Hints for Using C++

C++ Compilers

g++: The GNU C++ compiler

• Available on DECs, IBM's Suns, HPs
• Example: g++ myprog.cc

xlC: C++ compiler

• available on IBMs
• Example: xlC myprog.C

CC: C++ compiler

• available on HPs
• Example: CC myprog.cc

Read the man pages for each compiler to determine the various compiler flags (e.g. -g for inserting debugging symbols) and allowable file extensions

Compiling a Program in a Single File

Compiling a program in a single file simply involves giving the compiler the filename of a C++ source program:

        g++ reverse1.cc

This command compiles the program reverse1.cc and puts the object code into the file named a.out

Consider the program for this example, reverse1.cc:

  // a simple program to illustrate compiling.
  #include   
  #define MAX  5   // The maximum number of numbers we can input.
  
  //  Function reverse reverses inarray and places the result in revarray.
  void reverse(int inarray[], int revarray[]){
  
  int j;
    for (j=0;j<MAX;j++){
      revarray[j] = inarray[MAX - j -1];
    }
  }
  
  void main(){
  
  int i;
  int inarray[MAX];            // The input array
  int revarray[MAX];           // The reversed array
  
  cout<<"Enter 5 integers each followed by <return>" << endl;
  for (i=0;i<MAX;i++){
    cin >> inarray[i] ;           // Get the five numbers.
  }
  
  reverse(inarray,revarray);     // Call our reverse function.
  
  cout << "The integers you input are: " << endl;
  
  for (i=0;i<MAX;i++){          // print out inarray
    cout << inarray[i] << " ";
  }
  
  cout << endl;
  
  cout << "The integers in reverse order are: " << endl;
  
  for (i = 0;i<MAX; i++){       // print out revarray.
    cout << revarray[i] << " " ;
  }
  
  cout << endl;
  }

Compiling with Multiple Files

Compiling with multiple files involves a little more work

We can compile the files separately into object files with the -c compiler option and then use the compiler to link them together and put them in a file named a.out

g++ -c revlib.c	Make the first object file
g++ -c rev2.cc	Make the second object file
g++ rev2.o revlib.o	Now link them into an executable

As programs get larger and involve more files this method becomes cumbersome

Makefiles: An alternative method is to use a makefile

After creating a file called makefile (or Makefile) in the same directory as the source files, one invokes the make program by typing

       make

Make is initially discussed in CS 200 and later in CS 314

Example makefile:

  rev2: rev2.o revlib.o
          g++ -o rev2 rev2.o revlib.o
  
  rev2.o: rev2.cc
          g++ -c rev2.cc
  
  revlib.o: revlib.cc revlib.h
          g++ -c revlib.cc
  
  clean:
          rm rev*.o *~

Note: The indented lines in any makefile must begin with a tab character; if the first character of an indented line is a space, an error message is returned whenever the makefile is used

rev2.cc: The main file of a sample program with multiple files

  // A simple program to illustrate how to link multiple files together.
  # include 
  # include "revlib.h"   
  
  void main(){
  
  int i;
  int inarray[MAX];            // The input array
  int revarray[MAX];           // The reversed array.
  
  cout<<"Enter 5 integers each followed by " << endl;
  for (i=0;i<MAX;i++){
    cin >> inarray[i] ;       // Get the input from stdin
  }
  
  reverse(inarray,revarray);  // Reverse the input array.
  
  cout << "The integers you input are: " << endl;
  
  for (i=0;i<MAX;i++){       // Print inarray
    cout << inarray[i] << " ";
  }
  
  cout << endl;
  
  cout << "The integers in reverse order are: " << endl;
  
  for (i = 0;i<MAX; i++){    // Print revarray
    cout << revarray[i] << " " ;
  }
  
  cout << endl;
  }

revlib.h: A header file for this sample program

  #ifndef __REVLIB_H__
  #define __REVLIB_H__
  #define MAX 5
  
  void reverse(int inarray[],int revarray[]);
  #endif

revlib.cc: Another file for the sample program

  // A simple library file to reverse an array and place it in another array.
  #ifndef __REVLIB_CC__
  #define __REVLIB_CC__
  
  #include "revlib.h"
  
  void reverse(int inarray[], int revarray[]){
  // We assume the caller is taking care of matching the size of revarray 
  // and inarray!
  int j;
  
    for (j=0;j<MAX;j++){
      revarray[j] = inarray[MAX - j -1];
    }
  }
  #endif

More C++: Templates

      stack<float> FakeStack;