比较两个字符[C]

Question

I have a struct

struct Human {
    char            *name;
    struct location *location;
    int             cash;
    char            *weapon;

};

and another one:

struct World {
    char                *name;
    char                *weapon;
    int                 price;
};

These are in header files, and included in a .c program.

Question

I want to compare if the weapon is the same as in both locations

What I tried

int compareWeapons(struct bot *b,int whatToGet) // function signature
struct location *l =  b->location;
if ((strcmp(l->weapon,b->weapon) == 0)) { // do stuff }

** Error message I get **

runtime error: load of null pointer of type 'char'

Kindly advise me, how do I compare two char in different struct, if not using strcmp??

Answer 1

The problem in your code is not the strcmp but the null pointer which means that the variable " b "==NULL,so " b " has no " location " attribute and that's where the NullPointerException generates. I may suggest to check how you pass the arguments to your function Use & to pass the address (pointer) of your variable or just the name of your variable if it's a pointer Also I didn't understand the type " bot " and " location " I think you meant " struct Human " not " struct bot " and " struct World " not " struct location " You can name your struct so you don't have to write struct at each declaration

struct World{
//variables
}World;

And then struct World would be the same as just saying World

Answer 2

The problem is not your string compare, it's how you are declaring your structs.

It seems you are using (struct bot *) to reference the (struct Human). In that case it should look:

int compareWeapons(struct World *b, int whattoget);

Additionally your struct location must be initialized or else you are referencing a struct that contains nothing (NULL).

struct location
{
    //your struct variables
};

Below is a link with a basic example on how to initialize a struct, https://www.cs.usfca.edu/~wolber/SoftwareDev/C/CStructs.htm