| Author |
Message |
yancheng.cheok@gmail.com
*nix forums beginner
Joined: 05 May 2006
Posts: 4
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 Posted: Fri Jul 21, 2006 1:17 am Post subject:
determine pointer to point to array or single item during runtime
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hello, may i know how i can determine whether a pointer is pointing to
an array or a single item during runtime?
this is because in certain situation, i need to determine whether to
use delete or delete[] to deallocate the item(s) ponting by the
pointer.
also, is there any way to determine whether the allocated memory
pointed by the pointer is allocated through new or c version calloc/
malloc?
thank you. |
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Victor Bazarov
*nix forums Guru
Joined: 07 Apr 2005
Posts: 3949
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| Posted: Fri Jul 21, 2006 1:26 am Post subject:
Re: determine pointer to point to array or single item during runtime
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yancheng.cheok@gmail.com wrote:
| Quote: | hello, may i know how i can determine whether a pointer is pointing to
an array or a single item during runtime?
|
There is no portable way.
| Quote: | this is because in certain situation, i need to determine whether to
use delete or delete[] to deallocate the item(s) ponting by the
pointer.
|
If it's you who allocated it, you know how to delete it. If it's not
you who allocated it, you shouldn't be responsible for deletion.
| Quote: |
also, is there any way to determine whether the allocated memory
pointed by the pointer is allocated through new or c version calloc/
malloc?
|
No, not portably. In most cases the developers decide to only use
one method. I say, use 'new' and don't concern youself with anything
else.
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask |
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Frederick Gotham
*nix forums Guru
Joined: 09 Jun 2006
Posts: 502
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| Posted: Fri Jul 21, 2006 3:29 am Post subject:
Re: determine pointer to point to array or single item during runtime
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posted:
| Quote: | hello, may i know how i can determine whether a pointer is pointing to
an array or a single item during runtime?
|
The language provides no such facility built-in.
You would have to keep track of it yourself.
| Quote: | this is because in certain situation, i need to determine whether to
use delete or delete[] to deallocate the item(s) ponting by the
pointer.
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A look-up table of some sort. Or perhaps, instead of a pointer:
template <class T>
struct DynmPtr {
T *const p;
bool is_array;
};
| Quote: | also, is there any way to determine whether the allocated memory
pointed by the pointer is allocated through new or c version calloc/
malloc?
|
The language provides no such facility.
You would have to keep track of it yourself.
--
Frederick Gotham |
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Julián Albo
*nix forums Guru Wannabe
Joined: 24 Feb 2005
Posts: 213
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| Posted: Fri Jul 21, 2006 6:39 am Post subject:
Re: determine pointer to point to array or single item during runtime
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yancheng.cheok@gmail.com wrote:
| Quote: | hello, may i know how i can determine whether a pointer is pointing to
an array or a single item during runtime?
this is because in certain situation, i need to determine whether to
use delete or delete[] to deallocate the item(s) ponting by the
pointer.
|
You can avoid the need to determine that by allocating an array of one
element when you want a single item and always using delete [].
--
Salu2 |
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sandy
*nix forums beginner
Joined: 07 May 2005
Posts: 40
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| Posted: Fri Jul 21, 2006 8:34 am Post subject:
Re: determine pointer to point to array or single item during runtime
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some compilers internally call malloc when u use "new" to allocate
memory.
I dont think u might be able to detect whether memory is allocated
using new or malloc during run time.
--
sandeep nitta
Julián Albo wrote:
| Quote: | yancheng.cheok@gmail.com wrote:
hello, may i know how i can determine whether a pointer is pointing to
an array or a single item during runtime?
this is because in certain situation, i need to determine whether to
use delete or delete[] to deallocate the item(s) ponting by the
pointer.
You can avoid the need to determine that by allocating an array of one
element when you want a single item and always using delete [].
--
Salu2 |
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peter.koch.larsen@gmail.c
*nix forums Guru Wannabe
Joined: 21 Jul 2005
Posts: 204
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| Posted: Fri Jul 21, 2006 11:47 am Post subject:
Re: determine pointer to point to array or single item during runtime
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yancheng.cheok@gmail.com wrote:
| Quote: | hello, may i know how i can determine whether a pointer is pointing to
an array or a single item during runtime?
|
You can't do so in the general case, but if you stick to a single
healthy rule, your problem is easily solved: simply don't use new[].
new[] really is not needed as there is a far better substitute using
std::vector.
| Quote: |
this is because in certain situation, i need to determine whether to
use delete or delete[] to deallocate the item(s) ponting by the
pointer.
also, is there any way to determine whether the allocated memory
pointed by the pointer is allocated through new or c version calloc/
malloc?
|
Nope. new could easily just call malloc.
/Peter |
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