C pass array of structs by reference or by value to a function

Question

I have a function in C which takes an array of structs as an argument:

int load_ini_parms(char * ini_file,
                   struct test_object s[],
                   int num,
                   struct lwm2m_object * l)

My question is, would it be better programming practice to pass a pointer to an array of structs? What would be the advantages or disadvantages?

By using struct test_object s[] as argument, the compiler actually sees it as struct test_object *s. So you're already passing a pointer (to the first element). — Some programmer dude
– Some programmer dude, Commented Aug 10, 2017 at 9:10
Passing an array as an argument technically equals passing a pointer to its first element, so if you passed a pointer to an array, you would've simply passed a pointer to a struct pointer, which might be sometimes useful but unnecessary here — Fureeish
– Fureeish, Commented Aug 10, 2017 at 9:11

jfMR · Accepted Answer · 2017-08-10 09:17:04Z

7

It doesn't make any difference because passing an array as a function argument decays into a pointer.

The function

int load_ini_parms(char *ini_file, struct test_object s[], int num, struct lwm2m_object *l)

is equivalent to

int load_ini_parms(char *ini_file, struct test_object *s, int num, struct lwm2m_object *l)

The information regarding to the size of the array is lost in both cases.

edited Aug 10, 2017 at 9:17

answered Aug 10, 2017 at 9:09

jfMR

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Comments

JimmyB · Accepted Answer · 2017-08-10 09:19:49Z

5

Contrary to what others here say, I say it does make a difference as to what may be a "better programming practice":

Declaring the parameter as an array indicates to the user of the function that you expect, well, an array.

If you only declare a pointer this does not tell anyone if you expect a single element or possibly multiple.

Hence, I'd prefer the pointer for single-element parameters (e.g. "output" parameters) and the array for (potentially) multiple elements.

answered Aug 10, 2017 at 9:19

JimmyB

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