Is there any difference between these two declarations?

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Difference between passing array and array pointer into function in C

I have been wondering this for a while, is there any difference between these two?

void f1(char *c);
void f2(char c[]);

A common example is this:

int main(int argc, char **argv);
int main(int argc, char *argv[]);

Are there any reasons to prefer one to the other, apart from artistic ones?

http://stackoverflow.com/questions/5573310/difference-between-passing-array-and-array-pointer-into-function-in-c — chepner, Apr 20 '12 at 14:20

score 6 · Accepted Answer · answered Apr 20 '12 at 14:21

6

There is no difference.

From the horse mouth:

(C99, 6.7.5.3p7) "A declaration of a parameter as "array of type" shall be adjusted to "qualified pointer to type", where the type qualifiers (if any) are those specified within the [ and ] of the array type derivation."

On the reasons to prefer one form over the other, it depends on the people. Here is what H&S says (on switching to T *array from T arr[]):

(H&S, 5.4.3 Array Bounds) "That would more accurately reflect the implementation but less clearly indicate the intent."

answered Apr 20 '12 at 14:21

ouah

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Who are H&S? Google isn't very helpful with such a short query. – orlp Apr 20 '12 at 14:24
Harbison & Steele http://careferencemanual.com – ouah Apr 20 '12 at 14:25
[Harbison & Steele](http://careferencemanual.com/). – John Bode Apr 20 '12 at 14:26
Thanks. Would you recommend it to me? (I'm intermediate at C right now). – orlp Apr 20 '12 at 14:26
Totally, it is one the best book around for C. Note that it's a reference book. – ouah Apr 20 '12 at 14:27

score 2 · Answer 2 · answered Apr 20 '12 at 14:19

2

No. In a function declaration/definition, the use of an array as an argument is syntactic sugar only. It's still passed as a pointer, and sizeof(theArgument) will still give you sizeof(TheType *) rather than sizeof(TheType) * sizeof(numElements).

answered Apr 20 '12 at 14:19

Jonathan Grynspan

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score 1 · Answer 3 · answered Apr 20 '12 at 14:19

Well first one indicates that this is a pointer and the second that this is an array. While there is no effective difference, when you read the code you generally expect a single element in the first case an a sequence of more then one element in the second case. This might be helpful sometimes.

score 0 · Answer 4 · answered Apr 20 '12 at 14:20

0

There is no difference. Every n-dimensional array in both C and C++ can be interpreted as both n-dimensional array and pointer to (n-1)-dimensional array (as the pointer's [] semantic is same as array's one).

answered Apr 20 '12 at 14:20

Griwes

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Is there any difference between these two declarations?

4 Answers4