Execore

Execore is an interpreted programming language built in ISO C++23. It combines indentation-based block syntax with explicit static types (int, float, char, str, list), first-class lexical closures, and dynamic method dispatch.

The design goal was simple: get the readable feel of Python while keeping unambiguous static typing and fast, zero-allocation execution paths.

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Quick Start

Prerequisites

• Clang 19+ or GCC 15+ (ISO C++23 support required)
• CMake 3.28 or newer
• Ninja build system
• Mold or LLD linker (automatically detected)

Build and Run

# Configure and compile with Clang and Ninja
cmake --preset dev-clang
cmake --build --preset dev

# Run an example program
./build/dev-clang/execore examples/algorithms/factorial.exe

Run Tests

# Run the complete test matrix (unit, BDD, property, fuzz regression)
ctest --preset test-all

# Run under AddressSanitizer and UndefinedBehaviorSanitizer
cmake --preset asan-ubsan
cmake --build --preset asan-ubsan
ctest --preset test-asan

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Language at a Glance

1. Functions, Recursion, and Control Flow

Blocks use 4-space indentation without braces. Variables must be declared with their static type before assignment or use.

def factorial(n)
    if n <= 1
        return 1
    return n * factorial(n - 1)

int number = 6
int result = factorial(number)
print "Factorial of", number, "is:", result

2. Lists and Dynamic Sequences

Lists store dynamic values with subscripting, negative indices, and slicing.

list items
items.append(10)
items.append(20)
items.append(30)

# Slicing creates a new list with elements from index 1 up to 3
list sub = items[1:3]
print "Sublist:", sub

# Iteration over sequences
for val in items
    print "Value:", val

3. Strings and Character Conversion

Strings support sequence slicing, repetition, and builtins like ord() and chr().

str greeting = "Execore"
print greeting[0:3]       # Prints: Exe
print "-" * 15            # Prints: ---------------

char letter = 'A'
int ascii_code = ord(letter)
print "ASCII:", ascii_code, "Next:", chr(ascii_code + 1)

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Type System and Memory Layout

Type	C++ Runtime Representation	Storage Location	Key Behaviors
int	int64_t	Inline inside std::variant	64-bit signed arithmetic, bitwise operators, modulo
float	double	Inline inside std::variant	IEEE 754 double precision floating point
char	char	Inline inside std::variant	Single-byte character
str	std::shared_ptr<StringObject>	Refcounted heap object	Slicing, repetition with *, concatenation with +, .len()
list	std::shared_ptr<ListObject>	Refcounted heap object	Slicing, .append(), .insert(), .remove(), .len()
none	std::monostate	Inline inside std::variant	Default return value and null representation

Primitive types live directly inside a cacheline-friendly tagged variant. They never hit the heap during calculation or comparison.

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Pipeline Architecture

 Source File (.exe)
         │
         ▼
 ┌───────────────┐
 │ SourceManager │  Zero-copy file buffer ownership and line offset indexing
 └───────┬───────┘
         │
         ▼
 ┌───────────────┐
 │ Lexer (SoA)   │  Off-side rule indentation tracking and synthetic INDENT/DEDENT
 └───────┬───────┘
         │
         ▼
 ┌───────────────┐
 │ Parser        │  Precedence climbing with C++23 std::expected monadic results
 └───────┬───────┘
         │
         ▼
 ┌───────────────┐
 │ AST & Visitor │  Arena bump-pointer allocations and polymorphic AST hierarchy
 └───────┬───────┘
         │
         ▼
 ┌───────────────┐
 │ Semantics     │  3-tier symbol table with built-in shadowing and scope checks
 └───────┬───────┘
         │
         ▼
 ┌───────────────┐
 │ Interpreter   │  Tree-walk execution, cycle-broken lexical closures
 └───────────────┘

Key Engineering Details

• Data-Oriented Token Stream (TokenBufferSoA): Tokens can be stored as parallel contiguous vectors (kinds, spans, lexemes) instead of an array of heavy structs. This gives 100% L1 cache density during token lookahead scans.
• Monadic Error Handling: The parser provides parse_program_monadic() returning Result<std::unique_ptr<Program>, ParseError>. This wraps C++23 std::expected and chains operations with .transform() and .and_then().
• PMR Arena Allocation: MonotonicArenaResource inherits from std::pmr::memory_resource so standard library containers and AST nodes allocate from continuous monotonic memory blocks without global malloc contention.
• Deterministic Cycle Breaking: Lexical closures hold references to their parent environment. To prevent memory leaks when a function is stored inside its own environment, Interpreter tracks active environments through weak references and clears bindings explicitly on teardown.

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Performance and Benchmarks

We test performance using Google Benchmark across three microbenchmarks in benchmarks/micro/.

Run Benchmarks

# Build and run the entire benchmark suite
./benchmarks/run_benchmarks.sh

Measurements on AMD Ryzen / Linux x86_64:

• Lexer Throughput: >100 MiB/s (~4.8 Million tokens/second).
• Parser Throughput: >32 MiB/s (~870,000 expressions/second).
• Interpreter Loop Latency: ~3.4 Million loop iterations/second.

Profile-Guided Optimization (PGO)

Execore includes an automated PGO script that compiles an instrumented build, trains it on all sample workloads, merges the profile data using llvm-profdata, and links an optimized binary with ThinLTO:

./tools/scripts/pgo_build.sh

Testing the PGO release binary shows a 4x reduction in total test execution time compared to debug builds (0.71s vs 3.02s).

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5-Tier Verification Matrix

Every change to Execore passes five layers of testing:

1. Unit Tests (tests/unit/): Granular component checks for lexer, parser, value variants, and interpreter behavior.
2. BDD Scenarios (tests/unit/test_bdd_scenarios.cpp): End-to-end user workflows using GIVEN/WHEN/THEN covering off-side indentation, operator precedence binding, and recursive closures.
3. Property-Based Testing (tests/property/test_properties.cpp): 2,000 randomized property tests verifying arithmetic commutativity, associativity, string slicing round-trips, and boolean truthiness.
4. Continuous Fuzzing (tests/fuzz/): LibFuzzer harnesses for lexer and parser inputs, plus a standalone runner that executes 10,000 pseudo-random fuzzing rounds with zero crashes or leaks.
5. Mutation Testing (tests/mutation/mutation_check.py): Injects AST and operator mutations across core source files to verify that the test suite kills more than 80% of mutants.

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Command Line Usage

execore [options] <source-file>

Options:
  -h, --help             Display this help message and exit
  -v, --version          Display version information and exit
  -t, --tab-size <N>     Configure indentation tab size (default: 4)
  --dump-ast             Dump textual AST representation to stdout
  --emit-dot <file>      Export AST as a Graphviz DOT diagram to <file>
  --check-only           Perform lexical, syntax, and semantic checks without executing
  --no-color             Disable colorized diagnostic messages

Exporting an AST visualization to PNG:

./build/dev-clang/execore --emit-dot ast.dot examples/algorithms/factorial.exe
dot -Tpng ast.dot -o ast.png

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Documentation and Records

• Architecture Guide: Internal compiler pipeline, memory layout, and runtime design.
• Formal Grammar: EBNF specification for the Execore dialect.
• Architecture Decision Records (ADRs):
  • ADR 0001: Pitchfork Layout and CMakePresets v8
  • ADR 0002: C++23 Monadic Error Handling
  • ADR 0003: Arena Bump Allocator and PMR Resources
  • ADR 0004: Data-Oriented Design and Token SoA
  • ADR 0005: 5-Tier Verification and Fuzzing Matrix
• Software Bill of Materials (SBOM): CycloneDX v1.5 JSON manifest.
• Compliance Scorecard: 50/50 Frontier Tier certification.

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License

MIT License. See LICENSE for details.