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This noncompliant code example can result in prevents divide-by-zero errors in compliance with  INT33-C. Ensure that division and remainder operations do not result in divide-by-zero errors but does not prevent a signed integer overflow error on twos-complement platforms. On the x86-32 architecture, overflow results in a fault, which can be exploited as a  denial-of-service attack.

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Many hardware architectures implement remainder as part of the division operator, which can overflow. Overflow can occur during a remainder operation when the dividend is equal to the minimum (negative) value for the signed integer type and the divisor is equal to −1. This occurs even though the result of such a remainder operation is mathematically 0.  This noncompliant code example prevents divide-by-zero errors in compliance with  INT33-C. Ensure that division and remainder operations do not result in divide-by-zero errors but does not prevent integer overflow.

void func(signed long s_a, signed long s_b) {
  signed long result;
  if (s_b == 0) {
    /* Handle error */
  } else {
    result = s_a % s_b;
  }
  /* ... */
}

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Compliant Solution

This compliant solution also tests the remainder operands to guarantee there is no possibility of an overflow or a divide-by-zero error:

#include <limits.h>
 
void func(signed long s_a, signed long s_b) {
  signed long result;
  if ((s_b == 0 ) || ((s_a == LONG_MIN) && (s_b == -1))) {
    /* Handle error */
  } else {
    result = s_a % s_b;
  }
  
  /* ... */
}

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The C Standard, 6.5.7 paragraph 4 [ISO/IEC 9899:2011], states

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In almost every case, an attempt to shift by a negative number of bits or by more bits than exist in the operand indicates a bug (logic error). These issues are covered by INT34-C. Do not shift a negative number of bits or more bits than exist in the operand.

Noncompliant Code Example

This noncompliant code example can result in an unrepresentable value. 

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Compliant Solution

This compliant solution eliminates the possibility of overflow resulting from a left-shift operation:

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