`typedef` vs. `using` in C : What's the Difference and When Should I Use Which?

Understanding the Distinction Between 'typedef' and 'using' in C

In C , 'typedef' and 'using' serve as mechanisms to define type aliases. While 'typedef' has been traditionally used for this purpose, 'using' was introduced in C 11 to provide an alternative syntax.

Equivalence and Differences

As per the C standard, 'using' is semantically equivalent to 'typedef'. In both cases, an alias is created, allowing the programmer to use the new name to refer to the original type. This aliasing is considered "weak" in the sense that it does not define a new type but rather associates a new name with the existing type.

Template Type Aliases

While 'typedef' does not support template type aliases, 'using' can be utilized to define them. This feature emerged as a means to express type aliases in the context of templates:

template<class T> using MyType = AnotherType<T, MyAllocatorType>;

Conclusion

In essence, 'typedef' and 'using' offer interchangeable mechanisms for defining type aliases. However, 'using' provides the added advantage of supporting template type aliases, a feature that expands the flexibility of type aliasing in C code.

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