Passing array pointer to struct and acces the array

Question

I need to store a pointer to a char array in a struct, and then modify/access the arrays content. How can I do that?

I can only think of something similar to this, but I don't get to the complete compilable solution.

struct foo {
    unsigned char *array;
};

And then:

unsigned char array[512];
struct foo *foo;
foo->array = array;

In another function which receivers pointer to struct:

*(foo->array[0]) = 'K';

If you plan to store a null-zerminated string in the char array, use char instead of unsigned char. — ThiefMaster
– ThiefMaster, Commented Jun 9, 2012 at 0:16

ThiefMaster · Accepted Answer · 2012-06-09 00:00:09Z

3

Your code is almost fine:

foo->array[0] = 'K';

The problem with your code *(foo->array[0]) is that you try to dereference a char which is not even a pointer.

You also need to allocate memory for the struct - currently foo points to some random memory location where an access will most likely crash your program:

struct foo *foo = malloc(sizeof(*foo));

answered Jun 9, 2012 at 0:00

ThiefMaster

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3 Comments

Joel Bodenmann Over a year ago

Aye, I knew that I was near to the solution. Thanks for your help! I know about the malloc, I am using that but just left it blank for not overflooding my question. Thanks for the hint anyways!

Joel Bodenmann Over a year ago

shouldn't it be: malloc(sizeof(foo)); ?

ThiefMaster Over a year ago

@Tectu: from foo being a pointer to struct foo the following the following assumptions are valid: the type of *foo is struct foo and thus sizeof(*foo) == sizeof(struct foo). Using *var avoids having to write the name of the struct again.

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