The HolyC Programming Language - BETA

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/

Introduction

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.

Example

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;

Compatibility

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.

Building

There is a Makefile at the root of the repository that wraps CMake, it provides:

• make, will build the compiler
• make install install the compile
• make unit-test run the unit tests

However if you wish to use cmake directly, here's an example:

Create the Makefiles in ./build

cmake -S ./src \
  -B ./build \
  -G 'Unix Makefiles' \
  -DCMAKE_C_COMPILER=gcc \
  -DCMAKE_BUILD_TYPE=Release

Compile

make -C ./build

Install

make -C ./build install

This will install the compiler and holyc libraries for strings, hashtables, I/O, maths, networking, JSON parsing etc... see ./src/holyc-lib/.

Using the compiler

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
  -cfg     Create graphviz control flow graph as a .dot file
  -cfg-png Create graphviz control flow graph as a png
  -cfg-svg Create graphviz control flow graph as a svg
  -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

Control Flow Graph Example

Example code:

I32 Main()
{
  auto i = 1;

  for (I64 j = 0; j < 10; ++j) {
    "%d",j;
  }
  while (i) {
    printf("hello");
  }

  return 1;
}

Compiled with: hcc -cfg ./<file>.HC && dot -Tpng ./<file.dot> -o <file>.png Produces the following control flow graph. Note that in order to use -cfg-png or -cfg-svg it requires the use of graphviz

Differences

• 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.

Bugs

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.

Inspirations & Resources:

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

Want to ask questions?

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