Explore core concepts of error detection and recovery techniques in compilers with this quiz. Assess your knowledge of syntax errors, error-handling strategies, and compiler error messages to strengthen your understanding of programming language compilation.
Which type of error is detected by the syntax analysis phase of a compiler when a programmer accidentally writes 'if x = 5' instead of 'if x == 5'?
Explanation: A syntax error occurs when the structure of the code violates the rules of the programming language, such as using '=' instead of '==' in a conditional statement. Semantic errors involve meaning, logical errors produce incorrect results, and runtime errors occur during program execution. Only a syntax error will be detected at this stage by the syntax analyzer.
What is the main goal of error recovery in compilers during the compilation process?
Explanation: The main objective of error recovery is to allow the compiler to proceed with compilation after encountering an error so that multiple errors can be reported in a single run. Halting compilation immediately would not make efficient use of developers' time. Code optimization and code generation are unrelated to error recovery.
Which error recovery strategy involves the compiler skipping input symbols until it finds a synchronizing token such as a semicolon?
Explanation: Panic mode recovery works by skipping symbols until a well-known synchronizing token is found, which helps the parser resume analysis. Global correction tries to make minimal corrections, phrase level recovery tries simple local changes, and roll-back recovery is not typically a compiler term.
A compiler attempts to minimally change the source code to fix detected errors. What is this technique called?
Explanation: Global correction refers to altering the source input as little as possible to correct the errors, so the compiler can continue processing. Backtracking relates to trying alternative parsing paths, token insertion is just one possible operation, and loop unrolling is an optimization technique unrelated to error recovery.
When a parser corrects a syntax error by deleting, inserting, or replacing a small number of tokens, it is applying which error recovery strategy?
Explanation: Phrase level recovery handles local errors by performing simple corrections like deleting, inserting, or replacing tokens. Lexical substitution and emergency patching are not standard compiler error recovery strategies, while traceback correction is not a common term in error recovery.
Why are synchronizing tokens important in compiler error recovery, particularly in panic mode?
Explanation: Synchronizing tokens, such as semicolons or closing braces, help the parser find a safe point to resume parsing after skipping erroneous input. They do not affect execution speed, memory allocation, or exclusively mark the start of loops. Their function is specifically tied to resuming parsing after errors.
If a compiler encounters an invalid character like '@' in a program, which type of error has occurred?
Explanation: A lexical error arises from unrecognized or illegal characters, as identified in the lexical analysis phase. Semantic errors relate to the meaning of code, linker errors occur during linking, and runtime exceptions are errors during execution, not compilation.
What is the primary reason compilers provide specific error messages, often with line numbers and code snippets?
Explanation: Error messages with details like line numbers allow programmers to efficiently identify and correct mistakes in their code. They are not intended to control execution speed, memory allocation, or enforce code formatting, making the first option the only correct one.
If a variable is used before it is declared, which kind of error is a compiler likely to report?
Explanation: Using a variable before it is declared violates semantic rules, leading to a semantic error. Syntax errors pertain to structure, lexical errors to invalid tokens, and debugger errors are not something a compiler reports. Only semantic errors check for variable declarations and usage.
What is a common drawback of panic mode error recovery in compilers?
Explanation: Panic mode recovery may skip too much code to find a synchronizing token, causing the parser to miss additional errors or context. It does not suppress all error messages, it is simple rather than complex, and it does not cause memory leaks in itself.