Reallocation of memory in c++

[amrich2000]

Hi,
Does anyone know a simple way of reallocating memory in c++ apart from using vectors?

Regards,
Am_Rich...!

[AHMEDYO]

HI...

you can use realloc(ptr,Size), if you bas NULL pointer it will work as Malloc and allocate new memory, if you pass valid Pointer it will reallocate it.

note : Realloc will return new pointer for new memory refrence

Best Regards

[weaknessforcats]

you can use realloc(ptr,Size), if you bas NULL pointer it will work as Malloc and allocate new memory, if you pass valid Pointer it will reallocate it.

Do not use realloc(), calloc(), malloc, alloc() or any other C memory function in C++.

These functions do not call your constrcutors and the free() does not call your destructor.

These are C functions and in C you have to do all the memory work and variable initialization manually. This is a big source of error.

To reallocate in C++, allocate a new area the size of the old area plus additional elements. Note that all the constructors are called on the new allocation. Then you copy each element from the old area to the new one.
This wil call the assignment operator on your class.

Finally, you delete the old area and assign the address of the new areas to the pointer to the old area.

Do not do memcpy(), or any other mem...() calls in C++ because these functions will not call constructors or assignment operators or any other overloaded operators.

[AHMEDYO]

Do not use realloc(), calloc(), malloc, alloc() or any other C memory function in C++.

These functions do not call your constrcutors and the free() does not call your destructor.

These are C functions and in C you have to do all the memory work and variable initialization manually. This is a big source of error.

To reallocate in C++, allocate a new area the size of the old area plus additional elements. Note that all the constructors are called on the new allocation. Then you copy each element from the old area to the new one.
This wil call the assignment operator on your class.

Finally, you delete the old area and assign the address of the new areas to the pointer to the old area.

Do not do memcpy(), or any other mem...() calls in C++ because these functions will not call constructors or assignment operators or any other overloaded operators.

Thanx For your reply..

yes i think you are fully right with this, but just these functions is very useful in same sutiation when normal allocation apart from classes, and classes thats have only data and no methods, and no problem when working with it, he didnt specify what type of allocation he need.

Best Regards

[amrich2000]

Hi Gentleman...
Thanks a lot for your concern... Indeed thats what ive been wondering. Can any of you provide me with a slight example of how reallocation can be made possible using the new operator?

Thanking you,
Am_Rich...!

[AHMEDYO]

HI....

this is a simple example to allocate and deallocate memory locations.

int main()
{
 char* String1=new char[]="My String Size="; //allocate new 15 byte
 int* Int1=new int(15);      //allocate new 4 byte integer & assign 15 to it
 char* String=new char[19];     //allocate new 19 byte
 sprintf(String,"%s%i%c",String1,*Int1,0);  //copy string1 & Int1 to String
 delete Int1;         //deallocate 4 bytes integer variable
 cout << String << endl;       //print result
 delete String;         //deallocate String 19 bytes
 return 0;  
}

Best Regards

[amrich2000]

Thank You Ahmedyo...
I'll try modify my program as such.

Kind Regards,
Am_Rich...!

[weaknessforcats]

but just these functions is very useful in same sutiation when normal allocation apart from classes, and classes thats have only data and no methods, and no problem when working with it,

These are C functions. You can't use these if a) you are using classes or structs, b) you are using placement allocation, c) you are managing a private heap, d) you are overloading operator new.

Please stop using these function in C++.

[DrGonzou]

Do not use realloc(), calloc(), malloc, alloc() or any other C memory function in C++.

These functions do not call your constrcutors and the free() does not call your destructor.

These are C functions and in C you have to do all the memory work and variable initialization manually. This is a big source of error.

To reallocate in C++, allocate a new area the size of the old area plus additional elements. Note that all the constructors are called on the new allocation. Then you copy each element from the old area to the new one.
This wil call the assignment operator on your class.

Finally, you delete the old area and assign the address of the new areas to the pointer to the old area.

Do not do memcpy(), or any other mem...() calls in C++ because these functions will not call constructors or assignment operators or any other overloaded operators.

This is very nice, but you didnt wrote nothing helpfull, you are just saying to not use c functions in C++. Try to make some sugestions.

And BTW there is nothon wrong with using c memory functions in C++ for primitive tipes so ........ I dont know what that this is all about.