#16 Foundation and Architecture: Development Environment for Language Implementation -> Milestone – Development Environment Ready for Interpreter Building

This milestone marks the transition from environment preparation to actual interpreter implementation. It confirms that the foundational tools, libraries, compilers, and design scaffolding are correctly assembled to support systematic development, testing, and extension of your custom C-style interpreted language.

In the context of the latest C++ standards, this milestone reflects not only the completion of tooling setup, but also the integration of modern development principles, including modular code organization, compile-time validation, test automation, diagnostics, and IDE support. This section consolidates all previous work into a verified state, enabling confident progression into the core phases of interpreter construction: lexical analysis, parsing, semantic evaluation, and execution.

1. Confirmed Compiler and Language Support

Ensure that the toolchain has been validated for:

• C++20 and C++23 language features

  • constexpr, consteval, concepts, std::ranges, std::format, coroutines, and improved std::variant/std::optional

• Compilers configured and tested

  • GCC (13+), Clang (16+), MSVC (Visual Studio 2022+)

• Successful compilation and linking of core interpreter modules

  • Lexer

  • Parser

  • AST structures

  • Token management

  • Basic runtime shell

Checklist:

• CMakeLists.txt targets are defined and build successfully

• Compilation tested in debug and release configurations

• Compiler flags correctly enforce warnings (-Wall -Wextra -pedantic)

2. Project Structure Verified and Navigable

A consistent and modular project structure is in place. Key directories are organized with clearly scoped responsibilities:

/MyLangInterpreter/
  /src/           # Source files for interpreter logic
  /include/       # Public and private headers
  /tests/         # Unit and integration tests
  /grammar/       # ANTLR or custom grammar definitions
  /tools/         # Utilities: AST printers, symbol checkers, REPL
  /examples/      # Example programs in .lang or .test format
  /scripts/       # Build, test, deployment scripts

Checklist:

• Code navigation and IntelliSense functional in chosen IDE

• Headers are discoverable by the compiler and not duplicated

• Build system supports modular compilation (e.g., per component or per feature)

3. IDE and Editor Integration Complete

The editing environment supports efficient development through:

• Syntax highlighting for the custom language grammar

• Automatic formatting and linting for C++ interpreter code

• Real-time error diagnostics and navigation

• Integration of the Language Server Protocol (LSP) for .lang files (optional)

• Debugging support for the interpreter in C++

Checklist:

• Visual Studio Code or CLion configured with custom syntax files

• C++ LSP features enabled: Go to definition, Find references, Rename

• Breakpoints and variable watches functional during runtime evaluation

4. Core Testing Infrastructure Operational

The test framework is fully operational with unit, integration, and regression tests implemented for:

• Tokenization

• Parsing correctness

• AST construction

• Interpreter runtime shell

• Error handling and exception diagnostics

Checklist:

• Unit tests using Catch2 or doctest compile and run

• Sample programs (in .test or .lang files) pass automated evaluation

• Edge-case behavior validated (invalid syntax, divide by zero, undefined variable)

CMake test integration:

enable_testing()
add_test(NAME LexerTests COMMAND interpreter_tests --test lexer)
add_test(NAME ParserTests COMMAND interpreter_tests --test parser)
add_test(NAME RuntimeTests COMMAND interpreter_tests --test runtime)

5. Debugging and Diagnostics Functional

Core runtime features are observable and traceable:

• Internal logs for parsing, evaluation, and symbol resolution

• AST dump functionality

• Stack trace printing for runtime exceptions

• Optional DOT/Graphviz exports for AST visual debugging

Checklist:

• AST printer or visualizer integrated and produces readable output

• Internal log system toggleable (e.g., INTERPRETER_LOG_LEVEL=debug)

• Value tracing or runtime execution tracing enabled for test cases

6. Optional Tools and Enhancements Ready

Advanced tools are pre-configured for deeper testing and performance tuning:

• Static analysis via clang-tidy, clang-analyzer

• Memory validation with AddressSanitizer and Valgrind

• Performance benchmarks using std::chrono or lightweight profilers

• Integration of Godbolt (Compiler Explorer) to inspect generated code from tight evaluation loops

Checklist:

• Static analysis runs without critical errors or warnings

• Memory leak tests on runtime modules passed

• Performance-critical paths profiled and documented

7. Initial Interpreter Command-line Interface Bootstrapped

The interpreter’s initial CLI interface has been implemented and is able to:

• Read and execute .lang files

• Display errors and evaluation results

• Optionally start a basic REPL loop

• Return exit codes indicating success/failure

Example usage:

xxxxxxxxxx
./interpreter examples/hello_world.lang

int main(int argc, char* argv[]) {
    if (argc < 2) {
        start_repl();
    } else {
        run_file(argv[1]);
    }
}

Checklist:

• Program executes and returns correct results for known examples

• REPL starts without crash and accepts input

• Error output is readable and traceable to source

Final Validation: Milestone Status

Conclusion

This milestone signifies the full readiness of the development environment to begin serious interpreter construction. Every critical layer—toolchain, editor, source structure, grammar integration, testing, and debugging—is validated and functional. This foundation not only accelerates development of future chapters but also establishes a professional-grade workflow that reflects modern language implementation practices with C++20 and C++23. From this point onward, design efforts can be directed toward the interpreter core: tokenization, parsing logic, semantic validation, and code execution.