For example, it knows that a foo.o can be built from a foo.c, and it knows what the command to do so is. Since these files are (traditionally) written by hand, make has a lot of magic to let you shorten the rules. Make reads its rules from a file that is usually called a Makefile. (The above is not actual syntax: make wants the commands indented by a TAB characters, which I can't do in this editing mode. This rule tells make that the file foo.o depends on the files foo.c and foo.h, and if either of them changes, it can be built by running the command on the second line. It does this by following rules created by the programmer. It would be time-consuming to always compile everything after you change anything, so make is designed to only compile the parts that need to be re-compiled after a change. A typical C program consists of several modules (.c) and header files (.h). Make is useful for controlling the build process of a project. Gcc is a C compiler: it takes a C source file and creates machine code, either in the form of unlinked object files or as an actual executable program, which has been linked to all object modules and libraries. Make gets its knowledge of how to build your program from a file called the makefile, which lists each of the non-source files and how to compute it from other files. Make is a tool which controls the generation of executables and other non-source files of a program from the program's source files. The description from GNUmake is as follows: GNUmake is one popular implementation of make. It also tracks dependencies between various source files and object files that result from compilation of sources and does only the operations on components that have changed since last build. Make is a "build tool" that invokes the compiler (which could be gcc) in a particular sequence to compile multiple sources and link them together. The GNU Compiler Collection (usually shortened to GCC) is a compiler system produced by the GNU Project supporting various programming languages. Wikipedia page on GCC describes it as a "compiler system": It supports multiple languages, but does not knows how to combine several source files into a non-trivial, running program - you will usually need at least two invocations of gcc (compile and link) to create even the simplest of programs. If you want to learn more about make do visit these two articles which I found really helpful.Gcc compiles and/or links a single file. When you will run make, you can see the following in your pwd. If you need to specify your own file name, you need to specify make -f name-of-my-file-that-make-will-use make looks for makefile, if not found, Makefile. The program that understands this is make. So, we have written a Makefile that contain instruction to automate the compilation process. main.o : main.cpp div.h g++ -c main.cpp # Same for test.o test.o : test.cpp test.h g++ -c test.cpp One single executable divisonExecutable : main.o div.o # Read this as divisionExecutable depends on main.o div.o # But how is it produced? Hmm.using the below statement g++ main.o div.o -o divisonExecutable # starts with tab, I repeat tab #- # But main.o is not there? So specify how it is produced. ![]() # Makefile # Specify what I need in the end. ![]() Important : The statements starting with # are for humans and shall not be typed in the terminal. Let us consider a single program to divide 2 numbers. The program we are going to use is called make. The file that we are going to write is named Makefile. How to write the instructions in a file that will be executed by a program to automate the build (or loosely compilation) process. What about if I give you a list of instructions and a program, that can execute these instructions and do this compilation for you. Now, if I give you this source code, would you be able to compile it and get an executable that you can double click and the software starts running? This would be painful (if not difficult) even for an expert. ![]() The number could be as large as 1000 for complex projects like Adobe Photoshop or Google Chrome. Many of my students struggle to understand the C++ compilation when applied to multiple files that belong to same project.Ī C++ project, something that will give you one executable, can consists of multiple files. Make and CMake : Automating C++ Build Process
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