seg_fault I can't debug

EDIT: SOLVED PROBLEM THANKS ANYWAY


I keep getting a seg_fault .. I am certain it has to do with my setting 'processed_pixels' array to some value ..

heres the gdb debug entry

Code:

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Program received signal SIGSEGV, Segmentation fault.
0x08048cbd in set_bg_processed (png_rows=0x8051000, processed_pixels=0x1)
    at splicer.c:95
95                                      processed_pixels[i][pixel_j] = 1;

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Ive commented out some code and simplified to help me find the error but I can't quite find it.

Code:

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        char **processed_pixels = malloc(img_height * sizeof(char*));
        int i;
        for(i=0;i<img_height;++i)
                processed_pixels[i] = calloc(stride, 1);

        set_bg_processed(png_rows);

---

Code:

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void set_bg_processed(png_bytepp png_rows, char **processed_pixels)
{
        int i,j;
        for(i=0;i<img_height;++i)
        {
                for(j=0;j<stride;j+=channels)
                {
                        if( 1 ) //condition code elided, still seg_faults
                        {
                                int pixel_j = j / channels;
                                printf("debug: setting %d %d to processed ... \n ",i, pixel_j);
                                assert( pixel_j >= 0); // asserting pixel_j so it can be shown that it is positive here on the forum wihout showing 'channels' code
                                processed_pixels[i][pixel_j] = 1;
                                printf("\tdone\n");
                        }
                }
        }
}

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i am new to C :(

I think it crashes on i=0, pixel_j = 0

Thanks for helping!

If the code you've shown is at all accurate, set_bg_processed() requires two arguments, but you are only passing one when you call it.

Having a variable in a function with the same name as an argument of a function does not magically pass that variable to the function.

yes , I did not know that C would let me compile the code if such an error existed

hopefully its at least a compiler warning, I should turn those on

Quote:

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Originally Posted by rodrigorules

yes , I did not know that C would let me compile the code if such an error existed

hopefully its at least a compiler warning, I should turn those on

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C will let you compile code in a lot of similar situations that look completely unreasonable. That is the beauty of C: it's a blessing and a curse at the same time.

Rule of thumb is: never assume that the C compiler will warn you about anything that seems unreasonable, as most likely it won't.