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Gambit Compiler with React-based VM State replay
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README.md

The Gambit Language

This is a for-educational-purposes only programming language, compiler, and virtual machine.

How to build this project

This project requires both a C (for extensions) and C++ compiler. By default it was tested on GCC v8.1.0, clang version 4.0.0, and g++ with modifications to the makefile parameters. sed is also utilized to resolve and compile dependencies.

This project depends on bison v3.0.4 and flex v2.5.37. I can't guarantee it'll work on other versions, so they are included in the util package. Compile these two projects and update build/gambit.mk to point to their executables. You will also need to update the following line in the Makefile to include the header within util/flex as opposed to your system headers. You do not need to install these on your system, but the executables to generate the grammar files are needed.

INC         := -I$(INCDIR) -Isrc -Isrc/test -I$(LIBDIR) -I$(EXTDIR) -I/usr/local/opt/flex/include

Within the build directory, there is a bash file that will run various make commands to setup the mate compiler and its dependencies.

What has this been tested on?

Mac, Ubuntu, CentOS.

Will this work on Windows?

Possibly. If you utilize clang v4.0 with C++ installed, set your PATH to include mingw-w64, and have gnuwin32 on your system: you might be able to get Mate to compile. Due to different versions of Flex, Bision, and Sed, it is unlikely.

Mate utilizes two external libraries, args.hxx for argument parsing, and debugnew for memory debugging. These both port over to Windows without an issue.

Porting to Windows may come in the future.

Gambit

Gambit is a strongly-typed, object-based, programming language. Not much has been implemented in the language as of yet.

# integers
10
12

# strings
"Benjamin Anderson"

# assignment
Integer::my_age = 24

#get locals
my_age


# methods (in current scope)
String::my_name = "Benjamin Anderson"

puts(my_name)

# method definitions
@echo -> Void
{
 puts("asdf")
}


@print_and_return -> String::a -> String::b -> String
{
  puts(a)
  puts(b)
  => a
}

Board

Board is an in-memory log and VM state capture system that allows you to visualize the state of the RookVM. It can be utilized for debugging memory, bugs in the VM/instruction set, or for educational purposes.

check handler error

Check

Check is a human-readable error handler. Though optimized for the Mate compiler, it is a shared library that can be utilized for any C++ project. Features of Check are still being implemented and error messages continue to be improved upon.

check handler error

Handling Errors with Check

Check provides a simple interface for when you throw errors in your application. With Check, you have to wrap your application in a try - catch block in order to handle errors properly. Your errors must also implement the iException interface.

class AssignDataTypeMismatch : public iException
{
	// ...
	const char * what () const throw ()
	{
		this->check->load(ASSIGN_DATATYPE_MISMATCH);
		std::vector<std::string> p;		
		p.push_back("ASSIGNMENT DATATYPE MISMATCH");
		
		return this->check->getFactory()->create()->with(p)->emit().c_str();
	};
}

try
{
	// some errorous code
	throw AssignDataTypeMismatch();
}
catch(Exception::iException &e)
{
	std::cout << e.what() << std::endl;
}

Mate

An extensible compiler that accepts a language driver containing a parsed AST. Mate emits Pawn bytecode.

Basic Usage

Mate has the following flags:

-h displays the help meny
-c[filename] compile a file
-o[outfile] output filename of pawn bytecode

Example: matec -c test.gbt -o test.pwn

Extending Mate / Gambit

Mate provides a simple interface for creating extensions. Mate uses dlfcn for extensions, so you can utilize both C and C++. This is still under development. A generic Make file will be provided once the interface is finalized. Macros will also be defined.

The following headers are required to create an extension (with methods) in Mate:

#include "shared/runtime/iStandardClass.hpp"
#include "shared/runtime/iMethod.hpp"

The extension signature has a create definition and destroy definition:

extern "C" Runtime::iStandardClass* create(Runtime::iStandardClass* runtime)
{
  return runtime;
}

extern "C" void destroy(Runtime::iStandardClass* runtime)
{
	// mate will delete your object passed to the runtime.
	// ensure your destructor is virtual to do needed cleanup
	// use destroy to add some debugging, local variable deleting, etc.
}

Adding Objects to the Runtime

When creating an extension, using native C++ classes that extend Runtime::iStandardClass is the easiest approach.

namespace Runtime
{

  class Sqlite : public Runtime::iStandardClass
  {

    private:
      sqlite3 *db;
      int rc;

    public:

      using Runtime::iStandardClass::iStandardClass;

      virtual ~Sqlite()
      {
        std::cout << "deleting sqlite" << std::endl;
      };

  };
}

#define SQLITE_CLASS_NAME "Sqlite"

extern "C" Runtime::iStandardClass* create(Runtime::iStandardClass* obj)
{
  Runtime::Sqlite *sqliteExt = new Runtime::Sqlite(SQLITE_CLASS_NAME);
 
  // Sqlite class inherits from Object in our runtime
  sqliteExt->setSuperClass(obj);

  // register our class in the runtime
  obj->setConstant(SQLITE_CLASS_NAME, sqliteExt);

  return sqliteExt;
}

Adding Methods

Methods are also objects. The method interface is currently incomplete, Mate does not yet recognize data types for method parameters and return types. You can, however, currently add methods and execute them within the C++ environment.

namespace Runtime
{

  // .. previous code

  class SqliteInitializeMethod : public Runtime::iMethod
  {

    public:

      SqliteInitializeMethod()
      {
        // parameter datatypes
        PARAMETER_TYPE("String")
        PARAMETER_TYPE("Integer");
      };

      virtual Runtime::iStandardClass* call(Runtime::iStandardClass *receiver, std::vector<Runtime::iStandardClass*> arguments)
      {
        std::cout << "called initialize" << std::endl;
        return receiver;
      };

  };
}

extern "C" Runtime::iStandardClass* create(Runtime::iStandardClass* obj)
{
  Runtime::Sqlite *sqliteExt = new Runtime::Sqlite("Sqlite");

  sqliteExt->setSuperClass(obj);

  // bind native method to runtime "initialize" on sqlite object
  sqliteExt->addMethod("initialize", (new Runtime::SqliteInitializeMethod()));

  obj->setConstant("Sqlite", sqliteExt);

  return sqliteExt;
}

Pawn

The bytecode output by the Mate Compiler.

OP Code Operand 1 Operand 2 Operand 3 Operand 4 Description
NOOP No operation
PUSH_INTEGER Integer Obj Pushes an Integer onto the Stack
PUSH_STRING String Obj Pushes a String onto the Stack
PUSH_ARRAY Array Size n Pops n elements from the Stack and pushes an array
SET_LOCAL Class Identifier Pops top element on the Stack, sets local variable in current frame
PUSH_SELF Pushes the current object context onto the stack
CALL String MethodSignature Args Count Executes a method. Pushes result to stack. Void types are popped from the stack immediately
GET_LOCAL < *&>LiteralOffset Gets local from current scope. ByReference or Value
RETURN Bool PopStack Exits current frame. Operand 1 tells the VM whether or not to return a value
POP Pops top element from the Stack

The following are operators that can be appended to operands to modify the state/behavior of the virtual machine.

Operator Description
Default behavior of instruction
* By Value - Clone
& By Reference - Pointer

Pawn to Assembler

Pawns instructions are slowly being optimized to have a 1 ~ 2 or 3 corrospondence to Assembler. The Rook VM does many assumptions for us, for example, for each method and the initial .code block, Rook does the following:

// create a new frame and push it onto the stack
VM::iFrame* f = new VM::iFrame("frame identifier");
this->cg->getFrameStack()->pushFrame(f);

Whereas in Assembler, we have to explicitly state we are pushing up the base pointer

  pushl   %ebp
  movl    %esp,   %ebp

So each code and method label would have to begin with the above.

Pawn, like assembler, has a return statement at the end of each method and code block. Pawn, however, has an operand that states if the return value will be pushed to the parent frame/stack. Assembler moves the return value into eax / rax.

.code
// pawn bytecode
PUSH_INTEGER	10
RETURN 1

Would be the ASM equivelent

.start
  pushl   %ebp
  movl    %esp,   %ebp
  pushl	$10
  popl    %eax
  movl    %ebp,   %esp
  popl    %ebp
  ret						; 10 is in eax

The RookVM Doesn't Care

The RookVM doesn't care about data types, it will call any function in its bytecode ie:

PUSH_INTEGER 10
CALL Object_puts_String

Even if the datatype on the stack would be incorrect. That is why we have the Mate Compiler to handle this for us.

Literals Section is Just Data

The literals section in the Pawn Bytecode. C++ can easily load parsed text into memory, ASM needs a few extra steps

; pawn bytecode
; .literals
;	"this is a string"
; needs to translate to

.section data
	s_01: .ascii "this is a string\0"

; whenever it's used, you need to get the length
.start
	; frame pushing etc inferred
	pushl	$s_01
	call	str_len
	; eax now has the string length

The issue with locals

Due to the nature of the Gambit Runtime, locals are not offset-based; but rather identifier-offset based. The RookVM still tracks identifiers, which is simple for VM reasons, but not practical in an ASM environment. The solution would be to add identifier offset tracking on a frame-basis.

Where are the unit tests?

Test first, or you'll never write tests. That is the case with this project, except this is strictly a proof-of-concept as opposed to me actually wanting to build something to be taken seriously. It's for my and others learning purposes. Eventually I'll rewrite the entire project with tests (with catch.h) from the start as there is an end goal with the POC. Yes, a compiler and virtual machine require a lot of code to not consider writing tests from the start, but I'm patient.

License

MIT - For educational purposes only.

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