Problem with file and array

This is a discussion on Problem with file and array within the C Programming forums, part of the General Programming Boards category; Hi! I've a problem with my code, please help me to undestand what is going on... I open a file ...

  1. #1
    Registered User paok's Avatar
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    Problem with file and array

    Hi! I've a problem with my code, please help me to undestand what is going on...
    I open a file and I save all it's characters in an array, which I call "instruction_name". Then I close the file. Finally, I open a new file and I save all it's characters in an another array (register_name), and after this I close the file, as before. The problem is that after the open/read/close of the second file, the first two elements of the "instruction_name" array are being missed! For example let's say that the "instruction_name" array is like this: "NOPADDINC ...". After the second file the "instruction_name" array is "ασPADDINC ...". What is going on?

    My code is like this
    Code:
         FILE *readinstructions;
         printf("Loading the file which contains the instructions... ");
         if ((readinstructions=fopen("instructions.txt","r"))==NULL){
            printf("\nError: Cannot open the instructions.txt");
            }
         else printf("successful");
         
         i=0;
         while ((character=fgetc(readinstructions))!=EOF){
               instruction_name[i]=character;
               i++;
               }
         
         fclose(readinstructions);
         
    
         FILE *readregisters;
         printf("\nLoading the file which contains the registers...");
         if ((readregisters=fopen("registers.txt","r"))==NULL){
            printf("\nError: Cannot open the registers.txt");
            }
         else printf(" successful");
         
         i=0;
         while ((character=fgetc(readregisters))!=EOF){
               register_name[i]=character;
               i++;
               }
         
         fclose(readregisters);
    PS: I use DEV C++

  2. #2
    CSharpener vart's Avatar
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    1. when you failed to open file - you just print message and continue to use null pointer
    2. where is declaration of register_name, instruction_name, character?
    3. don't you need to prevent memory overrun?
    4. don't you need to nul-terminate the string read from file?
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  3. #3
    Registered User paok's Avatar
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    1. When fail happens the program is not running. In my original code, I've a "check" boolean variable which turns to FALSE when the program fails to open the file. I thought that it wasn't needed.
    2.
    Code:
     
    char instruction_name[36],register_name[24];
    int character;
    I can't understand why the elements of the array change. They are saved in the array, aren't they?

  4. #4
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    The easiest and most likely way it's happening, is that you're running outside the array boundaries, (in one or both arrays), and simply over-writing the array's contents.

    Print the first array, like this:

    Index Number===>Value
    ==================
    0. First Array element value
    1. Second array element value

    etc.

    See if your index's are what they should be, and your values are what you think they are.

    Then do the same thing with your second array. I know you'll be surprised. The wrong values, and it's index number, should give you a huge clue about what's going wrong with your program.

  5. #5
    Registered User paok's Avatar
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    I see that the address of the instruction_name starts at 2358912 and the address of the register_name ends at 2358911

  6. #6
    CSharpener vart's Avatar
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    If you write into the instruction_name more than the 36 chars - you will overwrite the register_name...
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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