variable assuming arbitrary large values

[zahid990170]

Hi,

I have a variable of type unsigned long in my program.

unsigned long l_load;

The program runs in a loop and assigns it the values, that keep on incrementing. Let us say, a program run that assigns certain values in sequence.

For example,

0, 56, 112, 168, 224, 240

These are all, expected numbers, and can be larger than that but within range of the variable type that is unsigned long.

But, at certain runs, the program takes the following arbitrary values for the same variable. i.e.

2147680256

I was not able to figure out what can be the source of such an error,

Any ideas, what precautions I might be missing ? or under which scenario can these problems happen ?

Thanks,

[Bayint Naung]

Can you post relevant part of code.

[zahid990170]

Hi,

Please find below the part of the code.

// a structure used in the code

typedef struct 
{
	unsigned long up;
	unsigned long down;
}LOAD;


static void update_load(
		LOAD *cpl,
		void *mesg,
		unsigned short pkt
		)
{

    unsigned char c;

    for (c=0; c<3; c++)
    {
        update_first(&(cpl[c]), &(cpl[0]), m_size_us);
    }
    update_second(&(cpl[0]), m_size_us);
}


// Where the function update_load is

static void update_first(LOAD *load_p, LOAD *p_link, unsigned long m_size_us)
{
    unsigned long start;
    start = p_link_p->up;

    load_p->down += m_size_us;
}

static void update_second(LOAD *load_p, unsigned long m_size_us)
{
    load_p->up += m_size_us;
}

I have pasted some code, Will look to the inputs.

Thanks,

[Bayint Naung]

I am not seeing any problem.
It's possible that you've trashed memory. or fail to initialize variables?
Is LOAD* dynamically allocated? does it have 3 elements...?
and use debugger?

static void update_first(LOAD *load_p, LOAD *p_link, unsigned long m_size_us)
{
    unsigned long start;
    start = p_link_p->up;     // where is p_link_p ?

    load_p->down += m_size_us;
}

[tabstop]

Not that it matters to your issue: you pass p_link in to your update_first but don't use it. Your compiler is probably giving you warnings too, but only you know whether that's the right thing.

As to the issue at hand, it all comes down to what value m_size_us is, and who knows? We don't.

[zahid990170]

Hi,

thanks for the reply, it is mistake, It is actually

 start = p_link -> up

yes, I have checked the variables are initialized. load_p and p_link is passed by reference, so we have the updated values after the function returns.

I guess, I have to debug more, and come back again ...

[zahid990170]

Hi,

Thanks every one for the replies.

I have now figured out the problem.

I missed initializing one of the variables. In essence, I was going though the "for" loop one time short. And, it was because of a "for" loop limit variable that was pre-configured, and should have been changed to account for more variables in the program.

Thanks,