This self-compiling subset of C is written in one 500 line file containing four functions. Branches add syntactic sugar like struct and switch. github 
Inspiration for Another Mini ARM C Compiler (AMaCC) built from scratch, supporting ARM architecture, with three execution modes: interpret, JIT or ELF for ARM. github
# Functions
next() scans for next token.
expr(int lev) compiles expressions.
stmt() compiles statements.
main(int argc, char **argv) alloc, compile and execute.
# Use
Bootstrap the compiler with gcc.
gcc -o c4 c4.c
Compile and execute one file.
./c4 hello.c
Compile the compiler which then executes to compile and execute the next argument.
./c4 c4.c hello.c
Nest the compiler-compiles which execute recursively.
./c4 c4.c c4.c hello.c