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I have an array:
int array[50];
I want to null all the positions in the array because I will be copying some stuff later into it, but at the same time, not all the positions maybe filled. So later when I do a check to see how many integers are in there I can be assured that the checking will stop when it encounters a NULL.
However when I do try to assign NULL
array[n++] = NULL;
I get warning assignment makes integer from pointer without a cast.
What do I do?
Initialise the array to zeroes
Of course, this implies that you cannot store zeroes in the array. An alternative is to have a counter keep track of how many elements are in use, but then you must use elements contiguously.Code:int array[50] = {0};
Ah...heheQuote:
Originally Posted by laserlight
Or, if you need to do it again on an existing array, memset() is the function to use:
--Code:#include <stdlib.h>
...
memset(array, 0, sizeof(array));
...
Mats
memset? Never heard of it, but I'll check it up, sounds useful.
Thanks laser and mats
Here's the description:
http://www.hmug.org/man/3/memset.php
Edit: Also, NULL should be used ONLY on pointer variables - integer arrays should contain 0 (zero), NULL is "never" the right value for an integer - particularly in C (in C++ NULL is actually defined as 0, so it should make no difference to 0, but the meaning is stilll [of sorts] a NULL pointer).
--
Mats
Err, I did that that initialize to 0 thing and it gave me 150 errors, quite literally.
Could it be because this array is declared inside a struct?
You did WHAT?
Yes, initializing an array inside a struct would be something like:
--Code:struct a
{
int array[50];
int x;
float f;
};
struct a somevar = { { 0 } , 7, 13.5f }; // Array set to all zeros, x = 7, f = 13.5
Mats
Ok, I'll try that, but I really didn't think that it would bring up so many errors
No that didn't work. However I tried initializing it in a function instead,
That quite literally gave me 100's of errors too.Code:if (x >= 19) {
h->array[A] = {0};
}
Oh no wait, hang on that did work, but it takes me back to square one, integer from pointer without a cast warning
When you get "150 errors" from one small change, it's usually because the compiler got completely confused, and lost track of what it was doing, and then "everything" generates an error, because it's all "out of place".
I liken this with when you tell someone that they should turn right after the big tree, then take the first left, and someone has cut down and removed the tree you referred to, so the person following your directions will drive way past the first turning, and then be completely lost at the point when the person actually finds a turning next to a big tree. Likewise, if the compiler gets confused by certain things and "takes the wrong turning", it can be VERY easy to run up hundreds of errors, because it's just lost the plot completely.
--
Mats
Nah, your struct initializer method worked, but it still gives the warning I had to begin with.Quote:
Originally Posted by matsp
As a matter of fact, it compounds the error, because I got a pointer array and it's giving me a warning for that as well. Isn't there a way to change just one variable in a struct without needing to include others?
What's A - and you probably shouldn't have a {0} there - this is not a initialization of a variable, it's an assignment - so the you can't/shouldn't use braces here - it will just cause the compiler to get confused.Code:if (x >= 19) {
h->array[A] = {0};
}
--
Mats
A is #defined to be 50Quote:
Originally Posted by matsp
But I like that struct initializing method instead of calling in a function, how do I use that for modifying just one specificied member? Tried nulling the remaining members but some are arrays with pointers and it gives all sorts of errors
And that's presumably the size of the array?
You can't do that. Initialization like was suggested early on in this thread is ONLY possible when you declare the variable itself.
If, inside the code, you need to fill the array with a value (such as zero), then memset is the option.
--
Mats
Ah memset, that seemed to work, thanks !
Boom! Buffer overflow!Quote:
Originally Posted by JFonseka
You are using the index operator to access the 51th element there. And ONLY that element to boot, nothing else.
Be careful with those arrays! Buffer overruns are very bad.
All arrays goes from 0 to size - 1.
Yea well in my program I didn't have it as 50, I had it at 1000, I was just using random numbers, lol.Quote:
Originally Posted by Elysia
OK, so you avoided a buffer overrun. That's good :)
But using random numbers everywhere doesn't make much sense, does it?
I just gave it 1000 because I knew there was no way 1000 elements would be usedQuote:
Originally Posted by Elysia