How to recover an object from a pointer by passing it an hex address? [duplicate]

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• C++ - Get value of a particular memory address 1 answer

Pointers store memory addresses:

int val = 42;
int *p = &val;

Dereference operator recover objects:

std::cout << *p << std::endl;

42

Say that the val's memory address is:

std::cout << p << std::endl;

0x7fff9b2c9794

If I need read what is in a certain memory address?:

int *memAdd = 0x7fff9b2c9794;
std::cout << *memAdd << std::endl;

Error:

error: invalid conversion from ‘long int’ to ‘int*’ [-fpermissive]

How can I do that?