Passing a list pointer to a function

[thilangane]

Hi,

I am working on a project and when I run my code, I get a segfault. I checked it with valgrind, and it says that I am trying to access a memory location that I maybe not malloc'd, stack'd or recently free'd. The only 'mysterious' thing I'm doing is, passing the pointer of a structure list to a function. Here is the code I get the segfault.

int GetFieldInt(list<fieldInfo> *listIn)
{
  list<fieldInfo>::iterator tempItr;
  int listCount = 0;

  tempItr = (*listIn).begin();
  while(tempItr != (*listIn).end())
    {
      listCount++;
      (*tempItr).percentage = ((*tempItr).percentage)*targetCount/100; //segfault here
      tempItr++;
    }
  if(listCount == 0)
    {
      cout<<"Field not defined!\n";
      return -1;
    }
  else
    return (int)MAX_RAND/listCount;
}

It's a rather long code. Whenever I pass the list pointer to a function, funny things happen. Sometimes, in the linux terminal, the font changes to some weird symbols. Can anyone help me with this?

Your help is much appreciated. Thanks in advance.

Thilan

[thelamb]

Ok first of all: Why are you passing this list as pointer and not a const&? You are not modifying the passed list in any way...
If you insist on using a pointer to pass it, we need to see how you're calling this function to be able to see what's wrong.

[thilangane]

Thanks for the reply. In fact, I am modifying the list in the following line:

(*tempItr).percentage = ((*tempItr).percentage)*targetCount/100; //segfault here

The list I'm passing is a global variable in main. This method is in a different file and I extern to use the list. Following is the function call:

vlanPriorityInt = GetFieldInt(&vlanPriority)

Thank you

[thilangane]

I figured it out. The lists that I am using are used iteratively. At the beginning of each iteration, they should be empty. But I forgot to clear them at the end of the iteration. So they got augmented each iteration which caused the segfault.

Now it's working fine. Thanks 'thelamb' for your reply.