cluck

A compiler for a subset of C written in Haskell.

Inspired by MicroC

Generates LLVM IR, uses Clang as a backend.

Features

• Variable and function declarations
• Return, if, for, while, do-while and switch statements
• Expressions and precedence
• Number, char and float literals
• Binary and unary operators (most implemented)
• Detailed syntax errors
• Static analysis for bindings and types
• Code generation for expressions and functions
• Pointer types
• Type casts
• Arrays (1-dimensional)

Built-in functions (no includes required):

void* malloc(int);
void free(void*);
int scanf(char*, void*);
int printf(char*, ...);
double sqrt(double);
double pow(double, double);

Differences with C

Although Cluck implements a language extremely similar to C, there are a few notable language differences:

• there is no preprocessor, the built-in functions are implicitly imported into every program
• float is implemented as a double underneath, this means %lf must be used in format strings
• bool is implemented as a primitive type
• switch statements have implicit fallthrough and there is no default case
• arrays decay in the scope they are defined in to a single pointer, this means that sizeof does not work as expected
• arrays cannot be defined in more than 1 dimension
• there is no implicit casting with literal expressions, so if the value 0 wants to be used in a float expression then it must be initialised as '0.0' or casted explicitly

Resources used

C89 Draft

Writing a C Compiler - Nora Sandler

Functional Parsing - Computerphile

Megaparsec tutorial

Compiling a functional language to LLVM - Daniel J. Harvey

Micro C - Joseph Morag

Godbolt Compiler Explorer

Usage

Only compatible with GHC 8.8.

Requires LLVM 14 to be installed including Clang 14.

On Ubuntu:

sudo apt install clang-14

ghcup install cabal

cabal build

Binary is located in ./dist-newstyle/build

./cluck <input file>.c

If no input file is provided, code can be entered directly via standard input.

Use Ctrl + D to submit once typed.

Options

-o - Specify output file

-A - Output AST

-H - Generate header file

-S - Output LLVM IR

--help - Output help page

Examples

The examples folder contains some supported programs used to test the compiler's capabilities.

Example	Description
primes.c	An implementation of the Sieve of Eratosthenes algorithm.
merge.c	An implementation of Merge sort.
trig.c	The sin, cos and tan functions approximated using the Maclaurin Series.