Incompatible pointer type when making structure of function pointers

Question

I'm trying to make a array of structures which contain a string and a function pointer, however when I compile I get a warning that I've initialized from an incompatible pointer type.

I have no idea why (sorry if I sound ignorant, I'm fairly new to C programming).

 typedef struct
{
    char Player1[2], Player[2], **gameGrid;
    int height,width;
    int moveNum, player1Num, player2Num;
    bool player1Win, player2Win;
}Game;

typedef int (*pointer_func)(Game *);

typedef struct
{
   char *funcName;
   pointer_func *f;
}userFunc;

int save(Game *struc);
int load(Game *struc);
int move(Game *struc);
int quit(Game *struc);
void free_grid(Game *struc);


int main(){
//initialised variables 

userFunc Name_arr[] = {
    {"save",save},
    {"load",load},
    {"quit",quit},
    {"move",move}
};

The four functions being referenced are as follows:

int save(Game *struc)
{
char *str, *inputString, *writeString;
FILE *fp;
int nextPlayer;
int maxRead = 20;
bool DIRresponse;

while(true)
{
    printf("Please provide a file name (20 characters max): ");
    inputString = input_String(inputString, maxRead, stdin);

    if((DIRresponse = check_Directory(inputString)) == true){
        printf("That name already exists, choose another\n");
        continue;
    }
    else
        break;  
}

if(struc->moveNum % 2 == 0)
    nextPlayer = struc->player1Num;
else
    nextPlayer = struc->player2Num;

sprintf(str,"%s.txt",inputString);
fp = fopen(str,"w");

sprintf(writeString, "%d %d %d %d %d",  nextPlayer, struc->height,
            struc->width, struc->moveNum, struc->moveNum);
fprintf(fp,writeString);

fclose(fp);

return 0;
}

int move(Game *struc)
{
 return 1;
}

int load(Game *struc)
{
 return 1;
}

int quit(Game *struc)
{
 free_grid(struc);
 exit(EXIT_SUCCESS);
}

Please post the exact text of the compiler warning, and if needed, indicate where the line is in your code. — Ken Y-N
– Ken Y-N, Commented Jan 26, 2018 at 7:23
try to explicity cast and set values : userFunc Name_arr[] = { (userFunc){ .funcName = "save", .f = save} /* other array items */ }; — ArhiChief
– ArhiChief, Commented Jan 26, 2018 at 7:25
pointer_func is already a pointer, you have pointer to pointer to function initialized with pointer to functions. — Bob__
– Bob__, Commented Jan 26, 2018 at 7:26
BTW, you don't allocate any space for str or write_string, and the sprintf can be merged with the fprintf. — Ken Y-N
– Ken Y-N, Commented Jan 26, 2018 at 7:28

Gerhardh · Accepted Answer · 2018-01-26 07:27:29Z

4

You have a mismatch in levels of pointers:

typedef int (*pointer_func)(Game *); << Pointer type

typedef struct
{
  char *funcName;
  pointer_func *f;              << Pointer to a pointer type.... OOPS
}userFunc;

Make *f -> f and it should work.

answered Jan 26, 2018 at 7:27

Gerhardh

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2 Comments

Mr_incompetent Over a year ago

Ahhh, I always feel so stupid after being shown what I've overlooked, regardless thank you for the swift and elegant response.

Gerhardh Over a year ago

Good. Then you will remember it and don't do it again. ;)

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