KTU S7 Compiler Design - Lab

Mar Baselios College Of Engineering And Technology (2024-25)

This README provides instructions on how to compile and run C programs, Lex files, and integrate Lex with Yacc for the KTU S7 Compiler Design Lab.

Compiling and Running C Programs

Standard Method

1. Compile the C program:

   gcc filename.c -o program_name

2. Run the compiled program:

   ./program_name

For NixOS Users

1. Enter a nix-shell with gcc:

   nix-shell -p gcc

2. Compile and run as normal:

   gcc filename.c -o program_name
   ./program_name

Running Lex Files

Method 1: Using Flex and gcc with -lfl

flex filename.l
gcc lex.yy.c -o lexer -lfl
./lexer

Method 2: Using Lex and gcc with -ll

lex filename.l
gcc lex.yy.c -o lexer -ll
./lexer

Method 3: Using Flex and gcc without specifying the library

flex filename.l
gcc lex.yy.c
./a.out

Method 4: Using a build script

1. Create a file named build.sh with the following content:

   #!/bin/bash
   flex "$1"
   gcc lex.yy.c -o lexer -lfl
   ./lexer

2. Make the script executable:

   chmod +x build.sh

3. Run the script:

   ./build.sh filename.l

For NixOS Users

1. Add flex and bison to your configuration file:

   environment.systemPackages = with pkgs; [
     flex
     bison
   ];

2. Rebuild your system:

   sudo nixos-rebuild switch

3. Use nix-shell to run the files:

   nix-shell -p flex
   flex lex.l
   gcc lex.yy.c -o lexer -lfl
   ./lexer

Integrating Lex and Yacc

1. Write your Lex (.l) and Yacc (.y) files.
2. Generate C files:

   flex lexer.l
   bison -d parser.y

3. Compile the generated C files:

   gcc -c lex.yy.c parser.tab.c

4. Link the object files:

   gcc lex.yy.o parser.tab.o -o parser -lfl

5. Run the parser:

   ./parser

For a detailed guide on Lex and Yacc integration, refer to the Lex-Yacc Integration Guide.

Troubleshooting

• For "undefined reference to yywrap" error:
  1. Add %option noyywrap at the top of your Lex file, or
  2. Define yywrap() in your Lex file:

     int yywrap() { return 1; }

• For "cannot find -lfl" or "cannot find -ll" errors on Ubuntu or Debian:

  sudo apt-get install libfl-dev

Note

Ensure you have Flex (or Lex), Bison (or Yacc), and gcc installed on your system before compiling Lex files, Yacc files, or C programs.

For more information:

• Official Flex documentation
• GNU Bison Manual