question about a struct pointer parameter

**vanalex** · June 8th, 2009, 02:49 PM

Hello everybody!
Recently while i was experimenting with some code written in c++ i noticed something that confused me a bit. In that code i had to deal with 2 structs :

Code:

struct date
{
    string day;
    int month; 
    int dday;
   int year; };

and the other struct

Code:

struct note
{
     date d;
     string notice;  };

I noticed that when i was passing in a function i built, an instance of note struct as a pointer parameter my program kept crashing continuously, although compiler wasn't complaining. To make myself clear :

Code:

void myFunction(note* n, ...other parameters...)
{
    cout << n->d.day << endl;
   cout << n->d.month << endl;
    etc...
}

I'm sure that my program crashed because of that piece of code

Code:

n->d.day

i'm sure because i tested it in debug mode.
When i wrote my function differently i had no problem running my program :

Code:

 void myFunction(note& n, ..other parameters...)
{
    cout << n.d.day << endl;
    cout << n.d.month << endl;
  etc...
  }

Has anyone got an idea why the pointer parameter and the arrow
caused that problem? Looking forward to reading your ideas and thoughts...Thank you in advance for your time...

vanalex

**Lindley** · June 8th, 2009, 03:01 PM

I doubt that could be the cause.

Most likely that std::string is getting corrupted somehow, though. Make sure you aren't trying to use memset, memcpy, or anything like that.

**vanalex** · June 8th, 2009, 03:37 PM

Thank you very much for your reply Lindley, but i found what caused the whole problem. The . operator precedes the -> operator in expressions so i had to write my code like this:

Code:

(n->).d.day

wrong way without parenthesis:

Code:

n->d.day

vanalex

**vanalex** · June 8th, 2009, 03:39 PM

No wrong again!

RIGHT CODE

Code:

(n->d).day

sorry...

**rohshall** · June 9th, 2009, 12:34 AM

Originally Posted by vanalex

No wrong again!

RIGHT CODE

Code:

(n->d).day

sorry...

I don't think that is the reason. -> and . operators have the same preference and they have left to right associativity.
http://cppreference.com/wiki/operator_precedence