Don't understand a seg fault - c++

Question

String is my own string class and Stack is my own stack class.
I am trying to change infix to postfix with values that are separated by spaces.
The function below pretty much works but also returns a "Segmentation fault (core dumped)".
String postfix(String infix){
std::vector<String> vec;
vec = infix.split(' ');
Stack<String> tmp;
String right, left, op;
int i = 0;
while (vec[i] != ';'){
if (vec[i] == ')'){
right = tmp.pop();
op = tmp.pop();
left = tmp.pop();
tmp.push(left + ' ' + right + ' ' + op);
}else{
if (vec[i] != '(' && vec[i] != ' ')
tmp.push(vec[i]);
}
++i;
}
String postfix = tmp.pop();
return postfix;
}
I do not understand why this is. Any help would be appreciated.
#ifndef STACK_HPP
#define STACK_HPP
template <typename T>
class Node{
public:
T data;
Node<T>* next;
Node() { data().next(0); } ;
Node (const T& x) : data (x), next(0) {};
};
template <typename T>
class Stack{
public:
Stack() : tos(0){};
~Stack();
Stack(const Stack<T>&);
void swap(Stack<T>& rhs);
Stack<T>& operator= (Stack<T> rhs) { swap(rhs); return *this; };
bool isEmpty() const { return tos == 0; };
T pop();
void push(const T&);
private:
Node<T> *tos;
};
///////////////////////////////////////////////////////////////
template <typename T>
Stack<T>::~Stack(){
while(tos != 0){
Node<T> *tmp = tos;
tos = tos -> next;
delete tmp;
}
}
template <typename T>
void Stack<T>::swap(Stack<T>& rhs){
Node<T> *tmp = tos;
tos = rhs.tos;
rhs.tos = tmp;
}
template <typename T>
Stack<T>::Stack(const Stack<T>& actual){
Node<T> *tmp = actual.tos, *bottom = 0;
tos = 0;
while (tmp != 0){
if(tos == 0){
tos = new Node<T>(tmp -> data);
bottom = tos;
}else{
bottom -> next = new Node<T>(tmp -> data);
bottom = bottom -> next;
}
tmp = tmp -> next;
}
}
template<typename T>
T Stack<T>::pop(){
T result = tos -> data;
Node<T> *tmp = tos;
tos = tos -> next;
delete tmp;
return result;
}
template <typename T>
void Stack<T>::push(const T& x){
Node<T> *tmp = new Node<T> (x);
tmp -> next = tos;
tos = tmp;
}
#endif
//bruce pucci
//string
//cs23001
#include <iostream>
#include <cassert>
#include <vector>
#include <fstream>
#include "string.hpp"
///////////////////////////////string class friend functions////////////////////////
////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////I/O/////////////////////////////////////////////
std::ostream& operator<<(std::ostream& out, const String& print){//std::cout operator
int i = 0;
while (print.arr[i] > 0){
out << print.arr[i];
++i;
}
return out;
}
std::ifstream& operator>>(std::ifstream& in, String& rhs){//ifstream operator.
char tmp[stringSize];//grabs word by word (chars serperated by whitespace).
in >> tmp;
rhs = String(tmp);
return in;
}
////////////////////////////////string class public functions///////////////////////
////////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////constructors///////////////////////////////////////
String::String(){//default constructor. default size
arr = new char[stringSize];
cap = stringSize;
arr[0] = 0;
}
String::String(const char a){//char constructor. default size
arr = new char[stringSize];
cap = stringSize;
arr[0] = a;
arr[1] = 0;
}
String::String(const char a[]){//char array constructor. default size
arr = new char[stringSize];
cap = stringSize;
int i = 0;
while (a[i] > 0){
arr[i] = a[i];
++i;
}
arr[i] = 0;
}
String::String(const int initSize, const char a[]){//char array constructor. size passed as a parameter
arr = new char[initSize];
cap = initSize;
int i = 0;
while (a[i] > 0){
arr[i] = a[i];
++i;
}
arr[i] = 0;
}
String::String(int initSize){//like default constructor. size passed as parameter
arr = new char[initSize];
cap = initSize;
}
//////////////////////////////////dynamic stuff/////////////////////////////////////////////////
String::String(const String& rhs){//big three. copy constructor
arr = new char[rhs.cap];
cap = rhs.cap;
for (int i = 0; i < cap; ++i)
arr[i] = rhs.arr[i];
}
String::~String(){//big three. destuctor.
delete [] arr;
}
String& String::operator=(String rhs){//big three. assignment operator.
swap(rhs);
return *this;
}
String String::swap(String& rhs){//swap the pointers on 2 char arrays.
int tmpCap = rhs.cap;
rhs.cap = cap;
cap = tmpCap;
char* tmp = rhs.arr;
rhs.arr = arr;
arr = tmp;
return *this;
}
///////////////////////////////////functions////////////////////////////////////////////////////////////////
void String::reallocate(int a){//changes the size of a dynamic String. size passed as parameter.
String tmp;
tmp.cap = a;
tmp.arr = new char[a];//allocate space of size passed.
int i = 0;
while (arr[i] != 0){//copy elements to newly allocated tmp array
tmp.arr[i] = arr[i];
++i;
}
tmp.arr[i] = 0;
swap(tmp);//swap pointers of tmp and passed array
}
std::vector<String> String::split(char splitter) const{//splits a String into a vecotr of
std::vector<String> vecOfStrings;//Strings besed on the delimited passed
int start = 0, end = 0;//returns that vector
bool doIt = false;
for (int i = 0; i < cap; ++i){//look if the delimiter exists
if (arr[i] == ' '){
doIt = true;
break;
}
}
if (doIt){//if the delimiter exists in the string start looping
for (int i = 0; i < cap; ++i){
if (arr[i] == splitter){//when each occurance of the delimiter is found create a
end = i;//node of String in the vector with the chars since the previous node
vecOfStrings.push_back(substr(start, end - 1));
start = (end + 1);
}
if (i == (cap - 1)){//do this until the no more delimiters are found
end = i;
vecOfStrings.push_back(substr(start, end));
}
}
}
return vecOfStrings;
}
int String::length() const{//returns the length of the String before the terminating char.
int counter = 0;
while (arr[counter] != 0)
++counter;
return counter;
}
int String::capacity() const{//accessor to capacity.
return cap;
}
String String::substr(int start, int end) const{//returns a subset string of string passed.
if ((start < 0) || (end < 0))//parameters are starting and ending points of the substring
return String();
String result;
int returnIndex = start;
for (int i = start; i <= end; ++i)
result[i - start] = arr[returnIndex++];
result[end - start + 1] = 0;
return result;
}
int String::findChar(const char target) const{//returns the position of the first occurance of the char
for (int i = 0; i < length(); ++i)//being searched for. returns -1 if the char is not found.
if (arr[i] == target)
return i;
std::cout << "The char was not found." << std::endl;
return -1;
}
int String::findStr(const char target[]) const{//searches for a substring in the string. returns the
String targetString(target);//position of the first char in the substring
return findStr(targetString);//uses the String version of findStr. look there for more info.
}
int String::findStr(const String& target) const{//searches for a substring in the string. returns the
int targetLength = target.length();//position of the first char in the substring
String candidate;//candidate is the string that
int candStart = 0, candEnd = candStart + (targetLength - 1), i = 0;//will be compared to other strings
//of the same length
while (i < (stringSize - targetLength)){//go through char by char and compare candidate to
candidate = substr(candStart++, candEnd++);//strings of the same length within the full string.
if (candidate == target)//ex String = "Hello World." looking for "llo"
return i;//"Hel" == "llo" no "Hel" == "ell" no "llo == "llo" yes.
i++;//return 2.
}
std::cout << "The string was not found." << std::endl;
return -1;//if not found at all return -1
}
int String::stringToInt(){
int result = 0, intTmp;
char charTmp;
for (int i = 0; i < length(); ++i){
charTmp = arr[i];
switch (charTmp){
case '0' : intTmp = 0; break;
case '1' : intTmp = 1; break;
case '2' : intTmp = 2; break;
case '3' : intTmp = 3; break;
case '4' : intTmp = 4; break;
case '5' : intTmp = 5; break;
case '6' : intTmp = 6; break;
case '7' : intTmp = 7; break;
case '8' : intTmp = 8; break;
case '9' : intTmp = 9; break;
case '-' : intTmp = 0; break;
}
if (result > 0)
result = result * 10;
result = result + intTmp;
}
return result;
}
/////////////////////////////////////////////operators////////////////////////////////////////////////////////////////////
char String::operator[](int i) const{//subscript operator. returns char whated in char array. const version.
return arr[i];//acts as an accessor to chars
}
char& String::operator[](int i){//subscript operator. returns char whated in char array. non const version.
return arr[i];//acts as an accessor to chars
}
String String::operator+(const String& rhs) const{//concatenate
String result(arr);
int start = length(), rhsIndex = 0;
while (rhs.arr[rhsIndex] != 0){
result.arr[start] = rhs.arr[rhsIndex];
start++;
rhsIndex++;
}
result.arr[start] = 0;
return result;
}
bool String::operator==(const String& rhs) const{
if (length() != rhs.length())
return false;
for (int i = 0; i < length(); ++i)
if (arr[i] != rhs.arr[i])
return false;
return true;
}
bool String::operator!=(const String& rhs) const{
if (*this == rhs)
return false;
return true;
}
bool String::operator<(const String& rhs) const{
int i = 0;
while (arr[i] != 0 && rhs.arr[i] != 0){
if ((arr[i] - rhs.arr[i]) < 0)
return true;
else if ((arr[i] - rhs.arr[i]) > 0)
return false;
i++;
}
if (length() < rhs.length())
return true;
return false;
}
bool String::operator>(const String& rhs) const{
if (*this == rhs)
return false;
if (*this < rhs)
return false;
return true;
}
bool String::operator<=(const String& rhs) const{
if (*this == rhs)
return true;
if (*this < rhs)
return true;
return false;
}
bool String::operator>=(const String& rhs) const{
if (*this == rhs)
return true;
if (*this < rhs)
return false;
return true;
}
//////////////////////////////free functions////////////////////////////////
////////////////////////////////////////////////////////////////////////////
///////////////they use the public functions of the String class////////////
String operator+(const char lhs[], const String& rhs){
String lhsString(lhs);
String result = lhsString + rhs;
return result;
}
String operator+(const char lhs, const String& rhs){
String lhsString(lhs);
String result = lhsString + rhs;
return result;
}
bool operator==(const char lhs[], const String& rhs){
String lhsString(lhs);
return lhsString == rhs;
}
bool operator==(const char lhs, const String& rhs){
String lhsString(lhs);
return lhsString == rhs;
}
bool operator!=(const char lhs[], const String& rhs){
String lhsString(lhs);
return lhsString != rhs;
}
bool operator!=(const char lhs, const String& rhs){
String lhsString(lhs);
return lhsString != rhs;
}
bool operator<(const char lhs[], const String& rhs){
String lhsString(lhs);
return lhsString < rhs;
}
bool operator<(const char lhs, const String& rhs){
String lhsString(lhs);
return lhsString < rhs;
}
bool operator>(const char lhs[], const String& rhs){
String lhsString(lhs);
return lhsString > rhs;
}
bool operator>(const char lhs, const String& rhs){
String lhsString(lhs);
return lhsString > rhs;
}
bool operator<=(const char lhs[], const String& rhs){
String lhsString(lhs);
return lhsString <= rhs;
}
bool operator<=(const char lhs, const String& rhs){
String lhsString(lhs);
return lhsString <= rhs;
}
bool operator>=(const char lhs[], const String& rhs){
String lhsString(lhs);
return lhsString >= rhs;
}
bool operator>=(const char lhs, const String& rhs){
String lhsString(lhs);
return lhsString >= rhs;
}
I've added some to the code for debugging purposes. The 6 never appears.
String postfix(String infix){
std::vector<String> vec;
vec = infix.split(' ');
Stack<String> tmp;
String right, left, op;
int i = 0;
while (vec[i] != ';'){
std::cout << 1 << std::endl;
if (vec[i] == ')'){
right = tmp.pop();
op = tmp.pop();
left = tmp.pop();
std::cout << 2 << std::endl;
tmp.push(left + ' ' + right + ' ' + op);
std::cout << 3 << std::endl;
}else{
if (vec[i] != '(' && vec[i] != ' ')
std::cout << 4 << std::endl;
tmp.push(vec[i]);
std::cout << 5 << std::endl;
}
++i;
}
std::cout << 6 << std::endl;
String postfix = tmp.pop();
return postfix;
}
Output is
-bash-4.1$ make tests
g++ -g -Wall -W -Wunused -Wuninitialized -Wshadow -iquote . -iquote ../string -c test_data3.cpp
g++ -g -Wall -W -Wunused -Wuninitialized -Wshadow string.o test_data3.o -o test_data3
./test_intStack
Everything looks good. Done testing an int Stack.
./test_stringStack
Everything looks good. Done testing a String Stack.
./test_data3
( AX + ( B * C ) ) ;
1
5
1
4
5
1
4
5
1
5
1
4
5
1
4
5
1
4
5
1
2
3
1
2
3
1
4
5
make: * [tests] Segmentation fault (core dumped)
rm test_data3.o

Answer 1

You almost certainly want to start by isolating the problem.
To do that, I'd start by doing a bit of rewriting to use your own code for the postfix conversion itself, but use std::string and std::stack for the string and stack type respectively.
If that makes the problem disappear, switch one (but not both) back to use your class. If it still works, switch the other to use your class.
Chances are very good that this will fairly quickly tell you whether the problem is in your postfix-conversion, your Stack, or your String. Once you've figured that out, I'd probably work at writing some decent unit tests for the component in question.
You could just debug it in context instead, but chances are pretty fair (at least in my experience) that doing so will often leave a number of similar problems, so the next time you try to use it, you'll run into similar problems under slightly different circumstances. By working at it more systematically you can eliminate entire classes of bugs instead of removing them one at a time.