The sizeof operator yields the size (in bytes) of its operand, which may be an expression or the parenthesized name of a type. If the type of the operand is not a variable length array type, the operand is not evaluated.
Providing an expression that appears to produce side effects may be misleading to programmers who are not aware that these expressions are not evaluated. As a result, programmers may make invalid assumptions about program state, leading to errors and possible software vulnerabilities.
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If expressions that appear to produce side effects are supplied to the sizeof operator, the returned result may be different then than expected. Depending on how this result is used, this could lead to unintended program behavior.
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