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Passing array of type char** as an argument of type void** gives unexpectable warning

I have a warning when passing a pointer array (char**) as an argument of type void** in a function.

Below is my code. I use gcc compiler, it gives me this warning:

"warning: passing argument 1 of 'print' from incompatible pointer type [enabled by default]".

It points to this line print(lineptr, 2);

And another warning says:

warning: format '%s' expects argument of type 'char *', but argument 2 has type 'void *'.

And it points to this line printf("%s\n", *v++);

I tried replacing all void** with char** and it works well.

The reason that I want to use void** is that I'm writing a quicksort function that can receive both character or integer arrays.

#include <stdio.h>
char *lineptr[100] = {"mister", "x"};
void print(void **, int n);
int main()
{
    print(lineptr, 2);
    return 0;
}
void print(void **v, int n)
{
    while( n-- > 0 )
        printf("%s\n", *v++);
}

The question is: does this warnings affect anything?

Now, I'm having no problems running the code and getting a desired output, but I asks if this method is guaranteed to work well every time.

Solution

  • You could cast the char array to void:

    print((void **)lineptr, 2);

    Generally it's best to pay attention to warnings and fix the issues to avoid undefined behavior.