I would like to understand why I am getting a bus error with this code.
int main()
{
int p=34;
int *pp= (int *) ((char *)&p+1);
cout<<*pp<<"\n";
return 0;
}
I would like to understand why I am getting a bus error with this
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I would like to understand why I am getting a bus error with this code.
int main()
{
int p=34;
int *pp= (int *) ((char *)&p+1);
cout<<*pp<<"\n";
return 0;
}
It will no doubt be an alignment issue. On many architectures, certain types have to be aligned properly, an example being that 4-byte integers must start on a 4-byte boundary.
If you access non-aligned data, some architectures won’t care, others will run slower, still others (such as in this case) will fall in a screaming heap.
When you create the integer
p, it will be aligned correctly on the stack at an address which is a correct multiple.By moving that address up on byte, and de-referencing that as an
int, you’re causing theSIGBUS.This link at Oracle shows the alignment requirements. In short: