mca401-compiler-design

Coursework for mca401-compiler-design

We use GNU's flex bison for all the codes.

package requirements

• gnu's lex yacc sudo apt-get install bison flex
• make utility sudo apt-get install build-essential

Question Answers

How to compile lex yacc programs

Perform the following steps, in order to compile a demo program-

• yacc -d demo.yacc Process the yacc grammar file using the -d flag (which tells the yacc command to create a file that defines the tokens used in addition to the C language source code)
• Use ls to verify that the following files were created -
  • y.tab.c The C language source file that the yacc command created for the parser.
  • y.tab.h A header file containing define statements for the tokens used by the parser.
• lex demo.lex Process the lex specification file
• Use ls to verify that the following file was created -
  • lex.yy.c The C language source file that the lex command created for the lexical analyzer.
• cc y.tab.c lex.yy.c -o demo Compile and link the two C language source files.
• Use ls to verify that the following files were created -
  • demo The executable program file

Guide to writing a yacc program

• Identify the Terminal and Non-Terminal Symbols from the BNF and Lex.
• Try coding all the grammar rules in yacc with empty actions.
  • Compile,link it to Lex and check for conflicts.
  • This is an easy way of validating the BNF for reduce/reduce and shift/reduce conflicts.
• Search for any reduce/reduce conflict. Resolve it in Lex. Resolve any shift/reduce conflicts.
• Write rules for all possible syntax errors.Details on error handling are given later.
• Code the yyerror function in subroutine section.
• Design the Data Structure which can be easily integrated with the grammar rules for syntax directed translation.
• From the Data Structures and Lex needs ,formulate the correct Stack.The stack must have pointers for all the data structures.
• Do the appropiate type binding to all tokens and yacc variables (non-terminals).
• Write all the data structures in a seperate file and inlude it in yacc.
• Code all the actions.
• Restrict the actions in case of error, i.e no data structure should be built but parsing should continue to get more errors.

Reference links

• Lex Yacc Introduction

  • http://epaperpress.com/lexandyacc/intro.html
  • http://dinosaur.compilertools.net/lex/
  • http://dinosaur.compilertools.net/yacc/

• Lex yacc primer

  • http://tldp.org/HOWTO/Lex-YACC-HOWTO-7.html