Homework 1

Due Date: January 14, 2000
100 Points

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1. (15 points) Chapter 1, exercise 8
2. (15 points) Chapter 1, exercise 9
3. (15 points) Robust Programming handout, exercise 8
4. (15 points) Robust Programming handout, exercise 12
5. (40 points) This exercise asks you to look at a standard UNIX C library for problems with robustness. Please write two programs that use functions from the strings library (the functions in that library are listed in the string(3) manual page). You are to call the functions in such a way that they cause the library function to crash, or generate unpredictable results. Turn in the following:
1. To demonstrate "crashing," use gdb output to show that the crash occured within the strings library function. That is, the program must call to the standard I/O library function, but cannot return from that call.
2. To demonstrate "unpredictable results," run your program (without changes) on at least two different types of computers in the CSIF (for example, once on a Linux system and once on an HP) and show that the results of the function differ (you can use gdb, or print the relevant values).
3. In both cases, please explain why the library routine answers. Support your hypothesis with references to the gdb output (or to source code, if that is available--but state how you know your version of the source code is the version actually installed!)
Please submit both the programs and typescripts for each program showing the crash or the unpredictable results. Important note: you must supply the correct type of argument for the functions. You may not, for example, pass a character pointer where a file pointer is expected.

Your two programs must not use the same technique to cause the problem. For example, if you discover a certain argument to strcat(3) causes a core dump, you cannot use that same argument to cause a core dump in strcpy(3). However, if a different argument will cause strcpy(3) to crash, feel free to use that.

You must submit a Makefile that we can invoke to compile your programs automatically. The compiled programs must be called "str1" and "str2". When you submit your program, please place your programs, Makefile, README, and any other relevant files into a subdirectory. Please call the directory string. Generate a tar file called string.tar. Use handin to submit string.tar. If we need to testit, we will un-tar it, run make, and execute str1 first, then str2.