error signal handling

This is a discussion on error signal handling within the C Programming forums, part of the General Programming Boards category; Hello boys! I've got a problem with the handling of OS signal error while opening non-existing files... Look at my ...

  1. #1
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    Question error signal handling

    Hello boys!
    I've got a problem with the handling of OS signal error while opening non-existing files... Look at my little program I've attached: it tries to open a file which doesn't exist (I want to update it, so I used "r+"); Windows gives an error signal (invalid access memory), so I wrote a function to handle it (signal_handler). But if the user chooses to continue after the error, Windows keeps giving the error signal, so the program enters into a sort of infinite cycle!
    How can I do to continue the execution normally?!
    Thanx...
    Attached Files Attached Files

  2. #2
    ATH0 quzah's Avatar
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    Your problem is you're calling 'fclose' on a null pointer. Bad.

    Quzah.
    Hope is the first step on the road to disappointment.

  3. #3
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    Code:
    FILE * Tmp;
    FILE * Tmp2;
    if ((Tmp = fopen("foo.txt", "r+")) == 0)
    {
    	/* file doesn't exist, open and write to it */
    	Tmp2 = fopen("foo.txt" "a");
    	/* write to file here */
    }
    else
    {
    	/* file exists, uh oh */
    }
    fclose(Tmp);
    fclose(Tmp2);
    return 0;
    > it tries to open a file which doesn't exist (I want to update it, so I used "r+");
    How do you "update" a file that doesn't exist?

    I think you could find this information in any decent tutorial by searching google.
    Last edited by Shadow; 04-29-2002 at 03:22 PM.
    The world is waiting. I must leave you now.

  4. #4
    ATH0 quzah's Avatar
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    Originally posted by Shadow

    > it tries to open a file which doesn't exist (I want to update it, so I used "r+");
    How do you "update" a file that doesn't exist?

    I think you could find this information in any decent tutorial by searching google.
    Well he could just use "w+" which will create the file if it doesn't exist, if I remember correctly.

    Quzah.
    Hope is the first step on the road to disappointment.

  5. #5
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    Yes, so will append. They both create something if it doesn't exist.

    Update = continue, add on
    How do you update something that doesn't exist?
    The world is waiting. I must leave you now.

  6. #6
    ATH0 quzah's Avatar
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    Originally posted by Shadow
    Yes, so will append. They both create something if it doesn't exist.

    Update = continue, add on
    How do you update something that doesn't exist?
    Well the term 'update' is not really accurate, but I can see the usefulness:

    If it doesn't exist, create the file, if it does, open it for reading and updating.

    Basicly you don't have to have two seperate functions or implementations to handle this.

    Anyway, his code doesn't really need to have anything to do with signal handling. His code is incorrect because, and this is likely why it crashes, he closes a non-existing file pointer.

    Quzah.
    Hope is the first step on the road to disappointment.

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