Make Reimplementation

This is a reimplementation of the Linux command "make" and is a course project of CS537.

Detailed description of the command can be found on the webpage: http://pages.cs.wisc.edu/~bart/537/programs/program3.html

Now that the webpage is no longer accessible.

This program is written in C and can only be executed on Linux machines.

Compiling

This program uses GCC compiler and the pthread library. Since there is a makefile, just use "make" to compile the program.

Running

Here are 2 examples of running:

./537make

./537make main.o

Since this program implements the basic functionalities of make, it can be used just like the Linux command "make" to compile normal C programs.

Program Structure

This program can be divided into 5 parts.

• Main File
• Build Specification
• Command line Execution
• Specification Graph
• Text Parsing

Main file

The main function of the program is in it.

Build Specification

A typical makefile may look like this:

all: Build.o main.o progexec.o specgraph.o text_parsing.o
	gcc -o 537make Build.o main.o progexec.o specgraph.o text_parsing.o
Build.o: Build.c Build.h
	gcc -Wall -Wextra -c Build.c
main.o: main.c specgraph.h progexec.h text_parsing.h
	gcc -Wall -Wextra -c main.c
progexec.o: progexec.c progexec.h
	gcc -Wall -Wextra -c progexec.c
specgraph.o: specgraph.c specgraph.h progexec.h
	gcc -Wall -Wextra -c specgraph.c
text_parsing.o: text_parsing.c text_parsing.h
	gcc -Wall -Wextra -c text_parsing.c

clean:
	rm Build.o main.o progexec.o specgraph.o text_parsing.o
	rm 537make

A build specification is a struct with 3 fields.

• Target
• Dependence
• Command Line

Take a snippet of the makefile above:

Build.o: Build.c Build.h
	gcc -Wall -Wextra -c Build.c

In this case,

• The target is "Build.o".
• The dependence is "Build.c" and "Build.h".
• The command line is "gcc -Wall -Wextra -c Build.c"

Command Line Execution

This parts executes a command line in the C program by forking a child process.

The command line that is to be executed are gcc commands, such as:

gcc -Wall -Wextra -c Build.c

Specification Graph

Sometimes the make program needs to deal with bad makefile. The makefile might contain cycles in dependencies. For example:

main1.c: main2.c
    echo building main1.c!
main2.c: main1.c
    echo building main2.c!

To deal with the situation, a graph of build specification is created, and cycle detection algorithm is applied to the graph. If a cycle is detected, the program stops making.

Text Parsing

This part parses the text in the makefile and returns an "ArrayList" of all the build specifications.

Development Procedure

Ying Zhang coded the part of reading makefile and constructing build specifications, Kenny Jin finished the part of program execution and graph operations.