c65gm

A high-level 6502 cross-compiler targeting the ACME Cross-Assembler. c65gm provides a more expressive language for writing 6502 assembly programs, with features like functions, type-checked variables, control flow structures, and compile-time optimizations.

What It Does

c65gm compiles high-level source code into ACME assembler syntax for the 6502 processor (Commodore 64 and similar platforms). It provides:

• Type system: BYTE and WORD variables with scope resolution
• Functions: Named functions with parameters and call graph analysis
• Control flow: IF/ENDIF, WHILE/WEND, FOR loops, SWITCH/CASE
• Memory operations: PEEK/POKE/PEEKW/POKEW with zero-page optimization. Access registers as variables.
• Operators: Arithmetic (ADD, SUB), bitwise (AND, OR, XOR)
• Preprocessor: File inclusion, macros, conditional compilation, Starlark scripting
• Standard library: C64 screen/kernal routines, memory management, string handling, graphics (Koala), FAT16 filesystem, and more (accessed via #include <file>, path set by C65LIBPATH environment variable)
• Optimizations: Constant folding, self-assignment detection
• Safety features: Compile-time detection of overlapping absolute addresses in function call chains

Requirements

• Go: Version 1.25.1 or higher (tested with 1.25.5)
• Acme: Tested with release 0.97 ("Zem")

The project uses Go modules with these dependencies:

• github.com/armon/go-radix - Prefix tree for command lookup
• go.starlark.net - Embedded Starlark scripting support

Building

Build the compiler binary:

go build -o c65gm

Or install to your GOPATH:

go install

Usage

Compile a source file to ACME assembly:

./c65gm -in input.c65 -out output.asm

Then assemble the output with ACME:

acme -f cbm -o output.prg output.asm

Running Tests

Run all tests:

go test ./...

Run tests with verbose output:

go test -v ./...

Run tests for a specific package:

go test ./internal/compiler
go test ./internal/commands

Examples

See the examples/ directory for sample programs:

• hires/ - High-resolution graphics demo
• multicolorbm/ - Multicolor bitmap demo
• memlib_demo/ - Memory library usage
• switch_demo/ - SWITCH/CASE statement examples

Documentation

• language.md - Complete language reference
• syntax.md - Syntax guide
• commands.md - Command reference

License

Copyright (C) 1999, 2025 Mattias Hansson Distributed under GPL.