Question

There’s a header file, esUtil.h, with a definition for a structure called ESContext, and one of its members is userData. userData is a pointer to void.

The body of a program using it is this, briefly:

#include "esUtil.h"

typedef struct {
 GLuint programObject;
} UserData;

int DoSomething(ESContext *esContext) {
 UserData *userData = esContext->userData;

 ...
}

int main(int argc, char *argv[]) {
 ESContext esContext;
 UserData userData;

 esStart(&esContext);
 esContext.userData = &userData;

 ...
 if(!DoSomething(&esContext))
  return 0;

 ...
}

I’m confused by what “*userData” is in the statement: UserData *userData = esContext->userData;

And if it is a pointer, how it came into being without being declared. Thanks for any explanations.

Answer 1

Yes, it is a pointer. The line

UserData *userData = esContext->userData;

declares a variable called userData with type UserData * (a pointer to UserData) and initializes it with the value esContext->userData.