Just another HolyC → C17 transpiler.
Or actually, the only one that works on Linux without requiring
a ring-0 operating system written entirely by one guy.
Reads .HC source, produces readable C17, compiles with GCC/Clang,
and runs. No TempleOS VM, no emulator, no "but actually you need
a 640x480 VGA output". Just code.
"I'd like to see RMS writing a HolyC compiler."
— Probably nobody, ever.
But here we are. Terry A. Davis built TempleOS and HolyC as an
operating system. We built holycc so you can run HolyC programs
on actual modern Linux machines without sacrificing your firstborn
to the VGA gods.
No TempleOS internals. No ring 0. No biblical references.
Just a compiler that works.
HolyC is the language created by Terry A. Davis (1969–2018) as the systems programming language for TempleOS — an operating system he built, entirely alone, from scratch, as an act of devotion.
holycc exists to carry that language forward. Not the operating system,
not the ring-0 architecture — but the language itself. A simple,
clean, expressive systems language that deserves to live beyond its
original home.
This project is a tribute. We reimplement with respect, ship with care, and release as free software — so that HolyC remains in the commons, forever.
"An operating system is a work of art."
— Terry A. Davis
"Also it runs in ring 0 and has 640x480 VGA."
— Also Terry A. Davis, probably
"I'm not a compiler developer, I just wrote a HolyC transpiler because someone had to and it wasn't going to be me, but here we are."
— The authors
git clone https://github.com/YOU/holycc.git && cd holycc
cmake -B build && cmake --build build
./install.sh # → ~/.local/bin, sets up 'hc' alias
# Write HolyC like a real TempleOS chad:
echo 'Print("Hello, world!\n");
return 0;' > hello.HC
holycc hello.HC # HolyC → C17 → binary
./hello # it just works| HolyC | C17 |
|---|---|
I8/I16/I32/I64 |
int8_t/int16_t/int32_t/int64_t |
U8/U16/U32/U64 |
uint8_t/uint16_t/uint32_t/uint64_t |
F64 |
double |
Bool |
bool |
Char |
char |
U0 |
void |
class/union/enum |
typedef struct/union/enum |
| Statement | |
|---|---|
| [ok] | if/else, for, while, do-while |
| [ok] | switch/case/default + implicit + range |
| [ok] | return, break, goto, labels |
| [ok] | class, union, enum |
| [ok] | asm/_asm, #define, #include |
| [ok] | #if/#else/#endif, #ifdef, #ifndef |
| [ok] | try/catch/throw |
| Category | |
|---|---|
| [ok] | Arithmetic, bitwise, logical, comparison |
| [ok] | Assignment, ternary, unary, cast |
| [ok] | . -> [] () & * sizeof |
| [ok] | Power operator ` |
| Feature | |
|---|---|
| [ok] | String auto-print: "hello\n"; |
| [ok] | Bare function call: MyFunc; |
| [ok] | Chained comparisons: 13 <= age < 20 |
| [ok] | Switch implicit case: case: |
| [ok] | Switch range: case 4...10: |
| [ok] | U0 procedure type |
| [ok] | public/private |
| [ok] | no_warn, reg/noreg |
| [ok] | offset(Vec2.y) |
| [ok] | offsetof |
| [ok] | Power ` |
| [ok] | has keyword |
| [ok] | argc/argv variadic |
| [ok] | Color literals $FF$ |
| [ok] | Class methods |
| [ok] | Top-level code (no main() needed) |
| Function | |
|---|---|
| [ok] | Print, PrintLn |
| [ok] | MAlloc, Free, MSize |
| [ok] | StrLen, StrCompare |
| [ok] | AtoI, AtoF |
| [ok] | MemSet, MemCpy, MemCompare |
| [ok] | CDelay, GetCh, PutChar |
| [ok] | Exit, SPrint |
| [ok] | pow() via <math.h> |
┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐
│ Source │ ──▶ │ Lexer │ ──▶ │ Parser │ ──▶ │ Semantic │ ──▶ │ CodeGen │ ──▶ C17 (.c)
│ (.HC) │ │ 114 tok. │ │ AST │ │ checks │ │ emitter │
└──────────┘ └──────────┘ └──────────┘ └──────────┘ └──────────┘
| # | Stage | Location |
|---|---|---|
| 1 | Lexer | src/lexer/ |
| 2 | Parser | src/parser/ |
| 3 | AST | src/ast/ |
| 4 | Semantic | src/semantic/ |
| 5 | Symbol Table | src/symbol/ |
| 6 | Type System | src/types/ |
| 7 | Code Generator | src/codegen/ |
| 8 | Runtime | runtime/ |
| 9 | CLI Driver | src/driver/ |
Every line committed to main must meet these standards:
| Rule | The standard |
|---|---|
| Language | C17 — no GNU extensions |
| Compiler | GCC ≥ 12 or Clang ≥ 15 |
| Build | CMake ≥ 3.16 |
| Warnings | -Wall -Wextra -Wpedantic — zero |
| Functions | Small, single-purpose |
| State | No globals. No mutable static state. |
| Macros | Almost never |
| Nesting | Three levels deep is a warning sign |
Usage: holycc [options] <input.HC>
Options:
-o <file> Output file
-c, --emit-c Emit C only (keeps .c in /tmp/)
--compile Compile to executable (default)
--run Compile and run immediately
--keep-c Keep generated .c file in /tmp/
--tokens Dump token stream
--ast Dump AST tree
--help Show this message
--version Print version
cmake --build build
./build/tests/test_lexerLexer suite: 161/161 tests passing.
Parser, semantic, and codegen test suites coming soon.
Yes, we know. We'll get there. RMS doesn't believe in deadlines anyway.
We welcome contributors. Seriously. Even if you use Emacs.
Before diving in, take 10 minutes with CONTRIBUTING.md. The short version:
- Fork & branch
- Write code — zero warnings
- Add tests for your change
- Open a PR
First time? Look for issues tagged good first issue.
We'll help you land it. Unless you use proprietary software, in which
case RMS will personally appear at your door to have a chat.
GNU General Public License v3.0
holycc — HolyC compiler for Linux
Copyright (C) 2024–2026 holycc contributors
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
See LICENSE for the full terms. See this for whatever RMS is doing today.
"Free software, free society."
— Richard M. Stallman, probably while using a ThinkPad with a freedom-compatible WiFi card that he had to source from a guy in Finland