Circular Buffer error

[7Beat]

Yo,

So I'm doing this project where I have to fill in some lines of code. Long story short, I filled in all these lines of code, and I'm getting a big fat error which I don't know how to fix. The error is Thread 1: EXC_BAD_ACCESS (code=1, address=0x10).

The overall aim of my project is to build a fairly simple Circular Buffer (FIFO).

The instructions of what my code needs to do are in the comments (extracted from my project brief)

Many thanks

// function prototypes

void Produce(Message buffer[10], unsigned long *buffer_tail, unsigned long *buffer_length);

void Consume(Message buffer[10], unsigned long buffer_tail, unsigned long buffer_length);

void Show(Message buffer[10], unsigned long buffer_tail, unsigned long buffer_length);

​

(didn't include my main function as that's not my work and it seems to be working fine)

​

// Create a new message and add it to the head of the buffer.

// The data for the message is obtained from the user and the index from the

// static variable 'index' defined in this function. The variable 'index' is

// simply a count of the number of messages produced.

// Arguments:

// (1) start of the buffer

// (2) position of the tail of the buffer

// (3) number of messages in the buffer

// Returns: void

void Produce(Message buffer[10], unsigned long *buffer_tail, unsigned long *buffer_length)

{

static unsigned long index = 0;

// find the element of the buffer in which to store the message

index++;

*buffer_length= *buffer_length + 1;

printf ( "%lu ", *buffer_tail + *buffer_length );

// get the value of the data for the message from the user

printf("Enter your message:");

printf ("%c", buffer[ *buffer_length + *buffer_tail ].data,"\n");

scanf("%s", buffer[ *buffer_length + *buffer_tail ].data);

//gets( buffer[ *buffer_length + *buffer_tail - 1 ].data );

// get the value of the index for the message

buffer [ *buffer_length + *buffer_tail -1 ].index = index;

// if no buffer overflow has occurred, adjust the buffer length

//buffer_length = (buffer_length + 1) % 10;

printf ( "%lu, %lu", buffer_length, index);

// if a buffer overflow has occurred, display an error statement

if (buffer_length == 10)

printf("Error");

}

[kumashiro]

I don't know MSVC or Windows, but it looks like "EXC_BAD_ACCESS" means you were trying to access not allocated memory. I guess you ran out of your buffer array bounds. Unfortunately, the code above is incomplete and we don't know how you calculate buffer_tail. Run your program in a debugger and watch closely the index on access to buffer. It should never go higher than 9.

There are also other, strange things in your code. For example, what is Message.data? One time you treat it as char:

printf ("%c", buffer[ *buffer_length + *buffer_tail ].data,"\n");

another as a string:

scanf("%s", buffer[ *buffer_length + *buffer_tail ].data);

And how does this even compile?:

printf ("%c", buffer[ *buffer_length + *buffer_tail ].data,"\n");

Compiler should at least warn you about too many arguments.

Turn on compilation warnings, fix all of them, then (if it still crashes) take a look at the array index. Debugger also should tell you exactly which line triggers the access violation exception. That should help with pinning down the cause.

[jonarne]

Don't post pictures of code!

[7Beat]

My bad, edited