uc80 0.4.0

ANSI C compiler targeting Z80/CP/M

uc80 - ANSI C Compiler for Z80

A C compiler targeting the Z80 processor and CP/M operating system. Produces assembly compatible with the um80 assembler and linker toolchain.

Installation

pip install uc80

Or from source:

pip install -e .

Requires the um80 assembler/linker toolchain:

pip install um80

Quick Start

# Compile, assemble, and link a C program
uc80 hello.c -o hello.mac
um80 hello.mac -o hello.rel
ul80 hello.rel lib/libc.lib lib/runtime.lib -o hello.com

Best Optimization (Whole-Program)

For smallest binaries, compile all .c files in a single invocation. This enables whole-program optimizations that are not possible when compiling files separately:

# Single-file (best optimization - all optimizations enabled by default)
uc80 main.c utils.c -o program.mac
um80 program.mac -o program.rel
ul80 program.rel lib/libc.lib lib/runtime.lib -o program.com

Default optimizations (all enabled unless disabled):

• Whole-program mode: Dead function elimination across all files
• Shared storage: Non-recursive functions use static allocation instead of stack frames
• Function inlining: Small functions expanded at call sites
• Constant propagation: Interprocedural constant folding
• AST optimization: Expression simplification, strength reduction
• Assembly DCE: Dead code elimination at assembly level
• Peephole optimization: Pattern-based instruction replacement
• Printf auto-detection: Scans format strings to link only needed handlers; rewrites printf("...\n") to puts("...") when no format specifiers are used
• Embedded runtime: Runtime functions included as source, DCE removes unused ones

Printf Control

The compiler auto-detects which printf format specifiers your program uses and links only the needed handlers. You can also control this explicitly:

# Command line
uc80 program.c --printf int           # %d %u %x %o %s %c %p only
uc80 program.c --printf int --printf long  # add %ld %lu %lx
uc80 program.c --printf float         # add %f

# In source code
#pragma printf int
#pragma printf long

Configurable Integer Sizes

By default int is 16 bits (natural Z80 word width). Code that assumes 32-bit int can be compiled with a CLI override — no source changes:

uc80 program.c --int=32 -o program.mac     # 32-bit int
uc80 program.c --long=64 -o program.mac    # 64-bit long

The bundled headers (<limits.h>, <stdint.h>, <stddef.h>, <inttypes.h>) derive their typedefs and limit macros from compiler-supplied __SIZEOF_*__ and __*_MAX__ macros, so the same header files work under every config. Codegen routes arithmetic, printf/scanf format dispatch, and sizeof through the selected widths automatically.

Separate Compilation

When compiling files separately for separate linking, use --no-whole-program:

uc80 --no-whole-program module.c -o module.mac

Binary Size

uc80 produces the smallest known binaries for Z80/CP/M among current compilers.

Tested against z88dk (SDCC backend, -SO3 --max-allocs-per-node10000) on the Fujitsu compiler-test-suite:

Metric	Result
uc80 smaller	47/47 tests (100%)
Aggregate size ratio	46% (uc80 is less than half the size)
Total uc80	170,496 bytes
Total z88dk	369,644 bytes
Minimal binary	128 bytes (vs 5,172 for z88dk)

Sample sizes (bytes):

Program	uc80	z88dk	Ratio
hello world (puts)	256	5,172	5%
printf %d	4,608	7,696	60%
integer math	5,248	7,948	66%
long arithmetic	5,632	7,793	72%

Test Results

Tested against multiple external test suites:

Suite	Pass Rate	Notes
c-testsuite	220/220	full pass
c-testsuite --int=32	219/220	00200 (long-long shift) overflows 64K TPA
c-testsuite --int=32 --long=64	218/220	same as above + marginal timeout
Fujitsu compiler-test-suite 0003	371/374
Fujitsu 0010	58/75	9 int16, 1 float, 2 timeout
Fujitsu 0011	287/335	14 int16, 5 large struct
Fujitsu 0012	4/9	4 int16/long long, 1 static DCE
SDCC regression tests	514/523	3 fail, 4 sdcc ext, 2 multi-file link

Remaining non-passing tests are environmental, not codegen bugs:

• sdcc ext: SDCC-specific extensions (__asm, #pragma save/restore)
• multi-file: tests that require separate compilation units
• float precision: ACOSF/TANF near asymptotes (single-precision IEEE 754 limit)
• malloc OOM: SDCC test asserts malloc(2000) == NULL; we have plenty of TPA
• 00200: 67KB binary exceeds 64KB CP/M TPA

Features

• ANSI C (C11/C23) with most standard features
• Z80 code generation with peephole optimization
• IEEE 754 single-precision float
• Configurable integer sizes (--int=16|32, --long=32|64); default is 16-bit int, 32-bit long, 64-bit long long
• Structs, unions, bitfields, enums
• Full preprocessor (#include, #define, #if, #pragma, etc.)
• Modular library with selective linking
• Whole-program optimization
• CP/M target with embedded crt0

Related Projects

• 80un - Unpacker for CP/M compression and archive formats (LBR, ARC, squeeze, crunch, CrLZH)
• cpmdroid - Z80/CP/M emulator for Android with RomWBW HBIOS compatibility and VT100 terminal
• cpmemu - CP/M 2.2 emulator with Z80/8080 CPU emulation and BDOS/BIOS translation to Unix filesystem
• ioscpm - Z80/CP/M emulator for iOS and macOS with RomWBW HBIOS compatibility
• learn-ada-z80 - Ada programming examples for the uada80 compiler targeting Z80/CP/M
• mbasic - Modern MBASIC 5.21 Interpreter & Compilers
• mbasic2025 - MBASIC 5.21 source code reconstruction - byte-for-byte match with original binary
• mbasicc - C++ implementation of MBASIC 5.21
• mbasicc_web - WebAssembly MBASIC 5.21
• mpm2 - MP/M II multi-user CP/M emulator with SSH terminal access and SFTP file transfer
• romwbw_emu - Hardware-level Z80 emulator for RomWBW with 512KB ROM + 512KB RAM banking and HBIOS support
• scelbal - SCELBAL BASIC interpreter - 8008 to 8080 translation
• uada80 - Ada compiler targeting Z80 processor and CP/M 2.2 operating system
• uc386 - C23 compiler targeting Intel 386 (x86-32) and MS-DOS; sibling backend sharing the uc_core frontend
• uc_core - Shared C23 frontend and AST optimizer used by uc80 and uc386
• ucow - Unix/Linux Cowgol to Z80 compiler
• um80_and_friends - Microsoft MACRO-80 compatible toolchain for Linux: assembler, linker, librarian, disassembler
• upeepz80 - Z80 peephole optimizer
• uplm80 - PL/M-80 compiler targeting Intel 8080 and Zilog Z80 assembly language
• z80cpmw - Z80 CP/M emulator for Windows (RomWBW)

License

GPL-3.0-or-later. See LICENSE.