CODEWITHSUNDEEP
c
Karthik Raj Palanichamy
Karthik Raj Palanichamy

Reputation: 519

How to pass an array of strings to a function?

Could anybody please tell me why is the output of both the prints are not same? How to pass an array of strings to a function then?

main()
{
    char b[10][10];
    printf("%p, %p, %p\n", b, b[0], b[9]);
    getStrListFromString(b);
}

void getStrListFromString(char **strList)
{
    printf("%p, %p, %p\n", strList, strList[0], strList[9]);
}

Expected OUTPUT :

0x7fffbe4ecf00, 0x7fffbe4ecf00, 0x7fffbe4ecf5a
0x7fffbe4ecf00, 0x7fffbe4ecf00, 0x7fffbe4ecf5a

Actual Output :

0x7fffbe4ecf00, 0x7fffbe4ecf00, 0x7fffbe4ecf5a
0x7fffbe4ecf00, 0x7fffbe4ecf80, (nil)

Upvotes: 2

Views: 122

Answers (2)

Lundin
Lundin

Reputation: 213678

In addition to the core issue about pointer-to-pointer having absolutely nothing to do with multi-dimensional arrays, your also has various other bugs:

main() // obsolete form of main(), won't compile unless C90
{
    char b[10][10]; // uninitialized
    printf("%p, %p, %p\n", b, b[0], b[9]); // should be void pointers
    getStrListFromString(b); // wrong type of parameter
    // return statement necessary here in C90
}

void getStrListFromString(char **strList) // should not be pointer-to-pointer
{
    printf("%p, %p, %p\n", strList, strList[0], strList[9]); // same issue as in main
}

The fact that this code compiled means that your compiler is either complete crap or incorrectly configured. You need to fix that asap.

Corrected code:

#include <stdio.h>

void getStrListFromString(char strList[10][10])
{
    printf("%p, %p, %p\n", (void*)strList, (void*)strList[0], (void*)strList[9]);
}

int main (void)
{
    char b[10][10];
    printf("%p, %p, %p\n", (void*)b, (void*)b[0], (void*)b[9]);
    getStrListFromString(b);
}

Upvotes: 2

dbush
dbush

Reputation: 223739

Your function expects a char ** but you're passing it a char [10][10]. These are not the same.

An array when passed to a function decayed to a pointer to the first element. So when you pass a char [10][10] (an array of size 10 of char [10]) to a function it decays into a char (*)[10] (a pointer to a char [10].

Change your function to accept either char [10][10] or char (*)[10].

Upvotes: 3

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