MISRA.FLOAT.BIT.REPR

Use of bit manipulations of floating-point values which rely on storage layout.

MISRA-C Rule 12.12 (required): The underlying bit representations of floating-point values shall not be used.

[Unspecified 6; Implementation 20]

The storage layout used for floating-point values may vary from one compiler to another, and therefore no floating-point manipulations shall be made which rely directly on the way the values are stored. The in-built operators and functions, which hide the storage details from the programmer, should be used.

MISRA-C++ Rule 3-9-3 (required): The underlying bit representations of floating-point values shall not be used.

[Implementation 3.9.1(8)]

Rationale

The storage layout used for floating-point values may vary from one compiler to another, and therefore no floating-point manipulations shall be made which rely directly on the way the values are stored. The in-built operators and functions, which hide the storage details from the developer, should be used.

Example

float32_t My_fabs ( float32_t f )
{
   uint8_t * pB = reinterpret_cast< uint8_t * >( &f );

   *( pB + 3 ) &= 0x7f;   // Non-compliant — generate the absolute value
                          // of an IEEE-754 float value.
   return ( f );
}