Assign multiple values to array in C

Although in your case, just plain initialization will do, there's a trick to wrap the array into a struct (which can be initialized after declaration).

For example:

struct foo {
  GLfloat arr[10];
};
...
struct foo foo;
foo = (struct foo) { .arr = {1.0, ... } };

If you really to assign values (as opposed to initialize), you can do it like this:

 GLfloat coordinates[8]; 
 static const GLfloat coordinates_defaults[8] = {1.0f, 0.0f, 1.0f ....};
 ... 
 memcpy(coordinates, coordinates_defaults, sizeof(coordinates_defaults));

 return coordinates;