Compilers Chapter 4: Semantic Analysis

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11 Questions

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?

Both synthesized and inherited attributes

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

Attributes of symbols to the left in the production and the inherited attribute of A

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

A context-free grammar with attributes associated with grammar symbols and semantic actions in productions

A ________ translation scheme converts infix expressions to postfix expressions.

simple

What is the purpose of semantic analysis in a compiler?

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.

What does semantic analysis involve?

All of the above

Semantic analysis can be done during parsing.

False

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

semantic

Match the following attribute types with their definitions:

Synthesized attributes = Computed from attribute values of its children nodes Inherited attributes = Computed from attributes of the siblings and parent of the node

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

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

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