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float calcPercentage(float value) {
  return value * 0.1f;
}

void floatRoutine(void) {
  float value = 99.0f;
  floatlong double percentage;

  percentage = calcPercentage(value);
}

...

float calcPercentage(float value) {
  return (float)(value * 0.1f);
}

void floatRoutine(void) {
  float value = 99.0f;
  long floatdouble percentage;

  percentage = calcPercentage(value);
}

...

float calcPercentage(float value) {
  volatile float result;

  result = value * 0.1f;

  return result;
}

void floatRoutine(void) {
  float value = 99.0f;
  long double percentage;

  percentage = calcPercentage(value);
}

Compliant Code Example (Outside the function 1)

Forcing the range and precision inside the calcPercentage() function is a good way to fix the problem once without having to apply fixes in multiple locations (every time calcPercentage() is called).  However, access to the called function may not always be available.  This example shows one way to force the correct range and precision in a situation in which the source of the called function can not be modified.  This is accomplished by casting the return value of the calcPercentage() function to float.

void floatRoutine(void) {
  float value = 99.0f;
  long double percentage;

  percentage = (float)calcPercentage(value);
}

Compliant Code Example (Outside the function 2)

This example shows another way to force the correct range and precision.  In this case a temporary variable is used as the forcing mechanism.

void floatRoutine(void) {
  float value = 99.0f;
  long double percentage;
  float temp;

  percentage = temp = calcPercentage(value);
}

Risk Assessment

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\[[ISO/IEC 9899:1999|AA. C References#ISO/IEC 9899-1999]\]
\[[WG14/N1396|http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1396.htmAA. C References#WG14/N1396]\]