53：6：警告：功能类型冲突

Question

#include <stdio.h>
#include <string.h>
struct students{
    char name[50];
    int age;
    int height;
};

int main(int argc, char **argv)
{
    struct students manoj;

    strcpy(manoj.name, "manojkumar");
    manoj.age = 15;

    displaymanoj(&manoj); //print testing \n , name , age 

    return 0;
}

void displaymanoj(struct students *ptr) {
    printf("Testing...............DEBUG\n");
    printf("%s\t%d\n", ptr->name,ptr->age);
    printf("END OF TEST: SUCESS -manoj-");
}

I am learning C and it's working where is use pointer to point to structure variable. I am getting the correct output when I run the program. Just that my Geany IDE giving out some message which I would like to know why.

My Compiler Message as below :

Answer 1

You must declare the functions before calling them.

So your program should look something like

// Includes
// Structure

// Function prototype declaration
// This was what you were missing before
void displaymanoj(struct students *ptr);

int main(int argc, char **argv)
{
    ...
}

void displaymanoj(struct students *ptr) {
    ...
}

Answer 2

Since you have the definition of displaymanoj() isn't seen when you call it from main() , compiler implicitly declares one with return type int which conflicts with the actual one. Note that the implicit declaration has been removed since the C99 standard and is no longer valid.

To fix it:

1) Either move the function displaymanoj() above main()'s definition or
2) Do a forward declaration of displaymanoj() .