Anyone help me with segmentation fault

I am having trouble with my decoder and was wondering if anyone could help me out?

basically, i am trying to build a decoder for my steganography encoder, the encoder places a bit from a message on the LSB of every Byte from in the sound file

the Decoder job is to collect those bits up and create a new message out of them

the code is meant to do the following:

CODE: SELECT ALL

Go to message array location.

set bitindex to 0 an increment till 7 // (8 bits to a byte)

go to sound array location

if soundbit is equal add 0 to new byte otherwise add one to end of new byte

perform bitshift left once

increment bitindex

by using various printf's I can tell you it runs smoothly about 3/4 times before crashing.

Hope that makes sense the actual loops look like this:

 {


int mIndex, sIndex, bitIndex, mask;
char *message[9];

mask = 1;
mIndex = 0;


unsigned char *soundFile = LoadWavAudioFile("boomedit.wav");

int soundFileSize = GetSizeOfWavFile();



bitIndex = 0;

    for(mIndex = 0; mIndex < 8; mIndex++)//index for message
    {
        printf("1\n");
        for(sIndex = 0; sIndex < soundFileSize; sIndex++)//index for soundfile
        {
            printf("2\n");
            for(bitIndex = 0; bitIndex < 8;)
            {
                printf("3\n");
                int test;
                if((soundFile[sIndex] & mask) > 0)//is message bit > 0
                {                                   
                    printf("++++++++++++++++\n");
                    *message[mIndex] = (soundFile[sIndex] | 1);//adds a one to message byte
                    *message[mIndex] = *message[mIndex] <<1;    //shift bits 1 placce left
                    printf("*****************\n");

                }
                else
                { //no change the LSB to 0
                    printf("------------------\n");
                    *message[mIndex]= soundFile[sIndex] & 254; //adds a zero at end o
                    *message[mIndex] = *message[mIndex] <<1; //shifts bits 1 place to left
                    printf("******************\n");
                }

                bitIndex++;
            }   
        }
    }

printf("\n hiddden letters:%s\n", *message); //print message    
printf("\nalert 5\n");

}

Hope that helps anything will be helpfull.

Solution

The problem is here:

char *message[9];

You've made an array of 9 pointers to characters, you don't assign them any value or allocate them any memory. They're uninitialized.

The first thing you do now is deference one of those uninitialized pointers:

*message[mIndex] =

Thus you crash.

Edit:

You can initialize it to all NULLs via:

char *message[9] = {0};

But you still can't use that, not it will just seg fault on deferencing a NULL pointer. You have to assign some memory to these to be useful.. for example you could do:

message[0] = malloc(100); // I don't know how much you need for your strings
message[1] = malloc(100); // that's up to you, so I'm just arbitrally picking 100 bytes
message[2] = malloc(100); // here to illustrate the point.
message[3] = malloc(100);
message[4] = malloc(100);
message[5] = malloc(100);
message[6] = malloc(100);
message[7] = malloc(100);
message[8] = malloc(100);

Then you'll have to free each of them when you're done. Is this want you wanted? An array of strings?

This line:

printf("\n hiddden letters:%s\n", *message); //print message

implies to me that you were really after just a single string...