MISRA C++:2008 Rule 5-0-5

There shall be no implicit floating-integral conversions

Description

Rule Definition

There shall be no implicit floating-integral conversions.

Rationale

If you convert from a floating point to an integer type, you lose information. Unless you explicitly cast from floating point to an integer type, it is not clear whether the loss of information is intended. Additionally, if the floating-point value cannot be represented in the integer type, the behavior is undefined.

Conversion from an integer to floating-point type can result in an inexact representation of the value. The error from conversion can accumulate over later operations and lead to unexpected results.

Polyspace Implementation

The checker flags implicit conversions between floating-point types (float and double) and integer types (short, int, etc.).

This rule takes precedence over 5-0-4 and 5-0-6 if they apply at the same time.

Troubleshooting

If you expect a rule violation but do not see it, refer to Coding Standard Violations Not Displayed.

Examples

Conversion Between Floating Point and Integer Types

typedef signed int int32_t;
typedef float float32_t;

void func ( )
  {
    float32_t f32;
    int32_t   s32;
    s32 = f32;   //Noncompliant
    f32 = s32;   //Noncompliant
    f32 = static_cast< float32_t > ( s32 ); //Compliant
  }

In this example, the rule is violated when a floating-point type is implicitly converted to an integer type. The violation does not occur if the conversion is explicit.

Check Information

Group: Expressions

Category: Required