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Providing an expression that appears to produce side effects may be misleading to programmers who are not aware that these expressions are not evaluated, and in the case of a VLA used in sizeof, have unspecified results. As a result, programmers may make invalid assumptions about program state, leading to errors and possible software vulnerabilities.
This rule is similar to PRE31-C. Do not perform side effects in arguments to unsafe macros.
Noncompliant Code Example (sizeof)
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