C5919: Conversion of floating to unsigned integral

[WARNING]

In ANSI-C the result of a conversion operation of a (signed) floating type to a unsigned integral type is undefined. One implementation may return 0, another the maximum value of the unsigned integral type or even something else. Because such behavior may cause porting problems to other compilers, a warning message is issued for this.

    float f = -2.0;

  

    unsigned long uL = f; // message C5919 here

  

To avoid the undefined behavior, first assign/cast the floating type to a signed integral type and then to a unsigned integral type.

• ISO/IEC 9899:1990 (E), page 35, chapter 6.2.1.3 Floating and integral: "When a value of floating type is converted to integral type, the fractional part is discarded. The value of the integral part cannot be represented by the integral type, the behavior is undefined."