Assigning A Specific Memory Address from another program, and changing it's value

Question

Recently I've time off of school for a few days and wanted to do a small program(s) experiment in C++ dealing with memory address. I wanted to see is that if a currently running program (Let call it Program A) that created a pointer to an int object in the heap, can be seen by another program and be modified (Program B). So for Program A, this is my basic code: ``` // Program A #include using namespace std; int main() { // Pointer to an int object in the heap int *pint = new int(15); // Display the address of the memory in heap cout << pint << endl; // Display the value stored in that address cout << *pint << endl; return 0; } ``` Output for Program A: ``` 0x641030 15 ``` For Program B, I looked at how to assigned a specific memory address through this link: http://www.devx.com/tips/Tip/14104 The code for Program B is: ``` // Program B #include using namespace std; int main() { // assign address 0x641030 to p int *p = reinterpret_cast< int* > (0x641030); cout <<…

Accepted Answer

The short answer is that different processes use completely different address spaces. Without doing a lot more work, process B can't read or write the memory from process A.

It is possible to do this, in a platform-specific way. Win32 offers functions such as WriteProcessMemory where you can directly poke values into the memory space of another process. Most operating systems offer a shared memory function, with Win32 you can use memory mapped files and Unix flavours typically have some kind of equivalent "mmap" or "shmem" feature.

Assigning A Specific Memory Address from another program, and changing it's value

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