struct redefinition

This is a discussion on struct redefinition within the C Programming forums, part of the General Programming Boards category; the following code is the header file for the game/2d engine I'm making. When I build my program I get ...

  1. #1
    Registered User Draco's Avatar
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    struct redefinition

    the following code is the header file for the game/2d engine I'm making. When I build my program I get the error message that in the first function definition for collision() that the person struct is being redefined. I looked to make sure my function definition was right, and even tried looking in the K&R book. Maybe I'm getting too tired, but I couldnt find anything that would help the error message make sense of what I did wrong.

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <allegro.h>
    
    #define ALLEGRO_USE_CONSOLE
    #define BULLET_VEL 3
    #define DEAD 0
    #define DYING -1
    #define ALIVE 1
    #define LEFT 0
    #define RIGHT 1
    #define PBULLETS 8
    #define EBULLETS 32
    
    struct person{
                    int x,y;
                    int width, height;
                    float x_vel, y_vel;
                    int alive;
                    int direction;
                    BITMAP *sprite;				
    };
    
    struct bullet{
                    int x,y;
                    int width, height;
                    float vel;
                    bool exists;
                    int num_bullets;		
    };
    
    
    
    bool collision(struct* person,struct* person);
    bool fire_bullet(struct* person,struct* bullet);
    void frames_per_sec(void);
    bool hit(struct* person);
    void update_bullets(void);
    Last edited by Draco; 07-26-2004 at 01:38 AM.

  2. #2
    Registered User The Dog's Avatar
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    Maybe it's because you're using the same argument name in the function declaration.

    change this:
    bool collision(struct* person,struct* person);

    to this:
    bool collision(struct* personA,struct* personB);

    or something of the sort.

  3. #3
    and the hat of wrongness Salem's Avatar
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    > bool collision(struct* person,struct* person);
    Don't you mean

    bool collision(struct person * me, struct person *you);
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  4. #4
    Registered User Draco's Avatar
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    Salem, that's how I had it originally, but I got those error messages, and moving them to how I had posted took some away.

  5. #5
    Obsessed with C chrismiceli's Avatar
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    Could you post the exact error message. If you take Salem's advice, the prototypes should be right.
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  6. #6
    Registered User Draco's Avatar
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    Code:
    c:\program files\microsoft visual studio\myprojects\action game 3\actiongame3.h(34) : error C2371: 'person' : redefinition; different basic types
            c:\program files\microsoft visual studio\myprojects\action game 3\actiongame3.h(34) : see declaration of 'person'
    This error message is there no matter if the prototype is correct or not. I also noticed that there has never been a similar error for the bullet structure in my fire_bullet() function.

  7. #7
    Obsessed with C chrismiceli's Avatar
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    That usually means you are trying to define person twice, which is invalid. Are you including a header file twice inadvertantly? Make sure there is no way that person can be defined twice.
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  8. #8
    Helper
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    Quote Originally Posted by Draco
    Code:
    struct person{
    <...>
    };
    
    struct bullet{
    <...>
    };
    
    <...>
    bool collision(struct* person,struct* person);
    bool fire_bullet(struct* person,struct* bullet);
    bool hit(struct* person);
    <...>
    The function prototypes are buggy. 'struct' is not a struct. You need a tag:
    'struct person'
    'struct bullet'
    Code:
    bool collision(struct person* ,struct person*);
    bool fire_bullet(struct person*,struct bullet*);
    bool hit(struct person*);
    Last edited by Emmanuel Delaha; 07-26-2004 at 12:30 PM. Reason: cut
    Emmanuel Delahaye

    "C is a sharp tool"

  9. #9
    Registered User Draco's Avatar
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    well I could tell that my prototypes were bad....but thanks, when I changed it to that it fixed it.

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