Quote:warning: ‘sizeof’ on array function parameter ‘strArr’ will return size of ‘std::__cxx11::string* {aka std::__cxx11::basic_string<char>*}’ [-Wsizeof-array-argument]
std::cout << sizeof(strArr) << std::endl;

(Apr 14, 2020 11:48 AM)♣ SoFt ♣ Wrote:  I'm trying to find the length of an array of strings.
Let's say I have this :

Code

string my_str[] = {"a", "b", "c", "d", "e", "f"};

In order to get the length of my_str, I can do:

Code

int n = sizeof(my_str) / sizeof(my_str[0]);

And everything works fine. But if I try to do that in a function, it doesn't work. Like this:

Code

void myfct(string strArr[]) {
int n = sizeof(strArr) / sizeof(strArr[0]);
cout << n;
}

int main() {
string my_str[] = {"1", "2", "E", "E", "1", "E"};
myfct(my_str);
}

I get 0.

So I would like to know why this happens and how else I can do this.

(Apr 14, 2020 01:20 PM)akali Wrote:  sizeof(array) is done at compile time. Otherwise it would give you pointer size. Whenever you're dealing with pointers to arrays, the size needs to be passed as an argument as well. They do not know their own size.

(Apr 14, 2020 01:31 PM)♣ SoFt ♣ Wrote:  So you're saying there is no way for my function to know the length of the array without me passing it as an argument. Right?

(Apr 14, 2020 01:56 PM)creki Wrote:  

gay but works

(Apr 14, 2020 01:56 PM)creki Wrote:  

gay but works

(Apr 14, 2020 01:58 PM)♣ SoFt ♣ Wrote:  You don't necessarily get empty if you exceed the index, do you?
I.think you just get whatever is in the memory

(Apr 18, 2020 07:42 PM)dracx Wrote:  Well am not sure bout those C++ string, butnin C char array, you simply have to loop over the starting address then stop counting the first time you hit a null byte. This is not the case for wide char array tho, each wide char array is composed of two bytes and is terminated by two nill bytes too. Am on mobile so cant properly supply at least some pseudo-code. Google "custom strlen".

(Apr 23, 2020 11:28 AM)zNinja Wrote:  Well, C string(char array) is a little bit tricky, if you have const char array, you can get size easy.  For pointer you can not use "null byte" as orientation, since array can contain binary content which can have multiple null bytes.
You must track size of array trough code, Like when you reading from a file with C api, you must retrieve size of file then allocate container (char array) and then read.