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Description

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A makefile is often used to simplify the compilation and build process of large software tools, via
the GNU make [2] command. The software installation targets are primarily UNIX like operating
systems. A typical makefile has the following structure [1]
target: dependencies
recipe(s)
Given a makefile filename and an optional target as command line arguments, your task is
to generate an executable ’mymake’, from a C program. It must parse the makefile and build a
dependency graph for the (optional) provided target. Also, execute the recipes for the said target,
by spawning a new process per recipe, via fork and exec, as determined by the graph traversal. If
no target is specified as a command line argument, the first target in the makefile is chosen.
Alternatively, if your first argument is a print flag (-p) followed by the makefile, you must only
print the target, dependencies, and recipes in the makefile. A second type of flag (-r) followed by
the makefile must print the recipe order of the target. Do not fork/exec the recipes when running
either of the flags. More details are described in the following three phases:
1.1 Parsing the input makefile
The makefile consists of multiple targets and each target describes the dependencies that must be
satisfied before executing the recipes within a target. Recipes, rules, and commands mean the same
thing. In this project makefile, each target can either have multiple dependencies with one recipe
in a new line. Targets and dependencies are separated by a colon (:). Multiple dependencies for
a target are separated by space. Each recipe for a target must be indented via a single tab (\t,
not 2/3/4/8 spaces). Recipes within the same target, must be executed in the order they appear.
Blank lines are optional and improve readability. More assumptions about the file are presented
later in the section 5
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To simplify your job, we will provide a helper function that reads the contents of the makefile
into a two dimensional char array. The first step is to parse these lines from a char array to accurately determine targets, dependencies, and recipes. We suggest adopting the technique described
in makeargv.c from the textbook http://usp.cs.utsa.edu/usp/programs/chapter02/. One sample
makefile is shown below:
all : dep1 dep2
ls -l
dep1: dep3
gcc -o file1.o -c file4.c file1.c
dep2:
gcc -o file3.o -c file3.c
dep3: dep4
gcc -o file2.o -c file2.c
dep4 :
mkdir myproject
The above makefile with no command line target, runs as ./mymake -p makefile in. It must print
the target name, the dependency count and recipe count for each of the target in the Makefile.
Output of one target can look like
target ’all’ has 2 dependencies and 1 recipe
Dependency 0 is dep1
Dependency 1 is dep2
Recipe 0 is ls -l
Similarly, you must print the remaining 4 targets, their respective dependencies and recipes to get
full credit for this phase.
1.2 Determining the order of recipes
The makefile 1.1 when run with the recipe flag option, must print the order of recipes, such as
running ./mymake -r makefile in on command line. It must pick all and look for recipes in the
order – dep4, dep3, dep1, dep2. Finally, it prints the following lines:
mkdir myproject
gcc -o file2.o -c file2.c
gcc -o file1.o -c file4.c file1.c
gcc -o file3.o -c file3.c
ls -l
Running mymake -r makefilename will print all the recipes in order of execution, and no targets
must be passed on the commandline.
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1.3 Fork and exec the recipes.
Using the data structures that model the graph, execute the recipes by forking a new process per
recipe. Your program should determine which recipes are eligible to run, execute those recipes,
wait for any recipe to finish, then repeat this process until all recipes finished executing.
Instead, if a project is run with a specific target, say dep2, ./mymake makefile in dep2, your
program must only print and then fork/exec one recipe: gcc -o file3.o -c file3.c
2 Implementation:
We will provide an example framework to get started and examples to test the code. However, you
are free to use your own implementation, without following the given structure. In the folder pa1,
the src folder contains the code, test contains the test cases . The data structure used to store
information about the target in desired ’container’ data structure looks like
typedef struct target_block {
char *name; //Target name
char *depend[MAX_DEP]; // dependencies of target
char *recipe[MAX_RECIPES_PT]; // recipes per target
unsigned char dep_count; // number of dependencies in target
unsigned char recipe_count; // number of recipes in target
unsigned char visited; // used in DFS
} target;
The dependency graph uses the result of topological sort [3] – an application of Depth First
Search algorithm. Given a set of targets, dependencies, and recipes, one must construct a directed
graph by determining the nodes and edges as targets and dependencies, respectively. Alternatively,
a less modular deisgn involves inserting the targets into a stack based on the DFS traversal, avoiding
building a graph.
3 Execution:
There are three ways to execute the project via
$ ./mymake filename [target]
$ ./mymake [-p] filename
$ ./mymake [-r] filename
Your executable can take upto two command line arguments. The filename argument is mandatory. If the optional arguments are provided, they must be in fixed positions. Any other variations
must error out.
4 Testing
As described in 2, to test your code against the provided test cases within the framework, run $
make -i test-main. The -i flag ignores the error return value and lets you test the whole suite. We
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will use more tests cases than the ones provided. If you have not attempted extra credit, discussed
later, you must modify the makefiles to suit your code.
5 Assumptions:
To simplify the project, you can assume the following about the makefile:
• The makefile is well formed and has no circular dependencies.
• It doesnt use make variables (denoted via $), macros, or wildcards.
• It can have a maximum of 128 lines and each line is upto 128 characters long
• Each target can have upto 8 dependencies and one recipe. This assumption is relaxed, if you
are attempting extra credit.
• There can be no more than 128 targets in the makefile. Targets having 0 dependencies and
0 recipes, simulatenously, do not exist. However, targets with 0 recipes are possible.
• Recipes do not spread across lines
• We limit the executables to those found in default PATH environment of the CSELAB machines. Sample executables are Linux commands such as ls, cat, pwd, mkdir, or building an
executable via gcc.
• Each makefile has a single dependency tree.
• You are free to make any reasonable assumptions not stated in this document, but do mention
them early in your README file.
6 Extra credit:
Unlike the makefile described earlier, one can specify multiple recipes for a target. Multiple recipes
in different lines, within the same target, are executed in the order they are read. Recipes order
within the same line are from left to right. Also, multiple recipes can be solved in parallel by
separating them with a comma (,). For example, assume the following recipes in your makefile
named makefile ec
all : dep1 dep2
ls -l
dep1: dep3
gcc -o file1.o -c file4.c file1.c
dep2:
gcc -o file3.o -c file3.c
dep3: dep4
4
gcc -o file2.o -c file2.c
gcc -o file4.o -c file4.c
dep4 :
mkdir myproject, pwd
cat file1.c
By executing this makefile with no targets as $ ./mymake makefile ec. The program must pick all
and look for dependencies in the order — dep4, dep3, dep1, dep2. The recipes are executed as:
mkdir myproject
pwd
cat file1.c
gcc -o file2.o -c file2.c
gcc -o file4.o -c file4.c
gcc -o file1.o -c file4.c file1.c
gcc -o file3.o -c file3.c
ls -l
For dep4, do not execute cat file1.c until both the previous commands finished executing. The
parent must use wait system call on both the commands to avoid zombie process. If your group
chooses to attempt the extra credit for an additional 10% of the project grade, you must correctly
handle both parallel execution of recipes and multiple recipes per target, within the same program.
7 Deliverables:
One student from each group should upload to Canvas, a zip file containing their C source code
files, a makefile, and a README that includes the following details:
• The purpose of your program
• How to compile the program
• What exactly your program does
• Any assumptions outside this document
• Team names and x500
• Your and your partners individual contributions
• If you have attempted extra credit
The README file does not have to be long, but must properly describe the above points. Proper
in this case refers to – first-time user can answer the above questions without any confusion. Within
your code you should use one or two comments to describe each function that you write. You do not
need to comment every line of your code. However, you might want to comment portions of your
code to answer why, rather than how you implement the said code. At the top of your README
file and main C source file please include the following comment:
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/*test machine: CSELAB_machine_name
* date: mm/dd/yy
* name: full_name1, [full_name2]
* x500: id_for_first_name, [id_for_second_name]
*/
8 Grading Rubric:
1. 10% Correct README contents
2. 10% Code quality such as using descriptive variable names, modularity, comments, indentation. You must stick to one style throughout the project. If you do not already have a style
for C programming, we suggest adopting K&R style [4].
3. 15% for using meaningful data structures and appropriate error checking and handling
(a) 10% No program crashes or segfault
(b) 5% uses appropriate data structures
4. 20% Parse the makefile accurately – determined via -p flag
5. 15% Implement the dependency graph algorithm for identifying recipe order – determined
via -r flag
6. 30% Correctly call fork, exec, wait system calls not leading to fork bombs or zombie processes.
7. 10% Extra credit
If your code passes the test cases, you will get 75% of the credit. The remaining 25% depends
on the implementation quality and documentation, as described in points 1, 2 & 3b.
9 References:
1. Makefile rules: https://en.wikipedia.org/wiki/Makefile#Rules
2. GNU Make: https://www.gnu.org/software/make/manual/make.html
3. Topological sorting: https://en.wikipedia.org/wiki/Topological_sorting
4. K&R Style guide: https://en.wikipedia.org/wiki/Indentation_style#K&R_style
5. AND operator in make https://www.gnu.org/software/make/manual/make.html#Execution
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