In a function declaration, what does passing a fixed size array signify? [duplicate]

Answer 1

The 25 in the parameter declaration is ignored by the compiler. It's the same as if you'd written string ar_dictionary[]. This is because a parameter declaration of array type is implicitly adjusted to a pointer to the element's type.

So the following three function declarations are equivalent:

void read_dictionary(string ar_dictionary[25], int& dictionary_size)
void read_dictionary(string ar_dictionary[],   int& dictionary_size)
void read_dictionary(string *ar_dictionary,    int& dictionary_size)

Even in the case of the first function, with the size of the array explicitly declared, sizeof(ar_dictionary) will return the same value as sizeof(void*).

See this sample on Codepad:

#include 
#include 

using namespace std;

void read_dictionary(string ar_dictionary[25], int& dictionary_size)
{
    cout << sizeof(ar_dictionary) << endl;  
    cout << sizeof(void*) << endl;  
}

int main()
{
    string test[25];
    int dictionary_size = 25;
    read_dictionary(test, dictionary_size);

    return 0;
}

Output (the exact value is, of course, implementation-dependent; this is purely for example purposes):

4
4