In the source code below, could somebody explain the rational (why is it good programming practice to typedef the struct _lwm2m_object_t with the new name lwm2m_object_t? All it does is drop the underscore? Why is an underscore used in the first instance?
typedef struct _lwm2m_object_t lwm2m_object_t;
typedef uint8_t (*lwm2m_read_callback_t) (lwm2m_uri_t * uriP, char ** bufferP, int * lengthP, lwm2m_object_t * objectP);
typedef uint8_t (*lwm2m_write_callback_t) (lwm2m_uri_t * uriP, char * buffer, int length, lwm2m_object_t * objectP);
typedef uint8_t (*lwm2m_execute_callback_t) (lwm2m_uri_t * uriP, char * buffer, int length, lwm2m_object_t * objectP);
typedef uint8_t (*lwm2m_create_callback_t) (lwm2m_uri_t * uriP, char * buffer, int length, lwm2m_object_t * objectP);
typedef uint8_t (*lwm2m_delete_callback_t) (uint16_t id, lwm2m_object_t * objectP);
typedef void (*lwm2m_close_callback_t) (lwm2m_object_t * objectP);
struct _lwm2m_object_t
{
uint16_t objID;
lwm2m_list_t * instanceList;
lwm2m_read_callback_t readFunc;
lwm2m_write_callback_t writeFunc;
lwm2m_execute_callback_t executeFunc;
lwm2m_create_callback_t createFunc;
lwm2m_delete_callback_t deleteFunc;
lwm2m_close_callback_t closeFunc;
void * userData;
};
Actually if you use
typedef struct lwm2m_object_t lwm2m_object_t;
struct lwm2m_object_t {
//
}
It will still be allowed by C. This is because the structure names and the typedef identifiers have different namespaces. Please see Why doesn't ANSI C have namespaces? for information about namespaces in C.
However, many professional users avoid this and use different names for structures and typedefs. MISRA1 also disallows this.
Rule 5.6 (advisory): No identifier in one name space should have the same spelling as an identifier in another name space, with the exception of structure member and union member names. [MISRA C 2004]
The use of underscore is just a convention that some people follow. You can follow other conventions, e.g.
typedef struct sTag_lwm2m_object_t lwm2m_object_t;
struct sTag_lwm2m_object_t {
//
}