To get an understanding of the internals please read this
overview and start digging around in the code. If you want to
get involved you should read the language
specification and
start writing small Monty programs to get to know the language.
If you've done that you may start fixing some bugs you might have encountered or refer to the implemented features list.
Please refer to the README for instructions on how to build the project. Of course you'll need maven and the JDK installed. The basic commands you need to know are:
| Command | Description |
|---|---|
mvn compile |
Build the java sources and run the formatter. |
mvn test |
Run mvn compile and the test suite. |
mvn package |
Run mvn test and build an executable jar. |
This project uses the java-formatter-plugin with rules defined in
src/main/resources/moco-code-conv.xml. Please import these into your IDE or
run mvn compile before contributing code to format your changes accordingly.
If you want to submit to the moco code base please use the Github merge request feature. Please make sure to have atomic commits and well formed commit messages. Please also ensure to only commit necessary changes, that the tests still pass and the jar is executable and that you used the formatter and stripped trailing whitespaces.
Your request will be merged, if at least two project members singed off your proposal and none vetoed.
This project builds on top a few libraries, managed by maven. These are:
| Library | Description |
|---|---|
| ANTLR4 | See parser generator. |
| Argparse4j | Used for parsing the command line arguments. |
| Apache Commons: IO, Lang | Used in the code generation and for files IO. |
| JUnit, Mockito, Hamcrest | Used for the unit- and integration-Tests. |
ANTLR4 is a parser generator that builds the parser
for the Monty syntax using the syntax grammar
(de.uni.bremen.monty.moco.antlr.Monty.g4) and some lexer rules
(src/main/antlr4/imports/lex.g4) at compile time. The generated parser
(de.uni.bremen.monty.moco.antlr.MontyParser.java) is used within
de.uni.bremen.monty.moco.ast.AntlrAdapter.java to build the parse tree. This
parse tree is simplified using de.uni.bremen.monty.moco.ast.ASTBuilder.java
to an abstract syntax tree using classes from the package
de.uni.bremen.monty.moco.ast.
To traverse the abstract syntax tree generated by
de.uni.bremen.monty.moco.ast.ASTBuilder.java the compiler uses the visitor
design pattern. Every visitor traverses the entire abstract syntax tree and
performs various tasks. These are the visitors in the order in which they run.
| Visitor | Description |
|---|---|
SetParentVisitor.java |
Set the parent node for each node. This is necessary for some operations later. |
DeclarationVisitor.java |
Set up the scopes and declare every type and variable in the right one. |
ResolveVisitor.java |
Resolve every Identifier for the associated declaration. |
TypeCheckVisitor.java |
Check for type safety. |
ControlFlowVisitor.java |
Check for correct control flow. e.g. if a function has a return in every branch. |
NameManglingVisitor.java |
Mangle every Identifier for LLVM to manage scopes and reserved LLVM chars. |
CodeGenerationVisitor.java |
Generate the LLVM-IR using support classes. See here. |
The visitors implement a visit(*) method for each node type and use a
technique called double dispatch to ensure that the right visit() method was
called. Please use the comfort method visitDoubleDispatched(ASTNode) within
a visitor.
The de.uni.bremen.monty.moco.visitor.CodeGenerationVisitor.java visits the
abstract syntax tree and generates the LLVM-IR using classes from the
de.uni.bremen.monty.moco.codegeneration package. Some classes in particular
are interesting:
| Class | Description |
|---|---|
..codegeneration.CodeGenerator.java |
Complex methods to generate code using the CodeConext. e.g. calling a function. |
..codegeneration.context.CodeContext.java |
Low level LLVM equivalent methods. |
..codegeneration.types.TypeConverter.java |
Maps a ClassDeclaration to a LLVM type. |
..codegeneration.types.LLVMTypeFactory.java |
Utility functions for type creation and conversion. |
..codegeneration.identifier.LLVMIdentifierFactory.java |
Utility functions for identifier creation and conversion. |
..codegeneration.voodoo.BlackMagic.java |
Generate the body for built-in methods. |