System Software & Compiler Design — Lab Programs

This repository contains lab exercises and assessments for a System Software & Compiler Design (SSCD) course. The exercises use Flex (lex) and Bison (yacc) to build scanners and parsers, demonstrated on Windows using MSYS2 / UCRT64 toolchains.

Table of Contents

• Overview
• Tech Stack
• Setup (MSYS2 UCRT64)
• Compilation Workflow (Flex → Bison → GCC)
• Lab Programs (files)
• Usage Examples
• Assessment Notes
• Contributing & Roadmap

Overview

• Purpose: Hands-on lab programs demonstrating lexical analysis (Flex) and syntax analysis (Bison) for typical compiler-construction tasks: tokenization, expression evaluation, grammar validation, comment stripping, and token counting.
• Contents: A set of .l (Flex) and .y (Bison) source files, alongside some generated *.tab.c, *.tab.h, and lex.yy.c artifacts from previous builds.

Tech Stack

• Lex / Flex: tokenizers written in .l files.
• Bison / Yacc: parsers written in .y files.
• GCC: building and linking generated C code.
• Platform: Windows with MSYS2 (UCRT64) recommended; works similarly on Linux/macOS with package-equivalents.

Setup (MSYS2 UCRT64)

1. Install MSYS2 from https://www.msys2.org/ and open the UCRT64 shell.
2. Update package database and core packages:

pacman -Syu

3. Install required development packages:

pacman -S mingw-w64-ucrt-x86_64-gcc mingw-w64-ucrt-x86_64-flex mingw-w64-ucrt-x86_64-bison make

4. From the UCRT64 shell, change to the repository folder:

cd /c/Users/ajith/Videos/nano_test/SSCD\ lab

Compilation Workflow (Flex → Bison → GCC)

• Typical steps:

# 1. Run Flex on the .l file (generates lex.yy.c)
flex p2.l

# 2. Run Bison on the .y file (generates parser files and header)
bison -d p2.y    # produces p2.tab.c and p2.tab.h

# 3. Compile and link with GCC
gcc p2.tab.c lex.yy.c -o p2 -lfl

# 4. Run the program
./p2

• On MSYS2 UCRT64, you may need to use the mingw-w64 prefix if compiling for native Windows executables:

mingw32-make # or use gcc from mingw toolchain explicitly
gcc p2.tab.c lex.yy.c -o p2.exe -lfl

Diagram: compilation workflow

flowchart LR
	A[Flex: .l file] --> B[lex.yy.c]
	C[Bison: .y file] --> D[p2.tab.c + p2.tab.h]
	B & D --> E[GCC link]
	E --> F[Executable]

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Lab Programs (Files & Descriptions)

• p1.l (p1.l: checks arithmetic expression validity and counts operands/operators; validates parentheses balance and prints recognized operands and operators.)
• p2.l (p2.l: tokenizes integers and arithmetic symbols; provides NUM tokens to the parser.)
• p2.y (p2.y: Bison grammar to parse and evaluate arithmetic expressions with + - * / and parentheses; prints computed result.)
• p3.l (p3.l: simple lexer mapping characters a and b into tokens A and B, plus newline handling.)
• p3.y (p3.y: grammar validating strings over A and B (productions: S -> A S | B) and reports "Valid String" on success.)
• p4.l (p4.l: comment stripper — counts comment lines (// and /* ... */) and writes non-comment text to an output file.)
• p5.l (p5.l: lexical analyzer printing tokens (operators, digits, keywords, identifiers) and returning token categories to parser.)
• p5.y (p5.y: parser that counts occurrences of digits, identifiers, keywords, and operators by driving the analyzer over p5_input.c.)

Generated and present artifacts (from previous builds):

• lex.yy.c — generated scanner (exists in repository)
• p2.tab.c, p2.tab.h, p3.tab.c, p3.tab.h, p5.tab.c, p5.tab.h — generated parser sources/headers

Usage Examples

• Evaluate a simple arithmetic expression using p2 flow:

flex p2.l
bison -d p2.y
gcc p2.tab.c lex.yy.c -o p2 -lfl
echo "(2+3)*4" | ./p2

Expected output:

Enter an expression:
Result = 20

• Count tokens in p5_input.c using p5 flow:

flex p5.l
bison -d p5.y
gcc p5.tab.c lex.yy.c -o p5 -lfl
./p5

Expected output (example):

Digits = <n>
Keywords = <k>
Identifiers = <i>
Operators = <o>

Assessment Notes

• The presence of p2.tab.c, p3.tab.c, p5.tab.c and lex.yy.c indicates successful prior runs of bison/flex on corresponding sources.
• When grading or testing:
  • Ensure token types emitted by .l match %token declarations in .y files (e.g., NUM, DIGIT, ID, KEY, OP).
  • For p4.l, provide input/output filenames when prompted; the program reads an input file and writes stripped output.

License

• This repository contains course materials; check with the instructor for distribution policy. No explicit license included.