access violation in int array

This is a discussion on access violation in int array within the C Programming forums, part of the General Programming Boards category; Hello everyone, There is error message when executing my program, Unhandled exception at 0x00411a49 in test_entern.exe: 0xC0000005: Access violation reading ...

  1. #1
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    access violation in int array

    Hello everyone,


    There is error message when executing my program,

    Unhandled exception at 0x00411a49 in test_entern.exe: 0xC0000005: Access violation reading location 0x00000002.

    It is very simple, does anyone know what is wrong with the program?

    I have tested that when changing from extern int* p_int to extern int p_int[16], my program is ok. But I think the two statements should be the same, right?

    foo.c

    Code:
    int p_int [16] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17};
    goo.c

    Code:
    extern int* p_int;
    
    int main (int argc, char** argv)
    {
            int i;
            int sum = 0;
            for (i = 0; i < 16; i++)
            {
                    sum += p_int [i]; // access violation
            }
    
            return 0;
    }

    thanks in advance,
    George

  2. #2
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    Quote Originally Posted by George2 View Post
    I have tested that when changing from extern int* p_int to extern int p_int[16], my program is ok. But I think the two statements should be the same, right?
    In foo.c, you could even use
    Code:
    extern int p_int[];
    A pointer is not the same as an array although you can use array notation for dereferencing a pointer. (In other words, deferenced pointer notation and array notation are interchangeable in source code.)

    However...

    When the linker tries to match up symbols in the symbol table from one object file to symbols in the other, the data types must be the same, otherwise: bloooey.

    D.

  3. #3
    and the hat of wrongness Salem's Avatar
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    Dave's answer is correct.

    > Unhandled exception at 0x00411a49 in test_entern.exe: 0xC0000005: Access violation reading location 0x00000002.
    If you want more fun, change the first element of the array and observe the change in the attempted memory access address.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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