An implementation of Terry A. Davis's HolyC

U0 Main()
{
  "Hello world\n";
}
Main;

Full documentation for the language can be found here: https://holyc-lang.com/

A holyc compiler built from scratch in C. Currently it is non optimising, walking the AST and compiling it directly to x86_64 assembly code as text which is fed into gcc to assemble. Floating point arithmetic is supported as are most of the major language features.

Below is a snippet of code showing some of the features supported by this holyc compiler. Namely inheritance, loops, printf by using a string and loops. All c-like control flows are supported by the compiler.

class SomethingWithAnAge
{
  I64 age;
};

class Person : SomethingWithAnAge
{
  U8 name[1<<5];
};

U0 ExampleFunction(U0)
{
  Person *p = MAlloc(sizeof(Person));

  MemCpy(p->name,"Bob",3);
  p->age = 0;

  while (p->age < 42) {
    p->age++;
  }
  "name: %s, age: %d\n",p->name,p->age;
  Free(p);
}

ExampleFunction;

Currently this holyc compiler will compile holyc source code to an x86_64 compatible binary which has been tested on amd linux and an intel mac. Thus most x86_64 architectures should be supported. Creating an IR with some optimisations and compiling to ARM is high on the TODO list.

Run make, then run make install (sudo make install on linux) this will install the compiler and holyc libraries for strings, hashtables, I/O, maths, networking, JSON parsing etc... see ./src/holyc-lib/

Once the compiler has been compiled the following options are available, they can be displayed by running hcc --help

HolyC Compiler 2024. UNSTABLE
hcc [..OPTIONS] <..file>

OPTIONS:
  -ast     Print the ast and exit
  -tokens  Print the tokens and exit
  -S       Emit assembly only
  -obj     Emit an objectfile
  -lib     Emit a dynamic and static library
  -clibs   Link c libraries like: -clibs=`-lSDL2 -lxml2 -lcurl...`
  -o       Output filename: hcc -o <name> ./<file>.HC
  -run     Immediately run the file (not JIT)
  -g       Not implemented
  -D<var>  Set a compiler #define (does not accept a value)
  --help   Print this message

• auto key word for type inference, an addition which makes it easier to write code.
• cast<type> can be used for casting as well as post-fix type casting.
• break and continue allowed in loops.
• You can call any libc code by declaring the prototype with extern "c" <type> <function_name>. Then call the function as you usually would. See here for examples.

This is a non exhaustive list of things that are buggy, if you find something's please open an issue or open a pull request. I do, however, intend to fix them when I get time.

• Using %f for string formatting floats not work
• Memory management for the compiler is virtually non-existent, presently all the tokens are made before compiling which is very slow.
• Line number in error messages is sometimes off and does not report the file
• Function pointers in a parameter list have to come at the end
• Variable arguments are all passed on the stack
• Casting between I32 and I64 is very buggy, the most obvious of which is calling a function which expects I64 and calling it with an I32 and vice versa, this will often cause a segmentation fault. As such prefer using I64 for integer types.
• The preprocessor for #define can presently only accept numerical expressions and strings. It is not like a c compilers preprocessor.

A lot of the assembly has been cobbled together by running gcc -S -O0 <file> or clang -s O0 <file>. Which has been effective in learning assembly, as has playing with TempleOS. The following are a non-exhaustive list of compilers and resources that I have found particularly useful for learning.

• TempleOS
• 8cc
• tcc
• cc65
• shecc
• JS c compiler

Find me on twitch: https://www.twitch.tv/Jamesbarford