pointer to pointer to const
Morten Frederiksen
int a = 42;
int* b = &a;
const int** c = &b; // error
I get "invalid conversion from `int**' to `const int**'" from the
compiler. Logically there should not be a problem, so perhaps it is a
limitation on the compiler.
Regards
Morten Frederiksen
Max M.
> int a = 42;
> int* b = &a;
> const int** c = &b; // error
>
> I get "invalid conversion from `int**' to `const int**'" from the
> compiler. Logically there should not be a problem, so perhaps it is a
> limitation on the compiler.
Logically there *is* indeed a problem. If that assignament were possibile,
you could change the content of 'b' by assigning a value to '*c'. Since
'*c' is of type 'const int*', 'b' could end up pointing to a 'const int'.
Max
Peter Julian
"Morten Frederiksen" <nos...@nospam.nospam> wrote in message
news:4294d9f3$0$306$ba62...@nntp05.dk.telia.net...
The compiler behaves as expected.
Because the constant keyword used above implies a constant value, not a
constant pointer. Since variable a is mutable, the pointer to a constant
can't bind to it.
Note:
#include <iostream>
int main()
{
const int aa = 11;
const int bb = 22;
const int *p_a = &aa;
const int *p_b = &bb;
const int **pp_c = &p_b;
*pp_c = p_a; // ok !, mutable pointer
// **pp_c = 23; // error... const object
std::cout << "**pp_c = " << **pp_c;
return 0;
}
and...
#include <iostream>
int main()
{
int aa = 11;
int bb = 22;
int *p_a = &aa;
int *p_b = &bb;
int * const * const pp_c = &p_a;
// **pp_c = &p_a; // error... const ptr to a const ptr
// *pp_c = p_b; // error... const ptr
**pp_c = 12; // ok !, mutable object
std::cout << "**pp_c = " << **pp_c;
return 0;
}
V
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Heia...........Heida pilk peale nendele............
Postita ka midagi sinna.
Siis pärast hea mul lugeda, et mu lehtedel on mõni külastaja ka !
red floyd
https://stackoverflow.com/questions/19209882/c-cannot-convert-from-int-to-const-int
David Brown
> On 7/14/2023 6:11 PM, V wrote:
>> Morten Frederiksen kirjutas kolmapäev, 25. mai 2005 kl 23:02:58 UTC+3:
>>> Can anyone explain why this does not work?
>>> int a = 42;
>>> int* b = &a;
>>> const int** c = &b; // error
>>> I get "invalid conversion from `int**' to `const int**'" from the
>>> compiler. Logically there should not be a problem, so perhaps it is a
>>> limitation on the compiler.
>>> Regards
>>> Morten Frederiksen
>
> No, it's a feature of the language. Google for this error, or
> https://stackoverflow.com/questions/19209882/c-cannot-convert-from-int-to-const-int
>
spammer and a Usenet vandal, who spends his time annoying people and
discussion forums. One of his habits is making idiotic replies to
ancient posts.
So while Morten Frederiksen was undoubtedly genuinely interested in an
answer to his original question in 2005, I do not believe he is still
waiting for the answer today.
Many people filter out posters like "V", though vandals like him
regularly change their posting nyms and addresses. By replying to his
post (especially without snipping), you are circumventing these filters
and spreading his spam to people who otherwise manage to avoid it. So
please do not do this.
red floyd
[redacgted]
> regularly change their posting nyms and addresses. By replying to his
> post (especially without snipping), you are circumventing these filters
> and spreading his spam to people who otherwise manage to avoid it. So
> please do not do this.
>
