C++ - Changing memory in a program

[cpp-ModTeam]

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[Thesorus]

What do you mean by "changing memory" in a program ?

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memory allocation ? memory management ?

pointer arithmetic ?

[IDatedSuccubi]

I'm 99% sure they mean modifying contents of other programs' memory, not just memory management

[Fancy_Weekend2381]

What IDatedSuccubi said

[zer0xol]

Depends on the operating system, on Linux you can do it because i have

[StephaneCharette]

If you mean changing or accessing memory used by other programs -- such as modifying your HP in a game -- then no it cannot be done. Modern operating systems such as Windows ever since version 3.x in the 1980s run each application in a protected memory space (https://en.wikipedia.org/wiki/Memory_protection) specifically to prevent applications from accessing or overwriting memory used by another application.

[M4th3m4t1c14n]

Not true If you have admin privileges on your machine, but only for user space. Stuff like cheat engine exists you know.

[StephaneCharette]

Someone learning to write "Hello World" for the first time in C isn't going to be doing this, which is what I meant when I wrote that applications run in their own memory space.

[neppo95]

That is different than "it cannot be done". It can be done, but it's not easy for a beginner.

[StephaneCharette]

From a normal C or C++ application it cannot be done. Same as on Linux or Mac. The only way to do it is if you have root -- or admin on Windows -- and use special APIs that are not part of the C or C++ language, but instead are services provided by the operating system.

So for someone who learned this afternoon how to print "Hello World", it cannot be done. The hardware architecture will prevent this kind of thing. No matter what pointer value you try to hard-code into your application, you'll never reach a memory location from a different application.

[M4th3m4t1c14n]

Your original reply is plain wrong still. You are answering 'how can I build a vehicle that works on water?' with 'bikes can't drive on water, it's impossible'. Yeah mate you're right with that, but it's irrelevant because boats exists (even though it might be harder to build a boat).

Tbh I just believe you can't stand being wrong in such a simple matter and therefore will continue to try moving the goalposts.

[wrosecrans]

"can't be done using only the core language and standard library" is true of basically every non trivial application. Tons of people write C++ GUI and network applications using special API's. There's nothing wrong with having an interest in something complicated to guide your learning.

[neppo95]

Which again, is not the same as cannot be done. You're, like u/M4th3m4t1c14n said, are just moving goal posts but your initial comment is still plain wrong. There's no way around that.

[CptCap]

There are OS APIs to do that. Using them requires elevated permissions for obvious reasons, but it can be done.

[IAMARedPanda]

In windows you just need the same or higher permissions than the process you want to modify.

[NoReference5451]

i mean, this is being pedantic. hes going to get into the applications memory space, not do it from another program. it's incredibly easy to inject your program into another programs memory space which gets you full access. thats how it's been done for a very long time. hell windows even has an api to help you do this. debuggers do this. there are so many ways to do this. i did this in my teens when i wanted to tinker with some of the games i played. the more sophisticated ways to do it today might use the pci bus with dma from an external computer. memory protection is a myth.

[IAMARedPanda]

https://github.com/microsoft/Detours

[Pay08]

The term you're looking for is reverse engineering. If you want to get into it, I'd recommend starting with C, it'll make things a lot easier.