SimpleC Compiler

Tru Bui

A compiler for a subset of the C language, written in C using Flex and Bison. Generates x86-64 assembly supporting arithmetic, pointer operations, conditionals, loops, arrays, and function calls via a register-backed stack machine.

This demo shows my Simple C Compiler (scc) compiling and.c and bubblesort.c into assembly files (.s). I then assemble them with gcc -c to produce object files, and finally link everything into runnable executables using gcc -no-pie.

Key Features

• Flex lexer + Bison parser for SimpleC grammar
• Generates x86-64 assembly compatible with gcc
• Register-backed expression stack using rbx, r10, r13, r14, r15
• Arithmetic, logical, relational, and pointer operations
• Short-circuit evaluation for && and ||
• If/else, while, for, and do-while
• Array indexing and pointer dereference
• Function calls
• Stack frame layout: saved registers, arguments, locals
• Automatic label generation for branches and loops

Implementation Details

The compiler is implemented in a single pass using Bison actions and a register-based virtual stack machine:

• Lexer (Flex): tokenizes keywords, operators, identifiers, literals
• Parser (Bison): parses grammar rules and emits x86-64 during reductions
• Expression engine: evaluates expressions using a fixed register stack and spills to memory when needed
• Control flow: lowers if/else/while/for/do-while into labels and jumps
• Function calls: implements System V calling convention and stack frame setup
• Arrays & pointers: handles a[i], *ptr, address arithmetic, and memory loads/stores
• Code output: produces fully valid .s assembly ready for linking

Contact me to see source code!