IPA FE Subject A sample Question 9

Write the processing for when a memory allocation fails — coding standards set rules that make programs reliable and easy to read, and handling a failed call is one of them.

A memory allocation function (such as malloc in C) returns an error value, typically a null pointer, when it cannot reserve the area. A program that uses the result without checking it crashes or corrupts memory at run time, so coding standards require the result to be checked and the failure to be handled.

Answer (d)

Why not others:

• •(a) — reusing one local variable for different purposes because the type matches makes the code hard to read and invites mistakes; standards ask for one variable per purpose, with a meaningful name
• •(b) — floating-point loop counters accumulate rounding errors, so the loop may run once too often or too rarely, and they are not faster; standards require integer control variables
• •(c) — recursion for a repeated calculation costs a call and stack space each time and can overflow the stack; a loop is usually preferred, and recursion is never a rule a standard imposes for this

Key rule: Coding standards aim at readability, maintainability and reliability: one purpose per variable, integer loop counters, and a check on every call that can fail.

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