Reading particular memory location ?

This is a discussion on Reading particular memory location ? within the C Programming forums, part of the General Programming Boards category; Hi members, Now a days i was working on a program and i made a big move in it. Now ...

  1. #1
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    Reading particular memory location ?

    Hi members,
    Now a days i was working on a program and i made a big move in it. Now the last stage is that i came up with a memory address and i wanna read the content at that particular address.. I have got the memory location and i simply made a "long int" variable and tried to read that memory location but error in program. Here is my source code.
    Code:
    #include<stdio.h>
    int main()
    {
         long int *a;
         a=58112;
         printf("%ld",*(58112));
         getchar();
         return 0;
    }
    I think that we can't assign a constant to a pointer. Am I right ? If yes then please tell me how can i read this particular memory location.Alll suggestions are welcomed.

    With love
    REAL NAPSTER

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    Code:
    *((long int *)58112)
    perhaps?

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    Devil's Advocate SlyMaelstrom's Avatar
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    You can't just assign any random memory address to a variable. First off, you couldn't possibly know if that memory address was even reserved for your program. What you have there would give you a segmentation fault for accessing memory outside of the programs scope.

    Why would you want to read a memory address if you don't know what's there, anyway?
    Sent from my iPadŽ

  4. #4
    ZuK
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    Code:
     printf("%ld",*a);
    or
    Code:
         printf("%ld",*(long *)58112);
    should "work".
    Kurt

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    Devil's Advocate SlyMaelstrom's Avatar
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    Work as far as what? Compile?

    Compilation errors on only the beginning of the OP's problems with this code.
    Sent from my iPadŽ

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    ZuK
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    Quote Originally Posted by ZuK
    [should "work".
    as for your question yes compiles. I don't question the origin of the magic number.
    Kurt

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    Your code eliminated the errors and i was able to make exe. But when i executed that some error came up and that was :
    Code:
    The instruction at "0x00401309" referenced memory at "0x037c0000".The
    memory could not be "read".
    
    click on OK to terminate the program.
    click on CANCEL to debug the program.
    By the way thanks guys but still the problem is here.

    With thanks
    REALNAPSTER

  8. #8
    and the hat of wrongness Salem's Avatar
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    > The instruction at "0x00401309" referenced memory at "0x037c0000".The
    > memory could not be "read".
    Try listening to SlyMaelstrom
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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    Devil's Advocate SlyMaelstrom's Avatar
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    Let's make pictures. They're fun and easy to understand.
    Attached Images Attached Images  
    Last edited by SlyMaelstrom; 05-03-2006 at 06:59 AM.
    Sent from my iPadŽ

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    Supermassive black hole cboard_member's Avatar
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    >> I AM NOT A COMPILER. PLEASE DO NOT TREAT ME LIKE ONE.

    I don't scream obscenities at you when you fail to compile or fiddle with your libraries do I?
    Did you draw that picture yourself?
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

  11. #11
    Devil's Advocate SlyMaelstrom's Avatar
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    Quote Originally Posted by ahluka
    >> I AM NOT A COMPILER. PLEASE DO NOT TREAT ME LIKE ONE.

    I don't scream obscenities at you when you fail to compile or fiddle with your libraries do I?
    Did you draw that picture yourself?
    Yes you do and yes I did.
    Sent from my iPadŽ

  12. #12
    Supermassive black hole cboard_member's Avatar
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    Sorry if I broke anything.
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

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    hi guys,
    I used this code to read the memory addresses and i can read only a specific range.
    Code:
    #include<stdio.h>
    int main()
    {
        printf("%ld",*(long int *)2281471);
        getchar();
        return 0;
    }
    The address range is
    minimum = 2281472
    maximum = 2297852
    Now i wanna know if i can read this region why i can't read the region that i want ? Actually i wanna read "address : 1613758136". Please tell me what the hell is happening beyond this specific region ?

    what i can say know i just why why why why........... ?

    A plethora of questions and no answer. Why but why i can't read that address ? There should be some way.

    Thanks skymaelstrom for telling me the internal memory management.


    With happiness
    real napster
    Last edited by realnapster; 05-03-2006 at 11:12 AM.

  14. #14
    Devil's Advocate SlyMaelstrom's Avatar
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    What part of
    Quote Originally Posted by SlyMaelstrom
    What you have there would give you a segmentation fault for accessing memory outside of the programs scope.
    don't you understand?

    Any of your major operating systems have this very basic security that prevents an executable from accessing memory outside of its scope. This is so applications can't edit other applications (without of course the other application accepting the data). More specifically, the OS puts it in place so you can't edit system memory and system applications, meaning to say, in Windows for example, you can't mess with explorer.exe, svchost.exe, etc...

    So, to put it plain and simple... you can't access memory outside of your programs scope. Which means you can just access some arbitrary memory address. The only way you could would be considered hacking, which is not discussed on these forums. So please... stop whining.
    Sent from my iPadŽ

  15. #15
    and the hat of wrongness Salem's Avatar
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    You can't access memory you don't own - period.
    If you try it, the OS kills your program - period.

    Picking random memory addresses doesn't work, something (namely the OS) has to tell you which bits of memory you can access and which you can't.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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