I set myself a challenge: write a self-hosting C compiler in 10 hours. This is the result, plus lots of cleanup (check "releases" for the 10 hour version).
Implementation:
- Generates 32-bit x86 assembly, which is then assembled and linked by GCC.
- It is all implemented in a single pass. Code generation is mixed with parsing. This requires some creativity.
- The compiler has to guess whether an expression will be used as an lvalue ahead of time. Trouble!
Language:
- Local and global variables, parameters.
- Functions,
if,while,return,break. =,?:(ternary),||,&&,==,!=,<,>=,+,-,*,++,--(post-ops),!,-,*(unary),[],()- The language it implements is typeless. Everything is a 4 byte signed integer.
- Pointer indexing works in increments of 4 bytes, pointer arithmetic is byte-by-byte.
The general philosophy was: only include a feature if it reduces the total code size.
git clone http://github.com/Fedjmike/mini-c
cd mini-c
make selftest
This will first produce cc by compiling mini-c with GCC. Then it makes ccself by compiling mini-c with cc. Finally it makes test/triangular using ccself, and checks the result. You should get something like this:
$ make selftest
gcc -std=c11 -Werror -Wall cc.c -o cc
cc cc.c
gcc -m32 a.s -o ccself
ccself tests/triangular.c
gcc -m32 a.s -o triangular; triangular 5; [ $? -eq 15 ]
If you are on Windows, you will need to checkout the windows branch. On 64 bit Linux, you may need to sudo apt-get install gcc-multilib to be able to compile and run the 32 bit code.
Another microscopic C compiler is c4 by rswier. He implemented more C, but I'd say mine is simpler :). Also, c4 generates code for its own VM, whereas mine has the significant difficulty of working with x86 assembly and cdecl.
I wrote another, much more advanced C compiler. Check it out. It too is self-hosting, but with a much more complete feature set, and even some experimental additions like lambdas.