good code bad answer

my code is 110% correct; eg no errors and runs properly. see.

int _val;

int myfunc2(int val)
{
  _val = val;
   return _val;
};

int Bar(int val)
{
  return _val + val + 1;
};

void myfunc1(int val)
{
  _val += Bar(val);
};

etc
etc
etc

it doesnt give me the right answer sometime.

HEEEEEEEELLLLLLLPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP