compile error unknown type

Question

When I try to have a struct as an element in another struct I get the following error

if I use simple data types I don't get the error

Einar Thorsrud · Answer

Hi, 
 This is because you have not declared a_struct as a type. 
 So you either need to modify it so that it is declared with typedef like this: 
 typedef struct {
 uint32_t variable1;
 uint32_t variable2;
} a_struct; 
 or , use it like this (with struct ): 
 typedef struct {
 struct a_struct var1;
 struct a_struct var2;
} b_struct;