Thread: The function declared with const issues a warning

My code:

Code:

#include <stdio.h>

const void write()
{
	FILE *f;
	char Text[]="Test\n";
    if ((f = fopen("text.txt","a")) == NULL)
        printf("Error\n");
    else
        fwrite(&Text, 5, 1, f);
    fclose(f);
}

int main()
{
	write();
}

When compiling, warnings are displayed:

test.c:3:12: warning: function definition has qualified void return type
const void write()
^
test.c: In function ‘main’:
test.c:16:2: warning: function with qualified void return type called
write();
^

I have read this in the K&R manual on page 84. Is the textbook wrong?

There is a Standard Library function called "write". You are redefining it! Please rename yours.

Even renaming it to my_write(), it should only write to an open file not open it as well.

A function should do one thing only, and do it well. Open the file in main() or in a separate function.

Const here makes no sense at all. Const makes sense if you are actually returning data. Void means the function returns NO data! Please drop the const.

In addition, const on return data really only makes sense if you are returning a pointer to const data.

Originally Posted by rstanley

In addition, const on return data really only makes sense if you are returning a pointer to const data.

Code:

#include <stdio.h>

static void print()
{
	printf("Ok!\n");
}

int main(int atgc, char *argv[])
{
	FILE *f;
	char Text[]="Test\n";
    if ((f = fopen("text.txt","a")) == NULL)
       printf("Error\n");
   else
        fwrite(Text, 9, 1, f);
    fclose(f);
    print();
}

t turns out to confuse const with static! Now everything works and does not give out any warnings. Problem solved