Makefile Practice: Part 1 Making a Single Program without Templated.h Files: Get the MakeBasics folder from the CS260 repository.

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1 Makefile Practice: Part 1 Making a Single Program without Templated.h Files: Get the MakeBasics folder from the CS260 repository. You need to make a new file called MyMake with no extension in the MakeBasics directory. A good text editor will let you save a file with no extension less good ones will add.txt. Try making the file, if necessary, rename it in windows to remove.txt. (Must be viewing file extensions). The make file should show up in windows without an extension or fancy icon: A makefile consists of a set of rules, each with 3 parts: a target, a list of prerequisites and a command. The general syntax for a rule is: target: prerequisite-1 prerequisite-2... command The target and prerequisites are separated by a colon (:). The command must be preceded by a tab (NOT spaces). Hints: If the command is not preceded by a tab, you get an error message "makefile:4: *** missing separator. Stop." Some text editors like putting in spaces when you hit the tab key. You can either find the preference to disable this or use a different text editor (plain old Notepad works well) If a makefile is named Makefile it will be found automatically (do not need the -f flag when running MyMake). But QTCreator automatically creates its own makefiles with that name, so we are using MyMake In the makefile put the following: all: g++ -std=c++11 -o MyProgram.exe main.cpp Answer.cpp This defines a make target called all. (There is nothing special about that name, it could be anything you want.) It has no pre-requisites, meaning the rule all can happen no matter what. The command builds the file main.cpp using g++ (see Command Line tutorial for details). Save the file. Open a command prompt. Make sure compiler tools are on the path (try typing g++ to test). Navigate to the MakeBasics folder. Type: To run make and tell it to use the makefile MyMake. On Mac/Linux just use "make" and not "mingw32-make" The default behavior for make is to run the first target in the file. In this, case that is the target all. This should build MyProgram.exe, which you can then run from the command line.

2 Now add a second rule: Add the following to the file: all: g++ -std=c++11 -o MyProgram.exe main.cpp Answer.cpp del MyProgram.exe If you are on make/linux change "del" to "rm" in the last line Using the command prompt (should still be in the directory with your code) to do: clean This will run the rule with the target clean instead of the first rule. It should delete the exe To run the first rule again to build the program, you can either explicitly specify the all target: all Or rely on the fact that it is the default target because it is first: Compiling files separately: Make can also be used to set up multi-step compilations that only rebuild the necessary files. Change your makefile to: MyProgram.exe: main.o Answer.o g++ -std=c++11 -o MyProgram.exe main.o Answer.o main.o: main.cpp g++ main.cpp -std=c++11 -c g++ Answer.cpp -std=c++11 -c del main.o Answer.o MyProgram.exe Here, the rule for MyProgram.exe has some prerequisites: main.o and Answer.o This means that we need to verify that those files exist and are up to date before executing the command. If they do not exist or are not up to date, the make utility will automatically go (re)build them. If one of those files has been updated, we will need to rebuild the.exe. The command for MyProgram.exe builds using those object files (.o), not the raw.cpp files. The rule for main.o has a prerequisite: main.cpp This means main.cpp needs to exist before running this rule. There is no rule to create the.cpp that is the file you write. But listing it as a prerequisite means that if main.cpp is newer than main.o, we need to rebuild main.o. Also note about the main.o rule: - It compiles using -c which means compile only, do not try to link into a program - It does not use -o to specify an output file name. The default output file name will be main.o for main.cpp Execute: That will try to run the first rule, which first forces it to run the main.o rule, which builds main.o Then it has to run the Anser.o rule. Finally it actually does the MyProgram.exe rule Run it again: Nothing should be built since everything is up to date.

3 Go edit Answer.cpp to change the answer that is returned from getanswer(). Then rerun the make: This time, Answer.o should be rebuilt, since Answer.cpp has changed. Since Answer.o was rebuilt, MyProgram.exe also has to get rebuild. If you remove the prerequisites from the MyProgram.exe and Answer.o rules (delete the things after the : for each rule), and then repeat the last step, you will notice nothing gets rebuilt unless you completely delete it. Without the prerequisites listed for each rule, make has no idea what files it should look at to see if we need to rebuild. Part 2: Using Templated Headers: Get the MakeTemplatedproject from BitBucket and navigate to it. This folder has a main file that relies on Double.h, a file with a templated function and no corresponding.cpp. Create a file called MyMake and start with: ProgramA.exe: main.o g++ main.o -std=c++11 -o ProgramA.exe main.o: main.cpp Double.h g++ -std=c++11 -c main.cpp del ProgramA.exe main.o Notes about these rules: ProgramA.exe is the default rule since it is first. It has main.o as a prerequisite. It takes main.o and compiles it into ProgramA.exe. main.o has the Double.h file as a prerequisite. Since this.h has actual code, we need to make sure we rebuild if that files gets changed. However, we do not directly compile the.h file (it gets included from.cpp files), so Double.h does not appear on the next line. It is always safe to have.h files as prerequisites. It is essential to have them as prerequisites if they have templated code. From the command line try using the makefile to build the code: Try editing the.h file (even just put in a space and save). Then rerun the make utility and verify that the code gets rebuilt. If you want to skip building the separate object file, your makefile could look like: ProgramA.exe: main.cpp Double.h g++ main.cpp -std=c++11 -o ProgramA.exe del ProgramA.exe main.o

4 Part 3: Making Multiple Programs: Get the MakeComplex project from BitBucket and navigate to it. This folder has two files with main() functions two separate programs (A & B) that both rely on Answer.cpp and Templated.h, a file with a templated function and no corresponding.cpp. Only one program (main function) can be worked on in QTCreator at a time. To compile ProgramB in QTCreator, you would have to remove ProgramA.cpp from the project (without deleting it) and add ProgramB.cpp. To switch back to A, remove ProgramB.cpp and read ProgramA.cpp. Create a file called MyMake and start with: all: ProgramA.exe ProgramB.exe ProgramA.exe: programa.o Answer.o g++ programa.o Answer.o -std=c++11 -o ProgramA.exe ProgramB.exe: programb.o Answer.o g++ programb.o Answer.o -std=c++11 -o ProgramB.exe programa.o: programa.cpp Templated.h g++ -std=c++11 -c programa.cpp programb.o: programb.cpp Templated.h g++ -std=c++11 -c programb.cpp g++ -std=c++11 -c Answer.cpp del ProgramA.exe ProgramB.exe main.o Answer.o Notes about these rules: The rule all has program A and B as prerequisites. That means then need to be built (or rebuilt if out of date). After that, there is nothing actually to do, so there is no command on the next line. ProgramA.exe and ProgramB.exe rules build two different executables from the object files associated with all the.cpp files that are part of those programs. programa.o and program.o have the Templated.h file as a prerequisite. Since this.h has actual code, we need to make sure we rebuild if that files gets changed. However, we do not directly compile the.h file (it gets included from.cpp files), so Templated.h does not appear on the next line. It is always safe to have.h files as prerequisites. It is essential to have them as prerequisites if they have templated code. From the command line try using the makefile to build just programa: ProgramA.exe Note that the rule for making ProgramA.exe says we need both programa.o and Answer.o so they both get built first Then build just programb: ProgramB.exe Notice that it won't have to rebuild Answer.o even though that is a pre-requisite for ProgramB.exe as Answer.o exists already. Try deleting all the build product: clean Then building everything all

5 Extra: This section shows a bit more of the power of makefiles none of it is necessary for this class. Too much of those makefiles are hard coded That is where variables come in. We set a variable with: VARNAME = whatever To use a variable, we start with $ and enclose it within parentheses (...) or braces {...}. Single character variables do not need the parentheses. For example, $(VARNAME) or $@ That means we could rewrite the makefile to look like: FLAGS = -std=c++11 COMPILER = g++ all: ProgramA.exe ProgramB.exe ProgramA.exe: programa.o Answer.o $(COMPILER) $(FLAGS) programa.o Answer.o -o ProgramA.exe ProgramB.exe: programb.o Answer.o $(COMPILER) $(FLAGS) programb.o Answer.o -o ProgramB.exe programa.o: programa.cpp Templated.h $(COMPILER) $(FLAGS) programa.cpp -c programb.o: programb.cpp Templated.h $(COMPILER) $(FLAGS) programb.cpp -c $(COMPILER) $(FLAGS) Answer.cpp -c del ProgramA.exe ProgramB.exe main.o Answer.o

Command Line Navigation and Compiling

Command Line Navigation and Compiling You should become familiar with how to compile and work from the command line. Below is a quick reference and instructions on how to use the gcc c++ compiler (g++)