[C# Request] Fix a pointer over runtime

[Frosttall]

Hey guys,

As you know are pointers in C++ static and won't be moved in the physically memory because it's an unmanaged language. There wouldn't be a problem to read where the pointer points to, store it somewhere else and 5 minutes later would the pointer still point to the same memory location and we wouldn't run in any problems.

I'm trying to achieve now the same with C#, but as it's a managed language does the CLR move the values in the memory as it wishes and the pointed location would change while runtime.
To keep a value physically at the same location while the execution of some code you could use the fixed-Keyword and do your work inside the braces, but the CLR would be able to move the value again as soon as it leaves the code which is "fixed".

My problem is that I want to work with that pointer at various locations and the using of the fixed-Keyword is not possible.

Do you know a way to keep a value the whole runtime physically at the same location?


Thank you!

[Sychotix]

I have no idea what you are talking about...

From what I can tell, you are asking how you can make a pointer point to the same area in memory throughout the entire execution. I don't think this is different in any language. Its just

char *c = malloc(sizeof(char));

Now whatever you store into the memory location allocated for c should be there forever, as long as no other piece of your code (or outside malicious code) changes that. Afaik, the address at which the pointer is stored should not change either. It wouldn't make sense for program to continually copy/move the data to different locations.

EDIT: Forgot to add the exception that if you lose a reference to this location in memory, some languages include a garbage collector which will free the memory for you. I.E. Java/Python

[TOM_RUS]

You can try GCHandle Structure with GCHandleType.Pinned. What kind of information your pointer points to?

P.S. An instance with nonprimitive (non-blittable) members cannot be pinned this way.

[Frosttall]

I have no idea what you are talking about...

From what I can tell, you are asking how you can make a pointer point to the same area in memory throughout the entire execution. I don't think this is different in any language. Its just

char *c = malloc(sizeof(char));

Now whatever you store into the memory location allocated for c should be there forever, as long as no other piece of your code (or outside malicious code) changes that. Afaik, the address at which the pointer is stored should not change either. It wouldn't make sense for program to continually copy/move the data to different locations.

EDIT: Forgot to add the exception that if you lose a reference to this location in memory, some languages include a garbage collector which will free the memory for you. I.E. Java/Python

You know that I'm talking about C#, do you?

You can try GCHandle Structure with GCHandleType.Pinned. What kind of information your pointer points to?

P.S. An instance with nonprimitive (non-blittable) members cannot be pinned this way.

That's exactly what I'm looking for

I plan to use this for objects, for strings and for ints. I'll try it now but it seems like that it will work.

[Sychotix]

You know that I'm talking about C#, do you?

Yes... but I was just stating that it should not matter what language you are using.

I plan to use this for objects, for strings and for ints. I'll try it now but it seems like that it will work.

If you create a pointer to an integer, the location of that integer should never change unless you tell it to.

For example (using C code because its easiest),

int *x;
x = malloc(sizeof(int));
*x = 42;
int i;

//Assume the pointer x was allocated at memory location 0x0, the malloc call allocated memory at 0x4
//This should print the values 0 4 42
for(i=0;i<however_long_you_want);i++) printf("Address of x: %d Address of value stored in x: %d Value stored in x: %d \n", &x, x, *x);

x = malloc(sizeof(int));
//In C#, the garbage collector as I understand it will (on its next cycle) see that you no longer have a reference to the address at which 42 was stored, so it will free that memory.

*x = 400;
//Assume the garbage collector has not run yet however, so the memory at 0x4 still exists. The new address where the integer is stored is at 0x8
//This should print 0 8 400
for(i=0;i<however_long_you_want);i++) printf("Address of x: %d Address of value stored in x: %d Value stored in x: %d \n", &x, x, *x);

Unless I'm missing some fundamental difference that C# has over any other language I've programmed in (C,C++,C#,Java,Python,Delphi), there is no reason any of the values should be changing.

Now for example, if you are looking at memory within WoW instead of your own program, you may not have the base pointer. WoW (and all programs really) need to know where everything is, even if it is buried within tons of structures/classes.

[Frosttall]

Thank you, indeed would that work in an unmanaged language, but C# isn't

The Garbage Collector of C# trys to keep the heapsize as small as possible. That's why once allocated values won't be stored the whole at the same location, but moved if necessary.

[DarkLinux]

Set that area to non writable. See if that works... I have no idea .. I dont use C#...

[Jadd]

This is what you want: Pinned Object - CodeProject