Help with double pointers and const
-
Hi, i cannot figure this out:
typedef struct
{
int a;
int b;
} CARPIC;const CARPIC const* CarPics[] =
{
&Audi,
&BMW,
&Bugatti,
}// Get function
void GetCarPicture(CARPIC** carPicture)
{
int carId= GetCarId(); // Lets say, returns 2
*carPicture = CarPics[carId];
}// Using the function
CARPIC* car;
GetCarPicture(&car);I get the warning:
warning: assignment discards qualifiers from pointer target type
I tried to add the const keyword to the GetCarPicture function parameter but could not figure out where to add it. I need to get the pointer to the const car picture. Regards.
-
Hi, i cannot figure this out:
typedef struct
{
int a;
int b;
} CARPIC;const CARPIC const* CarPics[] =
{
&Audi,
&BMW,
&Bugatti,
}// Get function
void GetCarPicture(CARPIC** carPicture)
{
int carId= GetCarId(); // Lets say, returns 2
*carPicture = CarPics[carId];
}// Using the function
CARPIC* car;
GetCarPicture(&car);I get the warning:
warning: assignment discards qualifiers from pointer target type
I tried to add the const keyword to the GetCarPicture function parameter but could not figure out where to add it. I need to get the pointer to the const car picture. Regards.
This would make more sense: ```c++ typedef struct { int a; int b; } CARPIC; CARPIC Audi = { 1, 2 }; CARPIC BMW = { 1, 2 }; CARPIC Bugatti = { 1, 2 }; CARPIC const* CarPics[] = { &Audi, &BMW, &Bugatti, }; // Get function const CARPIC* GetCarPicture(int carId) { return CarPics[carId]; } // Using the function CARPIC const* car; car = GetCarPicture(2);/// ```
-
Hi, i cannot figure this out:
typedef struct
{
int a;
int b;
} CARPIC;const CARPIC const* CarPics[] =
{
&Audi,
&BMW,
&Bugatti,
}// Get function
void GetCarPicture(CARPIC** carPicture)
{
int carId= GetCarId(); // Lets say, returns 2
*carPicture = CarPics[carId];
}// Using the function
CARPIC* car;
GetCarPicture(&car);I get the warning:
warning: assignment discards qualifiers from pointer target type
I tried to add the const keyword to the GetCarPicture function parameter but could not figure out where to add it. I need to get the pointer to the const car picture. Regards.
-
It should be
void GetCarPicture(const CARPIC const * * carPicture)
{
//...
}
//...
// Using the function
const CARPIC const * car;
GetCarPicture(&car); -
It should be
void GetCarPicture(const CARPIC const * * carPicture)
{
//...
}
//...
// Using the function
const CARPIC const * car;
GetCarPicture(&car);These second
consts don't appear to make sense: both refer to theCARPICvalue, neither refers to the pointer holding the address. That's also what my compiler states (in a warning). To give some examples:const int *a; // pointer to const int
int const *a; // pointer to const int (same as above!)
const int const *a; // warning C4114: same type qualifier used more than once
int *const a; // const pointer to int
const int * const a; // const pointer to const intSee also http://cdecl.ridiculousfish.com/?q=const+int+*+const+*+a%3B[^]
GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)
-
The two
consts are duplicate. Both refer to the CARPIC value. Neither refers to the pointer. You might also want to check out my comment to CPallinis response in this thread.GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)
-
These second
consts don't appear to make sense: both refer to theCARPICvalue, neither refers to the pointer holding the address. That's also what my compiler states (in a warning). To give some examples:const int *a; // pointer to const int
int const *a; // pointer to const int (same as above!)
const int const *a; // warning C4114: same type qualifier used more than once
int *const a; // const pointer to int
const int * const a; // const pointer to const intSee also http://cdecl.ridiculousfish.com/?q=const+int+*+const+*+a%3B[^]
GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)