Why are C enum classes safer than plain enums?

Enum Classes: Enhanced Type Safety in C

Question:

Why are enum classes considered safer to use than plain enums in C ?

Answer:

C provides two types of enums: enum classes and plain enums. While plain enums offer similar functionality, enum classes have an important advantage: improved type safety.

Type Safety Differences:

• Plain enums: Their enumerators are in the same scope as the enum itself. Their values implicitly convert to integers and other types.
• Enum classes: Their enumerators are local to the enum. Their values do not implicitly convert to other types.

Consequences of Implicit Conversion:

With plain enums, the implicit conversion of their values can lead to unexpected behavior and potential bugs. For example, a plain enum called Color and another called Card may have a shared enumerator value, such as red. If code assigns a plain enum value to an int variable, or compares values from different enums, unintentional errors can occur.

Type Safety in Enum Classes:

Enum classes prevent these issues by isolating their enumerator values. As a result, their values cannot be directly compared or converted to other types. This restriction eliminates a common source of errors and promotes safer code.

Example:

enum class Animal { dog, deer, cat, bird, human };
enum class Mammal { kangaroo, deer, human };

// Error: Different enum classes cannot be compared
if (Animal::deer == Mammal::deer)    // Error

// Error: Enum class values cannot be implicitly converted to int
int num = Animal::deer;   // Error

Conclusion:

By isolating enumerator values and preventing implicit conversion, enum classes enhance type safety in C code. This reduces the risk of unintended data conversions and potential bugs, making enum classes a more reliable choice for enumerations.

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