You are suppose to know how to write a Makefile already. If you don't, you should learn it as soon as possible because your Makefile must work in all your programming assignment submissions. There are a few tutorials on make on the web. Here are links to some of them. I have not really read through these pages so I cannot guarantee their correctness. Since I don't track these links, if they have moved, just google "makefile tutorial".

There is an example of a simple Makefile below.

Please be aware that if you transfer a Makefile from a Windows environment to a UNIX environment, chances are, it will not work. The reason is that a line in a text file in Windows ends with "\r\n" while a line in a text file in UNIX ends with just "\n". The extra "\r" can confuse make on UNIX machines. But I'm sure you can write a small program to fix that.

Compiling Your Code
For this class, you must write your program in C and you must use gcc as your compiler. You are also required to run the gcc command with the -g -Wall commandline options. The -g commandline option turns debugging to make your program debuggable and the -Wall commandline option turns on most of the useful gcc warnings. Compiling with this option will find many simple mistakes in your programs. If your program needs it, you should also link to the multithreading library that came with the system. (You are not permitted to include any library that was not installed in the 32-bit Ubuntu 16.04 system.)

For warmup1 and warmup2, you must use the gcc compiler that came with the 32-bit Ubuntu 16.04 system. Please understand that we will not accept any other compiler to be used to compiler your program for grading. If you code only works when it is compiled with a different version of the gcc compiler, you will not get any credit for it. To see what version of gcc you are running, please run the following command in a Terminal window:

    gcc --version
On a 32-bit Ubuntu 16.04 system, you should see that you are running gcc version 5.4.0. If you have accidentically upgraded your system and end up with a different version of gcc, please contact the instructor. Most likely, you will have to delete your 32-bit Ubuntu 16.04 system and reinstall everything to make sure that the grader will be able to compile your code!

If your program cannot be compiled with a required compiler and run on a required system, your program will not be graded (and it will get a grade of zero). Please understand that we are not permitted to write code for you (or fix your code to get it compiled).

Since grading of all programming assignments must be done on a 32-bit Ubuntu 16.04 machine running inside VirtualBox/VagrantBox, it's imperative that you make sure that your code can be compiled and run on a 32-bit Ubuntu 16.04 machine running inside VirtualBox/VagrantBox. Please understand that even if your code runs perfectly on some other systems, we cannot give you any partial credit for that.

We will evaluate your submission by copying all the files you have submitted into an empty directory on the grader's 32-bit Ubuntu 16.04 machine running inside VirtualBox/VagrantBox and then type the following command:

If an individual programming assignment spec has a more specific way of producing the required executables (which is typically the case), you must follow it. Minor variation (such as using gmake) is allowed, but you must describe in details how to compile your code near the top of your README file. The grader is not allowed to use a visual tool or an IDE to compile your code. If this does not produce the desired executable(s), you will probably lose a lot of points. You may lose quite a few points if the grader has to debug and modify your Makefile in order to get your code to compile. How many points you will lose depends on how hard it is for the grader to get your Makefile to work. You will receive a score of zero if we cannot find a way to compile your code without modifying your source code.

Here are some additional requirements (sorry about redundancy with the programming assignment specs):

  • You are required to use separate compilation to compile your source code. You must divide your source code into separate source files in a logical way. Even if everything can fit in a single source file, you must force yourself to cut it up or you will lose a lot of points! Please see the grading guidelines for details about the requirement.

  • You must not put the bulk of your code in header files! Header files are not where you are suppose to put your source code because you will lose the ability to debug your code.

  • When the following command is invoked at the UNIX prompt:
        make clean
    all binary files created during compilation (.o files, .gch files, executable files, etc.) must be removed.

  • You must use -Wall (or equivalent) in your Makefile when you compile with gcc and you must eliminate all compile-time warning messages.
By the way, if you think you have a perfectly working Makefile but when you run "make", you get an error message saying it does not know how to make a target, it's probably because you have created or modified your Makefile on a Windows machine and what you have is a DOS/Windows text file, which is not quite compatible with a Unix text file. In this case, you can either use "gmake" or run "dos2unix" to convert a DOS/Windows text file into a Unix text file.

When you compile, if you get warning messages saying that certain .c or .h file has no newline at end of file, then it's cause by the same problem (i.e., you have created these files in Windows). Please run "dos2unix" to convert such a DOS/Windows text file into a Unix text file.

A README file is the documentation of your submission. The filename you must use for a README is "x-README.txt" where "x" is an appropriate name for the assignment. You must download a README file template from the respective spec, edit it with a text editor by supplying all the required information, and then include it with your submission. You must not delete any line from the README file template or the grader will have to deduct points.

Such a README file includes the following sections:

  • A section called "BUILD & RUN" - This section contains instructions for creating the executable for your assignment. If all the grader has to do is to type "make", you are still required to say so in this section. Please note that minor variation on "make" is acceptable without penalty. Please read the instructions there.

    You are required to replace the first "(Comments?)" in this section with the command the grader should type to create your executable. This command should be the "make" command mentioned in the spec. You are required to replace the 2nd "(Comments?)" in this section with your response. Please understand that if you ask the grader to do something that's not consistent with what a grader is permitted to do, the grader will ignore what you asked. For example, the ONLY acceptable compiler is gcc and the grader is not permitted to use any IDE to compile your code. If you ask the grader to use anything else, the grader will not be allowed to comply and you will get a zero for your assignment if your code can only be compiled with another compiler or with an IDE. You will lose 0.5 point each if a "(Comments?)" in the answer part of this section is not replaced by a proper response.

  • A section called "SELF-GRADING" - This section contains your assessment of your submission. Each item in this section corresponds to an item in the grading guidelines. You are expected to run through the grading guidelines and give each item a grade. You must replace every "?" in this section with a numeric value (which should be a number ≥ 0 for anything in the "plus points" section and a number ≤ 0 for anything in the "minus points" section). If you give yourself a score of 0 for an item in the "plus points" section, the grader will give a 0 for that item and will not grade that item. You will lose 0.5 point each if a "?" in this section is not replaced by a proper value or if such a line is omitted.

  • A section called "BUGS / TESTS TO SKIP" - If there is a test that you don't want the grader to run because it may cause you to lose additional points elsewhere, please clearly state it in this section. Please read the instructions there. You are required to replace the "(Comments?)" in this section with either the word "none" or whatever appropriate information you want to provide. You will lose 0.5 point each if the "(Comments?)" in this section is not replaced by a proper response or if such a line is omitted.

  • A section called "ADDITIONAL INFORMATION FOR GRADER (Optional)" - If you have additional information for the grader, you can add them here. If you have no additional information for the grader, you can just leave it blank.

  • A section called "OTHER (Optional) - Not considered for grading" - This is just for you. The grader will not read this section even if you ask the grader to read it. You do not have to replace the "(Comments?)" in this section.
For kernel assignments, the README files are similar, although there are additional information you must provide. Please read the READE file template in the respective part of the spec carefully.

For warmup assignments, there is no requirement to use a fancy Makefile. You can just use a simple Makefile that contains 2 lines. The first line is the "target line" and it looks like:
    target: files
where target is the "target" of your "make" command and files is a space-separated list of source files and header files that make up your program.

For example, if you need to type "make foo" to create your executable, then "foo" is the "target". Typically, the "target" is the name of your executable file. If you need "foo.c", "bar.c", and "bar.h" in order to build the foo executable, then the first line of your Makefile can look like:

    foo: foo.c bar.c bar.h
The way you should read the above line is, "The foo target depends on foo.c bar.c bar.h." The idea here is that if any of files the target depends on changes and if you type "make target", the command in the line immediately follow the target line will get executed. There must be no blank character at the beginning of a target line.

The 2nd line is a line of command and it must begin with a <TAB> character and follow by a Unix/Linux command. Our simple Makefile can look like:

    foo: foo.c bar.c bar.h
            gcc -g -Wall -o foo foo.c bar.c
The leading blank space you see in front of the 2nd line must be a <TAB> character or this won't work! Also, there must be no intervening line between the target line and line of command. Using the above Makefile, if you type "make foo" and if foo.c, bar.c, or bar.h has changed, the "make" program will run the "gcc -g -Wall -o foo foo.c bar.c" command. (The command doesn't even need to have anything to do with compiling a program!)

In general, there can be multiple sections in a Makefile and a target can depend on other targets in another section of the Makefile (therefore, we can have a tree of dependencies). Each section starts with a target line and followed by one or more lines of commands. The target line must be have no leading space characters and each line of command must begin with a <TAB> character and you cannot have a blank link within a section. When you type "make target", the "make" program search the Makefile for a section whose target line contains the target of your "make" command, check the dependencies, and execute the corresponding lines of commands. For more details, please check out the recommanded tutorials mentioned at the top of this web page.

All warmup assignments also require that when you type "make clean", you must delete all generated binary files when you typed "make target" where "target" is the name of your executable file. In that case, your minimum "Makefile" must also contain a second section whose target is "clean" that depends on nothing and the command to execute should delete all generated binary files. The following is an example of such a file:

    foo: foo.c bar.c bar.h
            g++ -g -Wall -std=c++11 -o foo foo.c bar.c

            rm -f foo *.o
If you type "make clean", it will delete the file "foo" and all the files with a ".o" filename extension. If you create additional binary files (such as ".gch" files) when you "make", you must change the last line so that they also get deleted when you type "make clean".

How do you make sure that make would work? It's actually very simple.
  • Create a Makefile first time you need to compile your code. Don't wait till the last minute.

  • If you do your development on Windows or Mac OS X and expect your code to just compile and run on a 32-bit Ubuntu 16.04 system, you will soon find out how unrealistic your assumption is. I would leave at least 2 days for porting for small programming assignments and 5 days for porting large programming assignments from Windows/Mac to Ubuntu 16.04.

  • Write a rule in your Makefile to generate a submittable file in the right format (i.e., ".tar.gz"). Do this early! You can also think of this as generating a backup copy of what you have done so far. Copy the backup copy to another place in case you accidentically erase all your files.

  • Testing! Verify your submissions. Create an empty directory on your 32-bit Ubuntu 16.04 system, unpack your test submission, and type make in it! Then run through all the commands in the grading guidelines to make sure that you get a perfect score and check the "minus points" section to make sure that you have no deduction. If something doesn't work, fix it right away.

  • Have a working copy ready for submission. When it's 2 hours away from the deadline and your code is not completing working, you should probably consider doing the following.

    1. Fix your code so that it compiles and runs.

    2. Create a submission from your working code and keep it as a backup in case you can't fix your bugs when deadline comes.

    3. Repeat this as you fix more bugs.