Page History

...

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

...

In the assignments above, it is possible that the variable "d1" exceeds the maximum value that can be stored by a float or that the variable "ld" exceeds the maximum value that can be stored in either a float or a double.  One cannot make any assumptions about the value stored if the value is too large to be represented.

Compliant Code Example

This compliant code properly checks to see whether the values to be stored are too large to be represented.

#include <float.h>

...

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

...

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

...