Blaise – A modern self-hosting zero-legacy Object Pascal compiler targeting QBE

The Pascal you love, reimagined for the modern era.

Blaise is a next-generation Object Pascal compiler built from the ground up to eliminate decades of legacy baggage. It prioritizes developer productivity, memory safety, and high-performance execution.

The Object Pascal ecosystem has two options: Embarcadero Delphi (proprietary, Windows-first) and Free Pascal (open source but carrying 30 years of accumulated complexity — five language modes, five string types, and thousands of include files).

This compiler takes a different approach:

One language mode. No {$mode} switches; no legacy dialect support.
One string type. UTF-8 reference-counted string. RawBytes for binary data.
One memory model. Automatic reference counting applies uniformly to strings, classes, and interfaces. No manual/auto split between TObject and TInterfacedObject; [Weak] breaks cycles. Free is retained as a synonym for immediate release.
Clean interfaces. No COM GUIDs; interface dispatch via compile-time vtable mapping.
Reified generics. Monomorphization at compile time — no type erasure.
Modern build system. PasBuild with project.xml; no makefiles.
First-class debugger. OPDF is the default debug format; DWARF is not required.

The result — A modern, cross-platform Object Pascal compiler targeting native code via QBE (and eventually LLVM). Single language mode, single string type, zero-GUID interfaces, reified generics, and first-class OPDF debug format support.

Self-Hosting: Yes. Blaise currently bootstraps and recompiles itself with byte-for-byte exact matches.
Testing: 1200+ tests and growing (Test-Driven Development from day one).
Backends: Currently utilizing a QBE backend, with an LLVM backend in active development.

Phase	Goal	Status
1	Bootstrap pipeline — Hello World on Linux x86_64 via PasBuild	Complete ✅
2	Type system — classes, records, ARC, exceptions	Complete ✅
3	Generics + zero-GUID interfaces	Complete ✅
4	OPDF debug info emission	Complete ✅
5	Self-hosting + LLVM + Windows + macOS ARM64	In-Progress
6	LSP + VS Code extension	Planned
7	Migration analyser for FPC/Delphi codebases	Planned

Feature	Reason for removal
`ShortString`, `AnsiString`, `WideString`, `UnicodeString`	Replaced by a single UTF-8 reference-counted `string` type
`with` statement	Source of hard-to-diagnose symbol resolution bugs; breaks static analysis
Old-style `object` types	Use `record` (stack/value) or `class` (heap/reference) instead
COM-style interface GUIDs	Interface dispatch via compile-time vtable; GUIDs are unnecessary complexity
Multiple language modes	One dialect, maintained well, beats five dialects maintained poorly
`assign`, `reset`, `rewrite`, `blockread`	Replaced by a stream-based I/O RTL
`TObject` vs `TInterfacedObject` split	One unified class model under automatic reference counting; `[Weak]` breaks cycles

The core architecture is still being finalised, so the project is not yet accepting code contributions. Feedback on language design, syntax choices, and the future direction of Blaise is very welcome — please use the Discussions tab on GitHub.

This project uses PasBuild’s multi-module layout. Each subdirectory with a project.xml is an independent module; the root project.xml is the aggregator.

project.xml                       Root aggregator (packaging=pom)
│
├── compiler/                     The compiler binary (packaging=application)
│   ├── project.xml
│   └── src/
│       ├── main/pascal/          uLexer, uParser, uAST, uCodeGenQBE, ...
│       └── test/pascal/          FPTest test suite for compiler units
│
├── rtl/                          Runtime library (packaging=library)
│   ├── project.xml
│   └── src/
│       ├── main/pascal/          System.pas, SysUtils.pas, Classes.pas, ...
│       └── test/pascal/          FPTest test suite for RTL units
│
├── tools/
│   └── migration-analyser/       FPC/Delphi migration report tool (packaging=application)
│       ├── project.xml           depends on compiler module
│       └── src/
│           ├── main/pascal/
│           └── test/pascal/
│
├── vendor/qbe/                   Vendored QBE backend source (pinned, built from source)
└── docs/                         Design documents and specifications

PasBuild compiles each module to its own target/ subdirectory. Build output is never committed to the repository.

Free Pascal Compiler 3.2.2 or later (stable; 3.3.x development snapshots are not required)
PasBuild
A C compiler (gcc or clang) for building the vendored QBE backend
GNU ld or lld (Linux); ld (macOS)

PasBuild resolves the module dependency order automatically and compiles rtl → compiler → tools/migration-analyser.

pasbuild compile -p debug      # includes -g -gl -Criot -gh
pasbuild compile -p release    # includes -O2 -CX -XX -Xs

pasbuild compile -m blaise-compiler

Once built, the compiler binary is at compiler/target/blaise.

# Compile a single file
compiler/target/blaise --source Hello.pas --output Hello

# Compile via project.xml
compiler/target/blaise --project project.xml --config debug --output myapp

# Emit QBE IR (useful for debugging the compiler itself)
compiler/target/blaise --source Hello.pas --emit-ir

Apache License v2.0 with Runtime Library Exception. See LICENSE.

Built with ❤️ for the Pascal community by Graeme.

What Is Dropped From Classic Pascal