Compiler Design - OC

All source code can be found HERE

SYNOPSIS

oc [-ly] [-@ flag ...] [-D string] program.oc

OPTIONS

• -@ flags: Call set_debugflags, and use DEBUGF and DEBUGSTMT for debugging.
• -D string: Pass this option and its argument to cpp. Use -D__OCLIB_OH__ to suppress inclusion of the code from oclib.oh when testing a program.
• -l: Debug yylex() with yy_flex_debug = 1.
• -y: Debug yyparse() with yydebug = 1.

OUTPUT FILES

The 5 Stages of Compilation

1. I. Preprocessor and token generation
2. II. Lexical Analyzer (using flex)
3. III. LALR(1) Parser (using bison)
4. IV. Symbols and Type Checking
5. V. Intermediate Language Emission

I. Preprocessor and String Set Generation

The first part of the compiler consisted of writing a main program for the language oc. Included in it was a string set ADT used to create unique string sets based on the output from the C preprocessor.

The purpose of the string set is to keep track of strings uniquely. For example, if “abc” is entered multiple times, it appears only once in the table. This allows the compiler to compare pointers instead of using strcmp(3).

II. Lexical Analyzer

The second part augmented the string table into a scanner written in flex. Tokens are identified based on regex in the scanner.l file.

• Special symbols: [] ( ) [ ] { } ; , . = == != < <= > >= + - * / % !
• Reserved words: void bool char int string struct if else while return false true null ord chr new
• Identifiers: Sequences of letters, digits, and underscores (cannot start with a digit).
• Constants: Supports Integer (decimal only), Char, and String constants.

III. LALR Parser

This stage involved writing an LALR parser using bison.

• AST Construction: Operators become parents of their operands (children). Children can be leaf nodes (identifiers/constants) or other expression nodes.