stdlib.h not working as intended with atoi() function

Question

In my program, i'm using the atoi() function to extract an int from argv. When I use

#include <stdlib.h>

I get the following error:

cachesim.c:20: warning: passing argument 1 of ‘atoi’ from incompatible pointer type

However, if I do not include the stdlib.h I receive no error at all and my code functions properly. Why is this?

#include <stdlib.h>
#include <stdio.h>

main(int argc, int **argv){

    if(argc == 0){
            int blk = 32;

            int i;
            for (i = 1; i < argc; i++){
                    if (strcmp(argv[i], "-b") == 0){

                            if (i + 1 <= argc - 1)
                                    blk = atoi(argv[i+1]);
                    }

            }
    } }

The declaration for main should be: main(int argc, char *argv[]){ -- and the warning is because atoi takes char * and not int *... when you don't include the header, the compiler should at least be emitting warnings about undefined function atoi. — JohnH
Notice that "I get the following error:", is followed by a warning achesim.c:20: warning: passing argument ...? This hints,that without proper prototypes found in the include files, the program may compile and run: run correctly or maybe not. — chux - Reinstate Monica

ouah ouah · Accepted Answer · 2014-04-15T18:16:28

Change:

main(int argc, int **argv){

to

int main(int argc, char *argv[]){

Your former declaration is not an acceptable declaration for main and atoi requires a parameter of type char *.

stdlib.h not working as intended with atoi() function

2 Answers