Question

I declare a new struct with the name of “Struct”
I have a generic function that takes in an argument “void *data”.

void Foo(void *data)

I pass an instance of “Struct” into the generic function.

Struct s;
Foo(&s);

I want to access one of the properties of the struct in the function.

void Foo(void *data) {
    char *word = (char*) data.word;
}

It’s not allowed because it doesn’t recognize data as a valid struct.

I even try to declare the data as the struct type first, and I get an error.

void Foo(void *data) {
    Struct s = (Struct) data;
    char *word = s.word;
}

I get “conversion to non-scalar type requested”.

Answer 1

First of all, you should turn on your compiler’s warning flags (all of them). Then you should pass a pointer to your Struct and use something other than struct as a variable name:

Struct s;
Foo(&s);

Then, in Foo:

void Foo(void *data) {
    Struct *s    = data;
    char   *word = s->word;
}

You can’t convert non-pointer types to and from void* like you’re trying to, converting pointer types to and from void* is, on the other hand, valid.