Can C Structures Be Initialized Using Designated Initializers for Pointer Members?

C Structure Initialization

It has been questioned whether it is possible to initialize structures in C using the following syntax:

struct address {
    int street_no;
    char *street_name;
    char *city;
    char *prov;
    char *postal_code;
};

address temp_address = { .city = "Hamilton", .prov = "Ontario" };

While some sources suggest that this style is only supported in C, this is not entirely accurate.

Technical Limitations

Although C supports structure initialization using designated initializers, there is a technical limitation: designated initialization is not supported for members that are pointers or references. Since street_name, city, prov, and postal_code are all pointers in the provided example, the designated initialization syntax cannot be used to initialize these members.

Best Practices and Readability

While the designated initialization syntax can provide clear readability, it is generally considered best practice to initialize structures using a combination of default constructors and explicit member initialization. This allows you to specify which members to initialize explicitly and which to leave uninitialized.

For example, you can initialize the temp_addres structure as follows:

address temp_addres = {
  0,  // street_no
  nullptr,  // street_name
  "Hamilton",  // city
  "Ontario",  // prov
  nullptr,  // postal_code
};

This approach provides clear readability by using comments to identify each member and its value. Additionally, it ensures that any pointers not explicitly initialized are set to nullptr for safety.

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