How to nullify an array?

Question

having an array:

char* arr[some_size] = {nullptr};

and later initializing some of its elem's is there any way that I can reset this array in other way than iterate over its elements and set them to nullptr?
I would like to avoid this:

for(unsigned i = 0; i < some_size;++i)
{
arr[i] = nullptr;
}

Rob Kennedy · Accepted Answer · 2011-06-17 05:26:29Z

7

You can either iterate over it yourself, or you can call a function that iterates over it for you:

#include <algorithm>

// choose either one:
std::fill_n(arr, some_size, nullptr);
std::fill(arr, arr + some_size, nullptr);

One way or another, iteration must occur.

answered Jun 17, 2011 at 5:26

Rob Kennedy

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3 Comments

smallB Over a year ago

funny that there isn't same way of nullifying array after this array had been initialized. I can do this: T* arr[size] = {nullptr}; but later after this array has been initialized I cannot to arr[size] = {nullptr};

smallB Over a year ago

@Nawaz I'm more than happy to use more modern ver, so in this sense I don't see a problem.

Rob Kennedy Over a year ago

Iteration still occurs when you initialize it, SmallB. It's just that the compiler generates the code for it instead of you or the standard-library authors.

David Cuthbert · Accepted Answer · 2011-06-17 05:34:26Z

4

Rob's answer will work for C++. If you're doing straight up C, look into memset() or bzero().

char *arr[size] = { NULL };
...
memset(arr, 0, sizeof(char *) * size);
/* or */
bzero(arr, sizeof(char *) * size);

memset (standard C) is generally preferred over bzero (being a BSD-ism).

answered Jun 17, 2011 at 5:34

David Cuthbert

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3 Comments

Rob Kennedy Over a year ago

The (minor) problem either of those functions is that we have to assume a null pointer is represented by all-bits-zero, which isn't necessarily the case.

edA-qa mort-ora-y Over a year ago

@Rob, while technically true, can you think of any architecture where it is not zero?

Rob Kennedy Over a year ago

@Eda, please see comp.lang.c FAQ 5.17. They're not common systems, which is why I said this is a minor problem.

C.J. · Accepted Answer · 2011-06-17 05:36:31Z

0

I think that Cuthbert's answer is good. There is also the ZeroMemory WinAPI function (For windows).

answered Jun 17, 2011 at 5:36

C.J.

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