C traps and defects Chapter 3 semantic "traps" 3.3 array declaration as parameters

Array declaration as a parameter
stay C In language , We cannot pass an array directly as a function parameter . If we take the array name as a parameter , Then the array name is immediately converted to point to the... Of the array 1 Pointers to elements . for example , The following statement ：
char hello[] = "hello";
hello It's an array of characters . If you pass this array as a parameter to a function ： 
printf("%s\n", hello);
In fact, it is the same as that of the array 1 The parameter addresses of elements are completely equivalent as parameters passed to functions , namely
printf("%s\n", &hello[0]);
therefore , There's no point in using arrays as arguments to functions . therefore ,C The language will automatically convert the array declaration as a parameter into the corresponding pointer declaration . in other words , Writing like this ： 
int strlen(char s[]) {
    /* The specific content */ 
}
It is exactly the same as the following ： 
int strlen(char *s) {
    /* The specific content */ 
}

extern char *hello;
This statement is very different from the following statement ： 
extern char hello[];
If a pointer parameter does not actually represent an array , Even if it is technically correct , Array notation is often misleading . If a pointer parameter represents an array , What happens sometimes ？ A common example is function main Second parameter of ： 
int main(int argc, char *argv[]) {
    /* The specific content */ 
}
This kind of writing is completely equivalent to the following writing ： 
int main(int argc, char **argv) {
    /* The specific content */ 
}
It should be noted that , The emphasis of the former writing is argv Is a pointer to the starting element of an array , The elements of this array are of character pointer type . Because these two ways of writing are equivalent , Therefore, readers can choose a writing method that can best reflect their intentions .