Thread: why this warning's? but compiles

warning:

format %s expects type char * , but argument 2 has type char **

from this piece of code:

Code:

#include <stdio.h>
main()
{
	char *colors[3][10] = {'\0'};
	printf("\nEnter 3 colors seperated by spaces: ");
	scanf("%s %s %s", colors[0], colors[1], colors[2]);
	printf("\nYour entered: ");
	printf("%s %s %s\n", colors[0], colors[1], colors[2]);
}

AND

warning: format '%s' expects type 'char *', but argument 2 has type 'char (*)[3]'

from this piece of code:

Code:

#include <stdio.h>

int main( void ) {
	char tab[2][3] = {'1', '2', '\0', '3', '4', '\0'};
	printf("%s\n", tab);
	
	return 0;
}

Thanks!

Basically, it is expected that you will provide a pointer to char to match with a %s format specifier. However, tab is an array of 2 arrays of 3 char. When you pass it as an argument, it is converted to a pointer to an array of 3 char. Clearly, a pointer an array of 3 char is not a pointer to a char.

The first one has a similiar problem. You probably want colors to be an array of 3 arrays of 10 chars, i.e.,

Code:

char colors[3][10] = {""};

Code:

#include <stdio.h>
main()
{
char *colors[3][10] = {'\0'};
printf("\nEnter 3 colors seperated by spaces: ");
scanf("%s %s %s", colors[0], colors[1], colors[2]);
printf("\nYour entered: ");
printf("%s %s %s\n", colors[0], colors[1], colors[2]);
}

Dont you mean char colors[3][10]?

Code:

char *colors[3][10] = {'\0'};

You declared an array of arrays of pointers to char. Doubt you want that. Because you cant store anything in a pointer unless you have mallocated space for him.
char a[25] = "limited to 25 chars"; //a is alocated
char *ptr; //space not allocated

This is what you declared:
[ptr] [ptr] ... [ptr] //10 of these
[ptr] [ptr] ... [ptr]
[ptr] [ptr] ... [ptr]

Meaning: you didnt allocate space for the the color names. Yet somehow it compiles.

Also, '\0' is a constant.
"this is a string" is a string that has \0 (NULL) after 'g' letter.
a pointer: char *p; can be assigned to point to a string like the string above.
a pointer to char cannot point to a constant but it can have its value for example.

because constant itself is a value, not an adress. pointer's point to an adress, not value.