SEMANTIC ANALYSIS – COMPLIER

Syntax analyzer will just create parse tree. Semantic Analyzer will check actual meaning of the statement parsed in parse tree. Semantic analysis can compare information in one part of a parse tree to that in another part (e.g., compare reference to variable agrees with its declaration, or that parameters to a function call match the function definition).

Semantic Analysis is used for the following -

1. Maintaining the Symbol Table for each block.
2. Check Source Program for Semantic Errors.
3. Collect Type Information for Code Generation.
4. Reporting compile-time errors in the code (except syntactic errors, which are caught by syntactic analysis)
5. Generating the object code (e.g., assembler or intermediate code)

Now In the Semantic Analysis Compiler Will Check -

1. Data Type of First Operand
2. Data Type of Second Operand
3. Check Whether + is Binary or Unary.
4. Check for Number of Operands Supplied to Operator Depending on Type of Operator (Unary | Binary | Ternary)

   Analysis Phase : 2nd Phase of Compiler (Syntax Analysis)

   During the first Scanning phase i.e Lexical Analysis Phase of the compiler , symbol table is created by the compiler which contain the list of leximes or tokens.

   Syntax Analysis :

   1. It is Second Phase Of Compiler after Lexical Analyzer
   2. It is also Called as Hierarchical Analysis or Parsing.
   3. It Groups Tokens of source Program into Grammatical Production
   4. In Short Syntax Analysis Generates Parse Tree

   Parse Tree Generation :

   sum = num1 + num2

   Now Consider above C Programming statement. In this statement we Syntax Analyzer will create a parse tree from the tokens.
   

   Syntax Analyzer will check only Syntax not the meaning of Statement

   Explanation : Syntax Analysis

   • We know , Addition operator plus (‘+’) operates on two Operands
   • Syntax analyzer will just check whether plus operator has two operands or not . It does not checks the type of operands.
   • Suppose One of the Operand is String and other is Integer then it does not throw error as it only checks whether there are two operands associated with ‘+’ or not .
   • So this Phase is also called Hierarchical Analysis as it generates Parse Tree Representation of the Tokens generated by Lexical Analyzer