CODEWITHSUNDEEP
carrayspointersstruct
lucia de finetti
lucia de finetti

Reputation: 219

Oddity when declaring an array of structs in C

Basically I have something like this in my code

struct connComp {
  struct connComp *parent;
  struct connComp *neigh[noNN];
  int *pSpinValue, SpinValue, Flag;
  unsigned int size;
} comp[N];

and when I try to use the array of structures comp[N] as input to a function of the type void function(struct connComp) by writing function(comp) in my code, I receive the following error from gcc compiler:

incompatible type for argument 1 of ‘function’ function(comp)

expected ‘struct connComp’ but argument is of type ‘struct connComp *’

So it looks like comp[N] was declared as a pointer and I really cannot figure out why. Thanks very much in advance for any help!

Upvotes: 2

Views: 59

Answers (2)

MoxieBall
MoxieBall

Reputation: 1916

Passing pointers and arrays to a function and C is equivalent. comp is an array of N connComp structs. When you pass comp to the function you have the address of the start of the array, which behaves in the same way a pointer does. To use comp in a function that expects the struct, you have to dereference the pointer - try passing in comp[0].

Upvotes: 2

tdk001
tdk001

Reputation: 1024

An array in C is a pointer. Specifically, to the first element of the array.

To pass a single element to your function, you need to specify which element that is. e.g.

function(comp[2]);

If you want to work on the entire array in your function, you need to change the function to accept an array of your struct, or a pointer to your struct. e.g.

void function(struct connComp[N]); /* to receive an array of a static size */
void function(struct connComp*);   /* to receive an array of a variable size */

Upvotes: 1

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