MISRA.CVALUE.IMPL.CAST.CPP

The value of an expression should not be implicitly converted to a different type.

MISRA-C++ Rule 5-0-3 (required): A cvalue expression shall not be implicitly converted to a different underlying type.

Rationale

In order to ensure all operations in an expression are performed in the same underlying type, an expression defined as a cvalue shall not undergo further implicit conversions.

Example

void f ( )
{
   int32_t s32;
   int8_t s8;

   s32 = s8 + s8;                                // Example 1 —

                                                 // Non-compliant
   s32 = static_cast < int32_t > ( s8 ) + s8;    // Example 2 - Compliant
   s32 = s32 + s8;                               // Example 3 - Compliant
}

In Example 1, the addition operation is performed with an underlying type of 'int8_t' and the result is converted to an underlying type of 'int32_t'.

In Examples 2 and 3, the addition is performed with an underlying type of 'int32_t' and therefore no underlying type conversion is required.