Dynamic array of ints problem

[viperdriver87]

Greetings all, I'm working on a program that contains a struct:

struct queue {

int front; //the front of the queue
int elements; //the number of elements in the queue
int asize; //the size of the array
int qlist[]; //an array that will be dynamically sized

};

My objective is to read from a file, the length of the queue. Now, I've tried to use malloc, realloc and sorts of things to resize the array qlist[]. All my attempts have failed. My question: how can I resize qlist[] to store a number of ints specified at runtime?

I'd like to use a pointer to the struct, instead of the struct itself, if possible. Example: struct queue * q, instead of struct queue q;

Thanks in Advance.

[Silent1Mezzo]

Greetings all, I'm working on a program that contains a struct:

struct queue {

int front; //the front of the queue
int elements; //the number of elements in the queue
int asize; //the size of the array
int qlist[]; //an array that will be dynamically sized

};

My objective is to read from a file, the length of the queue. Now, I've tried to use malloc, realloc and sorts of things to resize the array qlist[]. All my attempts have failed. My question: how can I resize qlist[] to store a number of ints specified at runtime?

I'd like to use a pointer to the struct, instead of the struct itself, if possible. Example: struct queue * q, instead of struct queue q;

Thanks in Advance.

If you know the maximum number of elements that qlist can hold then put that within the brackets. If you don't know then do

int* qlist

and then you can malloc it.

[viperdriver87]

If you know the maximum number of elements that qlist can hold then put that within the brackets. If you don't know then do

int* qlist

and then you can malloc it.

Ok, that's not a problem. But, say I do malloc it like this:

struct queue {


int front;
int elements;
int asize;
int * qlist;

};

...

struct queue * resize(int size){

struct queue * q;

q->front = 0;
q->elements = 0;
q->asize = size;
q->qlist = (int *)malloc(sizeof(int) * size);

return q;

}

in the above function, "size" is the max number of elements i'm going to store. If i attempt to what is shown in the code above, I usually get an 'improper use of flexible member' error. Any ideas?

[Silent1Mezzo]

Ok, that's not a problem. But, say I do malloc it like this:

struct queue {


int front;
int elements;
int asize;
int * qlist;

};

...

struct queue * resize(int size){

struct queue * q;

q->front = 0;
q->elements = 0;
q->asize = size;
q->qlist = (int *)malloc(sizeof(int) * size);

return q;

}

in the above function, "size" is the max number of elements i'm going to store. If i attempt to what is shown in the code above, I usually get an 'improper use of flexible member' error. Any ideas?

Because q is a pointer to the structure you need to first malloc that pointer so it has enough room to hold everything inside of it

q = malloc(sizeof(struct queue));

[viperdriver87]

Brilliant! Problem solved, thanks a bunch!

[Silent1Mezzo]

Brilliant! Problem solved, thanks a bunch!

Glad everything worked out for you.