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LPC - An experimental "Standard Pascal" (ISO 7185) Compiler

LPC is a simple Pascal compiler, primarly intended as a sandbox to experiment with compiler construction ideas. It grew from a toy compiler for a small subset of Pascal (originally generating 80206 assembly, although the code for that backend is now lost)

Currently it supports the core ISO 7185 features and it generate C++ code or MSIL (CIL) assembly targeting .NET CLR.

It was never meant to be a production compiler, and the design decissions reflect that. It's not an "optimizing compiler" either. Instead, the main goals are:

  • A simple and clean architecture
  • Explicit grammar specification (Lex/Yacc style lexer and parser)
  • Intuitive data structures (AST, symbol table and type system)
  • Clear separation between the front end and the backend (using an AST visitor interface)
  • Small language support runtime
  • Reasonably clean code generation (human readable and preserving the structure of the original Pascal code as much as possible)

Prerequisites

  • Visual C++ 2017 or later (the Community edition should suffice)
  • Flex++/Bison++. Must be added to the PATH.
  • Python 3 (needed to run the tests)

Building and running LPC

Important: Flex++ may require a small manual patch. If the build complains about a missing osfcn.h header, comment out or remove the corresponding #include <osfcn.h> from the flexskel.cc file (located next to the flex++.exe binary)

  1. Load lpc.sln in Visual Studio, then build (ex. Build/Build Solution)
  2. lpc.exe is the executable (by default located in the Debug or Release subdirectory)
  3. The lpc.exe has a very simple command line interface: lpc [options...] <inputFile>
  4. Run lpc -? for the list of options

Running the tests

The tests are under the test directory (Python3 is required to run the tests)

  1. Setup the Visual C++ command line environment

    • Option 1: From the IDE, use "Tools / Visual Studio Command Prompt"
    • Option 2: Run vcvarsall.bat from a command line window

  2. Execute runTests.py from the test directory

    The build flavor (debug/release) and the code generation target must be selected (currently cpp or clr). For example:

    python runtest.py debug clr

Resources

A special thank you to Scott A. Moore, the creator of standardpascal.org for maintaining one of the best collection of materials about ISO 7185 (Standard Pascal).

This is not an officially supported Google product