MALBR

MALBR — Micro ALB Rust — is the second compiler in the AdaLogic BASIC toolchain, and the path by which ALB reaches machines its reference compiler cannot. Where albt is a complete, batteries-included compiler that assembles FASM directly and serves the retro backends, MALBR is deliberately small: it translates ALB source into clean, deterministic #![no_std] Rust and hands the result to rustc, which brings cross-compilation to dozens of targets, a mature optimizer, bare-metal support, and an enormous linker ecosystem. MALBR does not try to be smarter than rustc — it emits predictable code and lets the backend machinery do what it was built to do.

Its sibling is MALB: the same ALB→Rust compiler written in ALB itself, roughly 3,900 lines of it, compiled first by MALBR and then by itself — proven self-hosting through a byte-identical bootstrap fixpoint. Together they move ALB toward a two-flagship toolchain: albt as the reference compiler, and the MALBR/MALB pair as the road to embedded targets, foreign operating systems, and a compiler maintained in the language it compiles.

Why a second compiler

albt knows the whole language — the full builtin set, the special blocks, the sixteen targets from native x86-64 down to 6502 assembly. What it cannot easily do is reach the places ALB increasingly wants to go: small boards, embedded targets, toolchains the project does not own. A FASM-centric pipeline cannot piggyback on someone else's backend ecosystem.

MALBR was created to fix exactly that gap. Rust already solves cross-compilation, optimization, and no_std bare-metal deployment — so MALBR emits Rust source rather than machine code, keeping itself small and auditable while inheriting everything rustc knows about target triples, linking, and code generation. The trade is explicit: one more language in the pipeline, in exchange for the widest backend reach a modern toolchain offers.

What the output looks like

Every MALBR program compiles to a crate with a fixed shape:

The program body lands in fn _alb_main_body(), behind a #[no_mangle] pub extern "C" fn main() that calls it and exits through support::_alb_exit(0). File-scope LET declarations become static mut with unsafe access; routine-local LETs stay ordinary let muts. String handling runs through a static arena — 64 KiB by default, resizable with --arena <bytes> — with CLAIM, SWEEP, and DROP as checkpoint/rewind/release controls. There is no heap and no crates.io dependency: the binary can be audited byte-for-byte and flashed directly.

Fault codes — one trap door

Every runtime trap in generated code funnels into a single function, support::_alb_fault(code) — the override point embedded ports replace:

A bare-metal port can hang, log over UART, or blink an LED on any of these — the generated code never decides the policy.

The support ABI — porting is six functions

MALBR's runtime boundary is support.rs, a three-file facade:

To take ALB to a new board you replace tier 1 — roughly six functions — and optionally tier 2 for environment services. Generated code only ever talks to support::_alb_*, so a port never touches emitted source. This is the same strategy small language ports have used since the early byte-code machines: separate what the program means from what the machine can do.

Semantics are the spec

MALBR's contract is behavioral, not structural. The test suite diffs real program output — a semantic drift is a test failure, not a shrug. The details it guarantees are the ones a user would notice:

• | stays string concatenation (and & its alias); bitwise work uses

AND/OR/XOR keywords, ^ is exponentiation

• NOT keeps classic-BASIC precedence — looser than comparisons, tighter

than AND; NOT x = 5 means NOT (x = 5)

• AND/OR never short-circuit; ANDALSO/ORELSE do
• PRINT truncates floats to six decimals — display only, not the value
• READ(h, 0) reads the rest of the file; both ELSEIF and ELSIF parse
• reserved words error with line/column instead of cascading parse failures

Float math without a standard library

#![no_std] means no libm, so MALBR carries its own: Cody–Waite argument reduction plus minimax polynomials give sin, cos, atan, exp, and ln to about 1 ulp, with tan, asin, acos, atan2, and pow in the 2–3 ulp range. floor, ceil, trunc, round, and sqrt are integer casts with Newton fixups — the core intrinsics would pull in std. For an embedded BASIC, that is an unusually serious numerics story: see Scientific notation and History of Mathematics for why floating point conventions mattered enough to standardize.

MALB — ALB written in ALB

Once MALBR could compile real programs, one question became inevitable: can ALB compile its own compiler? MALB (MALBR_BS/malb.alb, about 3,900 lines) is the answer — a complete ALB→Rust compiler written in the language it compiles. The self-hosting claim is proven the hard way, not asserted:

  malbr.exe  builds  malb.exe                       (stage 1 — Ada backend)
  malb.exe   compiles malb.alb -> malb2.rs          (stage 2)
  malb2.exe  compiles malb.alb -> malb3.rs          (stage 3)

  malb2.rs == malb3.rs    — identical, byte for byte

When a compiler's own 3,900-line source is the test program and the stage-2 and stage-3 outputs agree exactly, "almost right" has nowhere to hide. This is the same fixpoint argument classic self-hosting compilers — from Pascal's P-system to GCC's three-stage build — have used to demonstrate correctness; see Compilers for the tradition.

Coverage and status

MALB currently passes 209 of 209 output-verified fixtures — emit → rustc → run → diff — including MD5, FFT, Jaro–Winkler, N-queens, maze generation, FFI calls into kernel32, and the semantics regression tests (short-circuit behavior, NOT precedence, checked overflow, contracts). The language coverage is full: modules and INCLUDE, contracts (REQUIRE/ENSURE/OLD), structs, enums, bitfields, range types, routine references and REF, floats, multi-dimensional arrays, SELECT, ENABLE RUST, and the complete builtin set.

The CLI is deliberately boring. MALB is in early access; the roadmap's priorities are performance of the self-built binary, --map-style audit output, and then the point of the exercise — malbr.adb freezing forever as the bootstrap compiler, with ALB's compiler maintained in ALB from that day forward.

Where it sits in the toolchain

See also

• AdaLogic BASIC — the language these compilers serve
• ALB Ada backend — sibling backend in the same Ada toolchain
• ALB FASM backend — the workhorse native x86-64 target
• Rust — the language MALBR emits
• Ada Programming Language — the language both albt and malbr are written in
• Compilers — self-hosting and bootstrap traditions
• Forth — another language that took tiny, auditable toolchains to telescopes and space probes

References

1. "Update: MALBR and MALB — a second compiler, and ALB written in ALB," ALB repository, docs/updates/2026-10-malbr-malb-announcement.md (October 2026).
2. MALBR Dialect Specification — Micro ALB, ALB repository, docs/MALBR_SPEC.md — the normative dialect contract.
3. MALBR Internals — what the generated Rust actually looks like, docs/MALBR_INTERNALS.md.
4. MALBR Porting Guide — taking ALB to a new target, docs/MALBR_PORTING.md.
5. MALBR ABI, docs/MALBR_ABI.md — the support.rs two-tier contract.
6. MALBR Roadmap — Micro ALB compiler → production, docs/MALBR_ROADMAP.md.
7. ALB source — github.com/rockyoliver454/AdaLogic-BASIC-ALB-Programming-Language — Apache 2.0, including src/malbr.adb, src/EMITTER/emit_native_micro_rust.adb, and MALBR_BS/malb.alb.
8. ALB Handbook — alb-lang.org/handbook — the language reference shared by every backend.

Quiz — MALBR and MALB

• What does "MALBR" stand for, and what language does it emit?
• Why does ALB need a second compiler when albt already targets sixteen backends?
• What two attributes appear at the top of every MALBR-generated crate?
• How large is MALBR's default string arena, and which flag resizes it?
• Name the function every runtime trap routes through, and give three fault codes.
• How many functions does a minimal MALBR board port require, and in which file do they live?
• In ALB, what does | mean — and how does MALBR treat it in generated Rust?
• Which ALB keywords provide short-circuit logic, since AND/OR do not?
• Approximately how accurate are MALBR's sin/cos/exp/ln implementations?
• What is MALB, and roughly how many lines of ALB is it?
• Describe the three stages of the MALB bootstrap and what equality proves.
• How many output-verified fixtures does MALB currently pass?