Object files can refer to symbols that are not defined.
#MAKEFILE FOR C PROGRAM EXECUTABLE COMMAND CODE#
The assembler code generated by the compiler is assembled into the object code for the platform. The expanded source code file produced by the C++ pre-processor is fed to a compiler and compiled into the assembly language for the platform. Even a simple hello world program is transformed into a file with about 11'000 lines of code. The "pure" source code files can be really huge. It also adds special markers that tell the compiler where each line came from so that these can be used to produce sensible error messages. The output of this step is a "pure" C++ file without any pre-processor directives (which start with a #). The C++ preprocessor copies the contents of the included header files into the source code file, generates macro code, and replaces symbolic constants defined using #define with their values. In the example above the compilation process looks like this: save-temps tells the compiler to save all intermediate files to the compilation folder (pre-processed files, object files. However it is good practice to fix the code to get no warnings or errors at all. If warnings are the only messages you get when you compile your source code, an executable will still be created. Wall tells the compiler to show all warnings as they may describe possible errors in your source code. To compile for example a single main.cpp file containing a basic hello world application, one could use the g++ command to compile it into an executable binary: g++ -Wall -o Hello main.cpp -save-temps The C++ Compilation ProcessĬompiling a C++ source code file into an executable program is a four-step process. In this chapter a brief introduction in makefiles is given. While makefiles can be as complex as the projects they build, they are often generated or build step by step. This approach is also preferred as it allows for automated build processes and such. Makefiles are textual files that tell a compiler how the source code has to be build into an executable program. This is where makefiles can make our life's a little easier. However in the Linux and embedded world you do not always have these tools at your disposal. Modern IDE (Integrated Development Environments) such as Visual Studio and Eclipse have spoiled us a bit on this matter. This is a job for compilers and interpreters.Ĭompiling source code (the high-level language) can be a very complex job, especially when your project starts to become big and complex. This high-level language needs to be translated to binary processor instructions specific for the architecture the application will be running on. By expressing ourselves in a high-level language we can actually tell a computer or embedded system, which only understands low-level binary, what to do. Writing programs can be a fun thing to do.