Symbol Table :
- When names are found, they will be entered into a symbol table, which will hold all relevant information about identifiers, function names, objects, classes, interfaces, etc.
- This information will be used later by the semantic analyzer and the code generator.
USAGE OF SYMBOL TABLE BY VARIOUS PHASES OF COMPILER :
.png) |
- Lexical Analysis: Creates new entries in the table about token.
- Syntax Analysis: Adds information regarding attribute type, scope, dimension, line of reference, etc in the table.
- Semantic Analysis: Uses available information in the table to check for semantics i.e. to verify that expressions and assignments are semantically correct(type checking) and update it accordingly.
- Intermediate Code generation: Refers symbol table for knowing how much memory and what type is allocated and table helps in adding temporary variable information.
- Code Optimization: Uses information present in symbol table for machine dependent optimization.
- Target Code generation: Generates code by using address information of identifier present in the table.
SYMBOL TABLE :
Symbol table: A data structure used by a compiler to keep track of semantics of names.
- Determine whether the variable is defined already or not.
- Determine the scope.
- The effective context where a name is valid.
- Where it is stored: storage address.
- Type checking for semantic correctness determination.
Operations:
- Find / Lookup /Search: Access the information associated with given name.
- Insert: add a name into the table.
- Delete: remove a name when its scope is closed