"The Devil function"

I have a sentence to be read, that sentece will give me the values of X2 and Y2,
The function is called readNext(arg), but it crashes when i call it, can't find out why. (no error message on windows).

Code:

int x1,x2,y1,y2;
x1 = x2 = y1 = y2 = 0;

readNext(x2);
readNext(y2);

///End of code///

//This function receives them:

    void readNext(int *arg1) {
         *arg1 = -1;
         printf("ok");
     while(*arg1 < 0 || isdigit(c)) {
         if(isdigit(c))
          *arg1 = (*arg1 < 0) ? (int)(c-'0') : *arg1 * 10 + (int)(c-'0');
       printf("3o3 arg1 = %i\n",*arg1);
       if(c==';') break;
       c = getchar();
      }
    }

But in Windows it just crashes, and i can't test it on linux yet.
Can you find out where's the error?

Thanks!

Ok i know the error now,
its a "Segmentation fault (core dumped)" error as usual in critical moments...

Run it in a debugger.

Originally Posted by rags_to_riches

Run it in a debugger.

What's the best debugger to do it?

Originally Posted by Milhas

I have a sentence to be read, that sentece will give me the values of X2 and Y2,
The function is called readNext(arg), but it crashes when i call it, can't find out why. (no error message on windows).

Code:

int x1,x2,y1,y2;
x1 = x2 = y1 = y2 = 0;

readNext(x2);
readNext(y2);

///End of code///

//This function receives them:

    void readNext(int *arg1) {
         *arg1 = -1;
         printf("ok");
     while(*arg1 < 0 || isdigit(c)) {
         if(isdigit(c))
          *arg1 = (*arg1 < 0) ? (int)(c-'0') : *arg1 * 10 + (int)(c-'0');
       printf("3o3 arg1 = %i\n",*arg1);
       if(c==';') break;
       c = getchar();
      }
    }

But in Windows it just crashes, and i can't test it on linux yet.
Can you find out where's the error?

Thanks!

You are passing an integer to readNext(), but receiving it as a pointer to an integer.

Todd

Code:

int x1,x2,y1,y2;
...
readNext(x2);
readNext(y2);
...
    void readNext(int *arg1) {

Look at those 4 lines of code. Look at them HARD. And if you still don't see the problem, look at them HARDER!

-- edit --
Aw Todd. You ruined my fun!

Thanks,
so i'll have to make that function to return a result right? (not being void)

Originally Posted by Milhas

What's the best debugger to do it?

Totally depends on the operating system and IDE. Visual Studio is great for Windows, gdb is great for Linux, Sun Workshop is great for Solaris (or was, it's been a while)...

You'll find it hard to be a competent developer in compiled languages if you are unable to use a debugger proficiently.

Originally Posted by Milhas

Thanks,
so i'll have to make that function to return a result right? (not being void)

I don't think you're looking at those 4 lines hard enough. Look at them HARDER:

Code:

int x1,x2,y1,y2;
...
readNext(x2);
readNext(y2);
...
    void readNext(int *arg1) {

Originally Posted by arpsmack

I don't think you're looking at those 4 lines hard enough. Look at them HARDER:

Too funny! (Or, just read the other posts in this thread. duh.)

Oh right! Look at those 4 lines HARDER... and listen to Todd. Or I suppose you could just pick one of those two.

What wrong with simply using scanf? It looks like you're reimplementing the wheel!

You need to start paying attention to compiler warnings and errors. Turn the warnings up to max, as well.
You should never let implicit cast to a pointer from a non-pointer type compile.

As Elysia says, turn up the warning level, and don't run the code until it clean compiles.

It's no guarantee of success, but you certainly improve the odds in the long run.

Think about the difference between
readNext(x2);
readNext(&x2);

Yes, that solves it, &x2 instead of x2.

This tiny details still make me confusion sometimes..

Thanks