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Struct Advance declaration ERROR C52

Arnaud Sourdrille 

/** Advance Declaration **/
struct    enreg;
typedef   enreg Ts_Enreg;

/** Prototypes **/
extern unsigned char  MyFunc_1( Ts_Enreg * objects );
extern unsigned char  MyFunc_2( Ts_Enreg   objects[]);

MyFunc_1 and MyFunc_2 prototypes are equivalent, but C251 raises an error C52: Use of undefined type 'enreg'.

Why ?

C251 version : v5.58.17.0

PS : There is a complete description of the structure 'enreg' in the program source.

Arnaud

  • 0 

    typedef   enreg Ts_Enreg;

    That doesn't do what you believe it does. It relies on there being a typedefed or #defined type 'enreg' present, but there isn't. If your textbook claims this is supposed to work, you need a different one, because the one you have is not actually about the C programming language.

    MyFunc_1 and MyFunc_2 prototypes are equivalent

    No, they're not. It's one thing to declare a function that takes an unknown type, but quite a different one if it takes a pointer to that unknown type.