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MicroC

MicroC is a statically typed subset of the language C, developed as a serie of assignments for the Languages, Compilers and Interpreters course @ UniPi.

The main simplification of this language with regards to C are:

  • Primitive data types: it supports only integers int, characters char and booleans bool;

  • Data structures: it supports only one-dimensional arrays as data structures and pointers as compound data types;

  • Heap: there is no support for dynamic allocation of memory;

  • Functions: functions can only return void, int, bool or char values;

  • There is no pointer arithmetic, there is no pointer to functions and pointers and arrays are not interchangeable;

  • There is no support for separate compilation: all the code must stay in a unique compilation unit;

Despite these simplifications, MicroC is still a Turing-complete language, so it is expressive enough to implement complex systems.

It provides two library functions to interact with the user:

  • void print(int n) // prints n to the stdout

  • int getint() // get an integer from the stdin

It also provides all types of cycles: for, do-while and, naturally, while.

There is support for the initialization of variables during the declaration and for multiple declarations. This implementation of MicroC also provides the operators for pre/post-increment ++, pre/post-decrement -- and for the abbreviate form of assignments +=, -=, *=, /=, %=. Furthermore, MicroC provides a strong(er than C) type system and a static analysis step that recognizes and eliminates dead code.

You can find a detailed description of the project and of the main design choices adopted in the official report.

Assignments Instructions

The structure of the project (i.e. the directory structure, the development environment, the starting (ambiguous) EBNF grammar, ... ) was specified from Prof. Galletta and the whole definition is available here.

The assignments required to:

  • develop the lexer using Ocamllex;

  • generate the parser using Menhir;

  • implement the concept of the symbol table;

  • define and develop the semantic analysis for the type checking and the scoping rules;

  • develop a module for the code generation for generating LLVM code;

  • implement at least three optional points chosen from a list. This implementation of MicroC provides:

    • the operators for pre/post-increment ++, pre/post-decrement -- and for the abbreviate form of assignments +=, -=, *=, /=, %=;

    • do-while loop;

    • variable declaration with initialization;

    • multiple declarations;

    • dead-code elimination;

Requirements

To build the project your system must have:

  • OCaml >= 4.12.0
  • Menhir >= 20210419
  • ppx_deriving >= 5.2
  • llvm >= 12.0.0

You can install the required dependencies via opam

$ opam install menhir ppx_deriving llvm

Usage

To build MicroC just move in the directory and run make.

Once the compiler is built, you can compile your own program using the script microcc.sh: ./microcc.sh <source_file>.

To-Do

  • arrays as pointers;
  • multi-dimensional arrays as in C;
  • seperate compilation;
  • floating point arithmetic and strings as in C, i.e. null-terminated arrays of characters;
  • structs, sizeof, bitwise and comma operators;