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.

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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;

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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>.

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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;