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In this noncompliant code example, the expression a++ is not evaluated and the side effects in the expression are not executed.

int a = 14;
int b = sizeof(a++);

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In this compliant solution, the variable a is incremented.

int a = 14;
int b = sizeof(a);
a++;

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In the following noncompliant code example, the expression ++n in the initialization expression of a must be evaluated since its value affects the size of the variable length array operand of the sizeof operator. However, since the expression ++n % 1 evaluates to 0, regardless of the value of n, its value does not affect the result of the sizeof operator, and, thus, it is unspecified whether n is incremented or not.

void f(size_t n) {
  size_t a = sizeof(int [++n]);           /* n must be incremented */
  size_t b = sizeof(int [++n % 1 + 1]);   /* n need not be incremented */
  /* ... */
}

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The compliant solution below avoids changing the value of the variable n used in the sizeof expression and instead increments it safely outside of it.

void f(size_t n) {
  size_t a = sizeof(int [n + 1]);
  ++n;

  size_t b = sizeof(int [n % 1 + 1]);
  ++n;
  /* ... */
}

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