Computer Science Canada

Accessing a Specific Memory Address
Author:  andytyk [ Mon Jun 21, 2004 8:07 pm ]
Post subject:  Accessing a Specific Memory Address
Given an arbitrary memory location, how do I load the value stored at that address into a variable?

Is it even possible? I've been searching online, but haven't come up with any solutions.
Author:  wtd [ Mon Jun 21, 2004 9:32 pm ]
Post subject: 
code:
int main()
{
   int arbitrary_address = 0x01010101;
   char * ptr = static_cast<char *>(arbitrary_address);
}
Author:  andytyk [ Mon Jun 21, 2004 9:56 pm ]
Post subject: 
Copy and pasted into VC++,

Untitled.cpp(8 ) : error C2440: 'static_cast' : cannot convert from 'int' to 'char *'
Conversion from integral type to pointer type requires reinterpret_cast, C-style cast or function-style cast
Author:  Catalyst [ Mon Jun 21, 2004 10:13 pm ]
Post subject: 
code:
char * ptr = (char*)arbitrary_address;

I'm not sure if thats the proper c++ way to do this, but it works with no problems for me.
Author:  wtd [ Mon Jun 21, 2004 10:24 pm ]
Post subject: 
Catalyst wrote:
code:
char * ptr = (char*)arbitrary_address;

I'm not sure if thats the proper c++ way to do this, but it works with no problems for me.


Yes that does work. That's how I did it initially, then decided to be too smart and replaced it with static_cast without testing it again. Smile
Author:  andytyk [ Mon Jun 21, 2004 10:34 pm ]
Post subject: 
Compiled using VC++ 6, it doesn't run into any problems during compilation, but when it is run, it generates one of those "Report to Microsoft" errors and doesn't return the desired result.

I am merely trying to devise a way to pass values between two programs running concurrently (written in different languages), I was thinking of simply using files, but then I realized memory would be faster. Oh well, I'll work on the disk file implementation then.
Author:  wtd [ Tue Jun 22, 2004 1:08 am ]
Post subject: 
andytyk wrote:
Compiled using VC++ 6, it doesn't run into any problems during compilation, but when it is run, it generates one of those "Report to Microsoft" errors and doesn't return the desired result.


Because you accessed a memory location you're not allowed to access.

andytyk wrote:
I am merely trying to devise a way to pass values between two programs running concurrently (written in different languages), I was thinking of simply using files, but then I realized memory would be faster. Oh well, I'll work on the disk file implementation then.


You could possibly also use sockets and create a simple client/server environment.

If you do try to use a file, you'll need to lock the file when you write to it. Otherwise you'll get two files making changes to the same file at the same time. That leads to pure insanity.

I would have a server program disconnected from any other program you're working on. Other programs would then be able to connect to it and make requests. Sound like a database? That's pretty much what I'm describing.
Author:  andytyk [ Tue Jun 22, 2004 12:20 pm ]
Post subject: 
wtd wrote:
Because you accessed a memory location you're not allowed to access.


Then how do programs such as memory editors (ie. game cheating programs) access and write to the memory of other programs?

I have the file based method up and working so the issue is resolved. But would still like to see an answer to the question above. Smile

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