Question

Can I check if union is null in c? For example:

union{ char * name, struct Something * something ... }someUnion;

Is there a way to check if no element has been initialized, without doing element vise check?

Thanks.

Answer 1

Yes, under the conditions that all members of the union are of pointer type or a integral type and with initialization you mean a value which is not NULL has been assigned, it is sufficient to check one element for NULL.

union { 
    char * name;
    struct Something * something; } someUnion;

if (someUnion.name != 0) {
    // here you know that someUnion.something is not NULL too.
    // You don't know if it has been initialized as char*
    // or as struct something* though. Presumeably since
    // it is a unionboth interpretations make some sense. 
}