Question

Objective-C has a runtime that translates its syntax into functions that are organized and compiled. Does C have a runtime library? Also, if anyone can answer the question, what are the steps GCC takes during C compilation? e.g. main.c >> main.s >> main.bin

Answer 1

Yes, the C language features a standard library; that is, a number of standard macros, routines and types one can use in his programs, apart from any in the core language itself.

In popular implementations, there is a separate library file containing the code for the C standard library. For example, in GNU/Linux environments, the GNU C library (libc) is almost always present. Microsoft provides the msvcrt.dll runtime library for the Windows system, and so on.

Also, the C standard library might not be available in freestanding implementations. Sometimes it is possible to compile a program without linking against the C standard library from your system. As an example, the Windows API is well known for behaving as a freestanding C programming environment (although one might need to link against other system libraries specific to Windows).

Regarding GCC, the following illustrates briefly the compilation pipeline:

1. The input source is preprocessed with GNU cpp, resulting in a translation unit. (Actually, as Basile pointed out, nowadays no cpp process is created; the entire preprocessing work is done within cc1. Nevertheless, the resulting behavior is most likely the same as with cpp.)
2. The translation unit is then interpreted and compiled to assembly source with GCC cc1;
3. The assembly source is then assembled into object code with GNU as;
4. Finally, object files and libraries are linked together to produce a binary image with GNU ld.

Naturally, each of these steps may be altered or not executed at all depending on the driver options; the above is just a rough explanation of the overall process.