Also, sizeof is an operator, not a function, so you can write that as
long_struct_name *foo = malloc(sizeof *foo); long_struct_name *foo = malloc(sizeof *foo);If a type name is used, it always needs to be enclosed in parentheses, whereas variable names and expressions can be specified with or without parentheses.
So
long_struct_name *foo = malloc(sizeof long_struct_name)