Synopsis

Do not use object representations to compare floating-point values.

Enabled by default

Yes

Severity/Certainty

Low/Low

Full description

Do not compare floating-point object representations directly, such as by calling memcmp() or its moral equivalents. Instead, the equality operators (== and !=) should be used to determine if two floating-point values are equivalent.

Coding standards

Code examples

The following code example fails the check and will give a warning:

#include <stdbool.h>
#include <string.h>

struct S {
  int i;
  float f;
};

bool are_equal(const struct S *s1, const struct S *s2) {
  if (!s1 && !s2)
    return true;
  else if (!s1 || !s2)
    return false;
  return 0 == memcmp(s1, s2, sizeof(struct S));
}

The following code example passes the check and will not give a warning about this issue:

#include <stdbool.h>
#include <string.h>

struct S {
  int i;
  float f;
};

bool are_equal(const struct S *s1, const struct S *s2) {
  if (!s1 && !s2)
    return true;
  else if (!s1 || !s2)
    return false;
  return s1->i == s2->i &&
         s1->f == s2->f;
}