Compiling a Multi-File Program

• Compiling a Two File Program (.h and .cpp)
• Use the -I flag to find any #include files that are not part of the language
• g++ -o <execname> -I. <filename>.cpp compiles a file filename.cpp, which includes the filefile.h #include  into an executable named execname
• The '.' that appears after the -I stands for the current working directory
• Compiling a Multi-File Program
• Example files:

// file1.h
const int magic_number = 1492;
long multiply_by_MN (int number);

// file1.cpp
#include <file1.h>
long multiply_by_MN (int number) {
  return (long)(number * magic_number);
}

// main.h
constant int loop_n_times = 4;

// main.cpp
#include <iostream.h>
#include <file1.h>
#inlcude <main.h>
int main() {
  // includes a call to multiply_by_MN()
  // uses constant magic_number
}

• g++ -c -I. file1.cpp creates the object code file file1.o, for the file file1.cpp
• g++ -c -I. main.cpp creates the object code file main.o, for the file main.cpp
• g++ -o <execname> main.o file1.o creates an executable by linking the object code for main.o, file.o, and any default libraries together