Array syntax vs. pointer syntax in C function parameters

Question

I understand how arrays decay to pointers. I understand that, for the compiler, this:

void foo(int *arg1);

is 100% equivalent to this:

void foo(int arg1[]);

Should one style be preferred over the other? I want to be consistent, but I'm having a hard time justifying either decision.

Although int main(int argc, char *argv[]) and int main(int argc, char **argv) are the same, the former seems to be much more common (correct me if I'm wrong).

Answer 1

I would recommend against using the [] syntax for function parameters.

The one argument in favour of using [] is that it implies, in a self-documenting way, that the pointer is expected to point to more than one thing. For example:

void swap(int *x, int *y)
double average(int vals[], int n)

But then why is char * always used for strings rather than char [] ? I'd rather be consistent and always use * .

Some people like to const everything they possibly can, including pass-by-value parameters. The syntax for that when using [] (available only in C99) is less intuitive and probably less well-known:

const char *const *const words vs. const char *const words[const]

Although I do consider that final const to be overkill, in any case.

Furthermore, the way that arrays decay is not completely intuitive. In particular, it is not applied recursively ( char words[][] doesn't work). Especially when you start throwing in more indirection, the [] syntax just causes confusion. IMO it is better to always use pointer syntax rather than pretending that an array is passed as an argument.

More information: http://c-faq.com/~scs/cgi-bin/faqcat.cgi?sec=aryptr#aryptrparam .

Answer 2

Except for char* , I use Type array[N] , where N is some number or a defined constant, when the passed item conceptually is an array (ie, it contains N>1 elements), Type * pointer when the passed item is a pointer to exactly one object.

I tend to use std::vector if the array is of a variable size. C99's concept of variable sized arrays is not available in C++.