Arguments to C program question [duplicate]

This question already has answers here: Closed 11 years ago.

Possible Duplicate:

Should I use char** argv or char* argv[] in C?

What is the difference between using char **argv and char *argv[] for the second parameter to a c program. Does it affect the way the strin开发者_JS百科gs are passed? Thanks :-)

---

There is absolutely no difference. At all.

in C

void f(int*);

and

void f(int[]);

and

void f(int[42]);

are three completely identical declarations.

---

**argv and *argv[] as a function argument are technically identical - as C will convert any array into a pointer in a function argument.

Note that this can catch you out, for example this is totally valid and won't raise any warnings (or errors), even though a beginner might think that the array passed is invalid:

void func(int array[2])
{
    array[1] = 1; // buffer overrun: will write past the end of a[].
}

int main()
{
    int a[1];
    func(a);
    return 0;
}

---

In the context of a function parameter declaration, T a[] and T *a are synonymous. In both cases, a is a pointer to T.

When an array expression appears in a context other than as an operand to the sizeof or unary & operators (such as a parameter in a function call), the type of the expression is implicitly converted from "N-element array of T" to "pointer to T", and the value of the expression is the address of the first element in the array. Thus, a function can never receive an array value; it can only receive a pointer to the first element.

dmr decided to use the T a[] syntax to make the intent clear (a refers to the first element of an array of T as opposed to a pointer to a single instance of T), but I think it's caused more heartburn that it was worth.