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Non-Compliant Code Example

This non-compliant code example illustrates possible undefined behavior associated with demoting floating point represented numbers.

long double ld;
double d1;
double d2;
float f1;
float f2;

/* initializations */

f1 = (float)d1;
f2 = (float)ld;
d2 = (double)ld;

In the assignments above, As a result of these conversions it is possible that the variable d1 is outside the range of values that can be represented by a float or that the variable ld is outside the range of values that can be represented as either a float or a double.

Compliant Solution

This compliant code solution properly checks to see whether the values to be stored can be represented properly in the new type.

#include <float.h>

long double ld;
double d1;
double d2;
float f1;
float f2;

/* initializations */

if (d1 > FLT_MAX || d1 < -FLT_MAX) {
  	/* Handle error condition */
} else {
 	f1 = (float)d1;
}
if (ld > FLT_MAX || ld < -FLT_MAX) {
	/* Handle error condition */
} else {
	f2 = (float)ld;
}
if (ld > DBL_MAX || ld < -DBL_MAX) {
	/* Handle error condition */
} else {
	d2 = (double)ld;
}

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