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This article introduces the knowledge about "why C++ cannot assign pointers to derived class arrays to base class pointers". In the actual case operation process, many people will encounter such difficulties. Next, let Xiaobian lead you to learn how to deal with these situations! I hope you can read carefully and learn something!

Never assign a pointer to a derived class array to a base class pointer

Reason

Subscripting the resulting base pointer will lead to invalid object access and probably to memory corruption.

Subscript operations on base class pointers as a result of assignment cause invalid object accesses and possible memory corruption.

Example

struct B { int x; };

struct D : B { int y; };

void use(B*);

D a[] = {{1, 2}, {3, 4}, {5, 6}};

B* p = a; // bad: a decays to &a[0] which is converted to a B*

p[1].x = 7; // overwrite D[0].y

use(a); // bad: a decades to &a[0] which is converted to a B*Enforcement

Flag all combinations of array decay and base to derived conversions.

Prompt for all array degeneration and base class type to derived class type conversions.

Pass an array as a span rather than as a pointer, and don't let the array name suffer a derived-to-base conversion before getting into the span

Use span to pass arrays instead of pointers, and don't let array names undergo a derived class conversion to base class types before placing them in span.

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