Synopsis

Do not use floating-point variables as loop counters

Enabled by default

Yes

Severity/Certainty

Low/Medium

Full description

Because floating-point numbers represent real numbers, it is often mistakenly assumed that they can represent any simple fraction exactly. Floating-point numbers are subject to representational limitations just as integers are, and binary floating-point numbers cannot represent all real numbers exactly, even if they can be represented in a small number of decimal digits. This check is identical to MISRAC2012-Rule-14.1_b.

Coding standards

Code examples

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

void func(void) {
  for (float x = 0.1f; x <= 1.0f; x += 0.1f) {
    /* Loop may iterate 9 or 10 times */
  }
}

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

#include <stddef.h>

void func(void) {
  for (size_t count = 1; count <= 10; ++count) {
    float x = count / 10.0f;
    /* Loop iterates exactly 10 times */
  }
}