If you want to be more efficient, you can also use a union for this.

typedef union { int i; float f; double d; long l; char c; void *p; ... } var;

Now you might also get some nice float-interpreted-as-int bugs if you forget the type!

You can also kind of pretend that you have C#-style type inference:

var x = { .i = 10 }; var y = { .f = 2.0f };