my output:

[fosslab@fosslab SudokuSolver]$ g++ -c Error.h
[fosslab@fosslab SudokuSolver]$ g++ -c Exception.h
[fosslab@fosslab SudokuSolver]$ g++ -c Matrix.h
[fosslab@fosslab SudokuSolver]$ g++ -c Cell.h
[fosslab@fosslab SudokuSolver]$ g++ -c Pos.h
[fosslab@fosslab SudokuSolver]$ g++ -c SudokuSolver.h
[fosslab@fosslab SudokuSolver]$ g++ -c ExampleProgram.cpp SudokuSolver.h Excepti
on.h Cell.h Error.h Pos.h Matrix.h                                             
[fosslab@fosslab SudokuSolver]$ ./a.out
hello world[fosslab@fosslab SudokuSolver]$ 

Answer 1

First of all, header files a meant to be included in the source files. Do not add them to the command line for the compiler.

Secondly, the command line argument “-c” to g++ tells g++ to not link and make an executable file, but only make an object file.

You should either do:

$ g++ -c ExampleProgram.cpp
$ g++ ExampleProgram.o

or

$ g++ ExampleProgram.cpp

In both the above cases you will get a new “a.out” executable program.

If you have several source files, then compile them and not the header files:

$ g++ -c Error.cpp
$ g++ -c Exception.cpp
$ # etc...
$ g++ -c ExampleProgram.cpp
$ g++ Error.o Exception.o ... ExampleProgram.o