Compilers Chapter 4: Semantic Analysis
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Compilers Chapter 4: Semantic Analysis

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Questions and Answers

What are Formalisms known as when the attribute evaluation order can be fixed at compiler construction time?

Strongly Non-Circular Syntax Directed Definitions

How can Synthesized Attributes be evaluated in a bottom-up parser?

By keeping values in the stack

What does an L-Attributed Definition contain?

  • Synthesized attributes only
  • Both synthesized and inherited attributes (correct)
  • Inherited attributes only

    • In L-Attributed Definitions, which attributes do inherited attributes depend on?

    <p>Attributes of symbols to the left in the production and the inherited attribute of A</p> Signup and view all the answers

    What is a translation scheme in the context of a context-free grammar?

    <p>A context-free grammar with attributes associated with grammar symbols and semantic actions in productions</p> Signup and view all the answers

    A ________ translation scheme converts infix expressions to postfix expressions.

    <p>simple</p> Signup and view all the answers

    What is the purpose of semantic analysis in a compiler?

    <p>The purpose of semantic analysis is to ensure that the program has a well-defined meaning, verify properties of the program that aren't caught during earlier phases, and make sure that the user's input program is legal.</p> Signup and view all the answers

    What does semantic analysis involve?

    <p>All of the above</p> Signup and view all the answers

    Semantic analysis can be done during parsing.

    <p>False</p> Signup and view all the answers

    Syntax-Directed Translation is the combination of production and ______ rules.

    <p>semantic</p> Signup and view all the answers

    Match the following attribute types with their definitions:

    <p>Synthesized attributes = Computed from attribute values of its children nodes Inherited attributes = Computed from attributes of the siblings and parent of the node</p> Signup and view all the answers

    Study Notes

    Introduction to Semantic Analysis

    • Semantic analysis is the third phase of a compiler, after lexical analysis and syntactic analysis
    • Its purpose is to analyze the meaning of the source code and ensure it is legal
    • This phase checks for errors such as undeclared variables, type mismatches, and scope violations

    What Does Semantic Analysis Involve?

    • Type checking: ensuring data types are used consistently
    • Label checking: ensuring labels exist and are referenced correctly
    • Flow control checks: ensuring control structures are used correctly
    • Uniqueness checks: ensuring certain names are unique
    • Logical checks: ensuring the program is logically correct

    Syntax-Directed Translation (SDT)

    • SDT is a method for specifying translations of programming language constructs
    • It involves associating attributes with grammar symbols and specifying semantic rules for computing attribute values
    • There are two types of attributes: synthesized (computed from child nodes) and inherited (computed from parent or sibling nodes)

    Syntax-Directed Definitions (SDD)

    • SDD is a representation formalism for semantic analysis
    • It involves specifying grammar productions with associated semantic rules for computing attribute values
    • SDD can be implemented using dependency graphs or translation schemes

    S-Attributed Definitions

    • S-Attributed Definitions are a type of SDD that uses only synthesized attributes
    • Evaluation order is determined by a bottom-up traversal of the parse tree
    • Example: arithmetic expressions with synthesized attributes for values

    L-Attributed Definitions

    • L-Attributed Definitions are a type of SDD that uses both synthesized and inherited attributes
    • Evaluation order is determined by a combination of bottom-up and top-down traversals of the parse tree
    • Example: type checking with inherited attributes for type information

    Translation Schemes

    • Translation schemes are a way to specify the order of semantic actions and attribute evaluations
    • They involve inserting semantic actions into the right-hand side of productions
    • Example: a translation scheme for converting infix expressions to postfix notation

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    Description

    This quiz covers the concepts of semantic analysis, syntax-directed translation, and attribute grammars in compiler design.

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