Thread: very simple

hi all...

just getting into c. trying to understand pointers. reading the C programming language book. i have a few very simple lines of code that produce:

Bus error (core dumped)

here is the code:

Code:

int main () {
        int k, *p, *m,l;
        k = 10;
        p = &k;
        *p = 23;  //   line 5 
         l = *p;
         *m = l;  // problem line
     
        printf("%d\n",*m);

        return 0;
}

the cc -Wall doesnt complain. but if i run it i get the above bus error.
if i coment out the 'problem line' it works fine. don't understand since 'line 5' is pretty much the same statement except instead of actually assigning a number i assign the 'l' variable that holds that number.
i know that if i change 'problem line' to m = &l; it works fine. i just dont understand why it wouldn't work the other way around. like in line 5.

is it because *m doesnt even have an address yet?

i'd appreciate an explanation. thanks....

Originally Posted by toshog

the cc -Wall doesnt complain.

That is interesting. I would expect that the compiler can see that m is being used while not initialized.

I just verified: gcc 3.4.3 indeed doesn't complain, Visual Studio 2005 gives a warning: "uninitialized local variable 'm' used".

Does anyone have a gcc 4 version around to test this? I'd be interested to know whether that one warns about this.

--
Computer Programming: An Introduction for the Scientifically Inclined

Which address "m" should get?