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DAT2330 - Unix - Prof. Ian Allen
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Chapter 14 - Programming Tools (excerpts)

We will concentrate on the basic Compile, Link, and Go sequence.

Sections covered:

    Intro  p.537-541
    Compiling and Linking  p.541-543
    Compiler Warnings  p.551

Notes:

  - Usually when you are asked to "compile" a program, the intent is to
    compile it and link it into a runnable module.

  - The indentation used in the tabs.c program on p.539 is not standard.
    (The author did not indent inside functions.)  Since GNU/Linux is an
    open-source operating system, you can see "standard" C indentation
    style by reading the source code available.  You can find the Linux
    kernel source code under /usr/src/linux/ on the Linux Test Machine.
    A sample file would be: /usr/src/linux/kernel/time.c

NOTE: The IBM ACADAIX native compiler is named "cc", not "gcc",
      and it has a very different set of options.  The basic use of "-c",
      "-l", "-o" and a few others are the same as Linux (as they have
      been in use since 1975); but, the other options may be different.
      The ACADAIX "cc" compiler will accept both C language (*.c) and C++
      lanugage (*.C) source files.  Note the upper-case suffix!


Chapter summary:

  - Use the "-Wall" option to gcc (or to "g++") to turn on warnings
    about possible coding errors.  Use the "-g" option to generate symbol
    tables for symbolic debuggers such as "gdb".

  - If you don't use the "-o" option, the output load module, linked and
    ready to run, is left in the file "a.out" in the current directory.

  Compile and link a C program from several C source files:

    gcc -Wall -g one.c two.c three.c

  Compile several C source files into object code without linking:

    gcc -c -Wall -g one.c two.c three.c

  Link several object files (*.o) into one program without compiling:

    gcc -Wall -g one.o two.o three.o

  Compile and link a C++ program from several C++ source files:

    g++ -Wall -g -o myprog a.C b.C c.C

    (note the upper-case suffix!)

Here is some source code for some test programs:

  This version is C language:

    /******************************************************************/
    /* A program to print command line arguments -IAN! idallen@ncf.ca */
    /******************************************************************/
    #include <stdio.h>
	    int
    main(int argc, char **argv){
	    int i;
	    for( i=0; i<argc; i++ ){
		    printf( "Argument %d is '%s'\n", i, argv[i] );
	    }
	    return 0;
    }
    /*********************************************************/

  This version is C++ language:

    /******************************************************************/
    /* A program to print command line arguments -IAN! idallen@ncf.ca */
    /******************************************************************/
    #include <iostream.h>
	    int
    main(int argc, char **argv){
	    int i;
	    for( i=0; i<argc; i++ ){
		    cout << "Argument ";
		    cout << i;
		    cout << " is ";
		    cout << argv[i];
		    cout << "\n";
	    }
	    return 0;
    }
    /*********************************************************/

  Which program (C or C++) generates a smaller executable file?

Exercises for compiling and running on Linux:

  - Modify the argv program to display the arguments in reverse order,
    last to first, ending with argv[0] (the command name).  Compile and
    test the program with zero, one, and many arguments.  All tests should
    display the command name (argv[0]) last.

  - The strlen(str) function returns the integer length of its string
    argument.  Modify the argv program to print the argument length
    before the argument itself:
    
    $ ./a.out a bb ccc "d         d"
    Argument 4 length 11 is d         d
    Argument 3 length 3 is ccc
    Argument 2 length 2 is bb
    Argument 1 length 1 is a
    Argument 0 length 7 is ./a.out

    Compile and test the program with zero, one, and many arguments.

  - Modify the argv program to save the length of the longest and shortest
    arguments and print out the longest and shortest argument lengths
    and the actual text of those long and short arguments before the
    program exits.

    $ ./a.out aaa bb ccccccc ddd eee
    Argument 5 length 3 is eee
    Argument 4 length 3 is ddd
    Argument 3 length 7 is ccccccc
    Argument 2 length 2 is bb
    Argument 1 length 3 is aaa
    Argument 0 length 7 is ./a.out
    Min is 2 for bb
    Max is 7 for ccccccc

    Compile and test the program with zero, one, and many arguments.

Chapter 14 Chapter Review questions:

      2