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Make will automatically rebuilt only the updated files.Ĭharacter # starts a comment. This speeds up the compilation when you have many source files in your project, and change only a few of them at a given time. This time, however, it uses an intermediate step during which it compiles each cpp source file into an object file bin/*.o. It will instruct g++ to build the program from these files. It automatically searches the subdirectory src for all *.cpp source files and all *.h header files. The improved makefile is much more convenient. Now running make again will just print that bin/myprogram is up to date. $ cd ~/testproj $ rm bin/* $ make g++ src/extra.cpp -O3 -c -o bin/extra.o g++ src/main.cpp -O3 -c -o bin/main.o g++ src/other.cpp -O3 -c -o bin/other.o g++ bin/extra.o bin/main.o bin/other.o -O3 -o bin/myprogram $ bin/myprogram Hello Try building your project by running make: #Write simple makefile for c program how to# -O3 tells g++ to optimize the code for speed CC_OPTS := -O3 # this variable will contain the names of all cpp source files SRCS :=$( wildcard src/*.cpp ) # variable with all header files HEADERS :=$( wildcard src/*.h ) # this will contain the names of all intermediate object files OBJECTS :=$( patsubst src/%.cpp, bin/%.o, $( SRCS )) # this rule is fancier now # $< are the names of all prerequisites (the object files) # is the name of the target (bin/myprogram in this case) bin/myprogram: $( OBJECTS ) $( CC ) $^ $( CC_OPTS ) -o # must start with TAB character # but now we have to tell make how to build the object files # -c option tells g++ to only compile one source file at a tile # $< is the name of the first prerequisite (the cpp file in this case) bin/%.o: src/%.cpp $( HEADERS ) $( CC ) $< $( CC_OPTS ) -c -o # must start with TAB character #Write simple makefile for c program free# we can define variables in a makefile # variable CC will specify the compiler feel free to use clang++ CC := g++ # this variable contains any extra compiler options that we might # want to add, like -O3, -march=native, etc. Copy the following source ( the makefile is available at this link) into your makefile (again, make sure that lines 23 and 29 start with a single TAB character): Lets try to write a more general makefile for our project. The second line must start with a single TAB character to work properly. Here it is as simple as running g++ with the names of the source files (make will replace $^ with their names automatically), and the name of the output file (make will replace by bin/myprogram). ![]() The second line then explains how to build bin/myprogram. When writing makefiles, bin/myprogram is called the target, and the source files are the prerequisites of building the target. That means that whenever one of these files changes, make will try to rebuild bin/myprogram. The first line tells make that the building program bin/myprogram depends on three files: src/extra.cpp, src/main.cpp and src/other.cpp. $ make -B g++ src/extra.cpp src/main.cpp src/other.cpp -o bin/myprogram Explanation To create this for testing in a directory ~/testproj, run the following commands in the terminal (lines starting with $ specify which command you should run in your bash shell, lines without $ give you the output of the previous command): So let’s assume that you have the directory structure as described above. The makefile specifies rules that Make will follow when generating intermediate files. Make uses makefiles (a file at the root directory of your project called makefile) to build your project. Src/: The subdirectory that will contain all you source files ( *.h, *.hpp, *.c, *.cpp, etc.)īin/: This is the subdirectory where the compiler will create the binary files and the final executable. Makefile: The makefile that will be described below project/home/dir/: This is the home directory of your project. This is usually also the way how IDEs like Eclipse organize the project files. I prefer separating source files and binary files into their own directories. #Write simple makefile for c program installOn Windows, again, one can install it through Cygwin… Cygwin will also supply the GCC toolchain. All commands described below assume that you are using the bash shell, which is the default shell on Linux/OS X. For one thing, GNU Make is not installed by default, so you will have to install it yourself. #Write simple makefile for c program windowsOn Windows things are a little bit more complicated. #Write simple makefile for c program mac osI am assuming that you are using Linux or Mac OS X. Jump directly to the makefile if you are not interested in the explanation. This is a short, quick introduction to using GNU Make to automatically build your C/C++ project’s executable. ![]() ![]() Quick introduction to GNU Make Quick introduction to GNU Make Norbert Pozar ![]()
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