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GATE CSE 2025 Session 2 Q21: Backpatching for Boolean and flow-of-control code

Question

Consider the following statements about the use of backpatching in a compiler for intermediate code generation:

(I) Backpatching can be used to generate code for Boolean expression in one pass.

(II) Backpatching can be used to generate code for flow-of-control statements in one pass.

Which ONE of the following options is CORRECT?

Try it: multiple choice: exactly one correct option

Select one option
Wrong answer costs 1/3 mark in GATE.
Show answer and explanation

Answer: C (official GATE 2025 final answer key)

Concept used: Backpatching keeps lists of jumps with unfilled targets and fills them once the labels are known.

First step: Recall the standard uses of truelist/falselist (Boolean expressions) and nextlist (if, while statements).

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Source: official GATE 2025 Session 2 CS question paper and final answer key, organised by IIT Roorkee. Question paper · Answer key

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