Greetings Gcc Folks,
Either this is me doing something very simple in a school assignment for
creating a basic hashtable
or a compiler bug. I am currently seeing this error during my tables run on
copy constructor call during
the tester and have set to find out why it doesn't work. After some googling it
seems either I am doing
string pointer to string swaps.
or it's a compiler bug. This is the error I am getting after running in gdb
with backtrace:
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7b769bb in std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> >::basic_string(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > const&) ()
from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
(gdb) backtrace
#0 0x00007ffff7b769bb in std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char>
>::basic_string(std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> > const&) ()
from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#1 0x00000000004067f6 in HashTable<int>::Record::getKey() const ()
#2 0x00000000004060ee in HashTable<int>::HashTable(HashTable<int> const&) ()
#3 0x0000000000403cab in main ()
This is the complete code for the project:
#include <string>
#include <utility>
#include<iostream>
using namespace std;
/*The functions I updated for Simple Table are
1.search
2.grow
3.update
4.Both Copy Constructor and Copy Assignment
5.Destructor
*/
template <class TYPE>
class Table {
public:
Table() {}
virtual bool update(const string& key, const TYPE& value) = 0;
virtual bool remove(const string& key) = 0;
virtual bool find(const string& key, TYPE& value) = 0;
virtual ~Table() {}
};
template <class TYPE>
class SimpleTable :public Table<TYPE> {
struct Record {
TYPE data_;
string key_;
Record(const string& key, const TYPE& data) {
key_ = key;
data_ = data;
}
};
Record** records_; //the table
int max_; //capacity of the array
int size_; //current number of records held
int search(const string& key);
void sort();
void grow();
public:
SimpleTable(int maxExpected);
SimpleTable(const SimpleTable& other);
SimpleTable(SimpleTable&& other);
virtual int numRecords();
virtual bool isEmpty();
virtual bool update(const string& key, const TYPE& value);
virtual bool remove(const string& key);
virtual bool find(const string& key, TYPE& value);
virtual const SimpleTable& operator=(const SimpleTable& other);
virtual const SimpleTable& operator=(SimpleTable&& other);
virtual ~SimpleTable();
};
//returns index of where key is found.
template <class TYPE>
int SimpleTable<TYPE>::search(const string& key) {
int rc = -1;
for (int i = 0; i<size_; i++) {
if (records_[i]->key_ == key) {
rc = i;
break;
}
}
return rc;
}
//checks if array is empty
template <class TYPE>
bool SimpleTable<TYPE>::isEmpty(){
return size_==0;
}
template <class TYPE>
//return size of array
int SimpleTable<TYPE>::numRecords(){
return size_;
}
//sort the according to key in table
template <class TYPE>
void SimpleTable<TYPE>::sort() {
int minIdx = 0;
for (int i = 0; i<size_; i++) {
minIdx = i;
for (int j = i + 1; j<size_; j++) {
if (records_[j]->key_ < records_[minIdx]->key_) {
minIdx = j;
}
}
Record* tmp = records_[i];
records_[i] = records_[minIdx];
records_[minIdx] = tmp;
}
}
//grow the array by one element
template <class TYPE>
void SimpleTable<TYPE>::grow() {
Record** newArray = new Record*[max_ + 1];
max_ = max_ + 1;
for (int i = 0; i<size_; i++) {
newArray[i] = records_[i];
}
records_ = std::move(newArray);
}
/* none of the code in the function definitions below are correct. You can
replace what you need
*/
template <class TYPE>
SimpleTable<TYPE>::SimpleTable(int maxExpected) : Table<TYPE>() {
records_ = new Record*[maxExpected];
max_ = maxExpected;
size_ = 0;
}
template <class TYPE>
SimpleTable<TYPE>::SimpleTable(const SimpleTable<TYPE>& other) {
records_ = new Record*[other.max_];
max_ = other.max_;
size_ = 0;
for (int i = 0; i<other.size_; i++) {
update(other.records_[i]->key_, other.records_[i]->data_);
}
}
template <class TYPE>
SimpleTable<TYPE>::SimpleTable(SimpleTable<TYPE>&& other) {
size_ = swap(other.size_);
max_ = swap(other.max_);
records_ = swap(other.records_);
}
template <class TYPE>
bool SimpleTable<TYPE>::update(const string& key, const TYPE& value) {
int idx = search(key);
if (idx == -1) {
if (size_ == max_) {
grow();
}
records_[size_++] = new Record(key, value);
for(int i=0;i<size_;i++) {
if(records_[i]->key_ > records_[size_-1]->key_) {
Record* tmp = records_[i];
records_[i] = records_[size_-1];
records_[i] = tmp;
}
}
}
else {
records_[idx]->data_ = value;
}
return true;
}
template <class TYPE>
bool SimpleTable<TYPE>::remove(const string& key) {
int idx;
idx=search(key);
if(idx!=-1){
delete records_[idx];
for(int i=idx;i<size_-1;i++){
records_[i]=records_[i+1];
}
size_--;
return true;
} else {
return false;
}
}
template <class TYPE>
bool SimpleTable<TYPE>::find(const string& key, TYPE& value) {
int idx = search(key);
if (idx == -1) {
return false;
} else {
value = records_[idx]->data_;
return true;
}
}
template <class TYPE>
const SimpleTable<TYPE>& SimpleTable<TYPE>::operator=(const SimpleTable<TYPE>&
other) {
if (this != &other) {
if(records_){
delete[] records_;
}
records_ = new Record*[other.max_];
max_ = other.max_;
size_ = 0;
for (int i = 0; i<other.size_; i++) {
update(other.records_[i]->key_,
other.records_[i]->data_);
}
}
return *this;
}
template <class TYPE>
const SimpleTable<TYPE>& SimpleTable<TYPE>::operator=(SimpleTable<TYPE>&&
other) {
swap(records_, other.records_);
swap(size_, other.size_);
swap(max_, other.max_);
return *this;
}
template <class TYPE>
SimpleTable<TYPE>::~SimpleTable() {
if (records_) {
int sz=size_;
for(int i=0;i<sz;i++){
remove(records_[0]->key_);
}
}
}
template <class TYPE>
class HashTable :public Table<TYPE> {
// This is the internal structure for array elements for hastable
struct Record {
TYPE data_; // data per array element
string key_;//key to lookup for data element
Record* next_; // next record to create linkly linked
list for bucketing
// Constructor to set values of Record
Record(const string key, const TYPE data) {
key_ = key;
data_ = data;
next_=nullptr;
}
//empty Constructor that sets values to empty safe state
Record(){
key_="";
data_=0;
next_=nullptr;
}
//Returns key of Record
string getKey() const {
return key_;
}
//Sets key of Record
string setKey(string key) {
key_=key;
}
//Returns data member of Record
TYPE getData() const {
return data_;
}
//Sets data member of Record
void setData(TYPE data) {
data_=data;
}
//Gets next element in linked list for bucketing
Record *getNext() const {
return next_;
}
//Sets next element in linked list for bucketing
void setNext(Record *next) {
next_ = next;
}
};
Record** table_; //the table
int size_;//size_
int cap;//max number of records allowed in table
std::hash<std::string> hash;//hash function used
public:
HashTable(int maxExpected);
HashTable(const HashTable& other);
HashTable(HashTable&& other);
int numRecords();
bool isEmpty();
virtual bool update(const string& key, const TYPE& value);
virtual bool remove(const string& key);
virtual bool find(const string& key, TYPE& value);
virtual const HashTable& operator=(const HashTable& other);
virtual const HashTable& operator=(HashTable&& other);
virtual ~HashTable();
};
/* none of the code in the function definitions below are correct. You can
replace what you need
*/
//returns size of table
template <class TYPE>
int HashTable<TYPE>::numRecords() {
return size_;
}
//returns if hashtable has no records been inserted
template <class TYPE>
bool HashTable<TYPE>::isEmpty(){
return size_==0;
}
//Constructor that allocates memory equal to passed amount in maxExpected and
sets hashtable to empty state
template <class TYPE>
HashTable<TYPE>::HashTable(int maxExpected) : Table<TYPE>() {
int size_=0;
table_=new Record*[maxExpected]();
cap=maxExpected;
}
//Copy Constructor that creates a copy of passed hashtable as argument to
create a new copy of including memory allocations
template <class TYPE>
HashTable<TYPE>::HashTable(const HashTable<TYPE>& other) {
table_ = new Record*[other.cap];
size_=other.size_;
hash = other.hash;
cap=other.cap;
for(int i=0;i<cap;i++){
if(other.table_==nullptr){
continue;
}
string key=other.table_[i]->getKey();
table_[i]->key_=key;
TYPE data=other.table_[i]->getData();
table_[i]->setData(data);
}
}
//Move constructor that moves the hashtable passed into the current table being
constructed
template <class TYPE>
HashTable<TYPE>::HashTable(HashTable<TYPE>&& other) {
swap(size_,other.size_);
swap(cap,other.cap);
swap(table_,other.records_);
swap(hash,other.hash);
}
//Updates record with the string passed to the new data for the record's data
element and returns true if found/updated otherwise false
template <class TYPE>
bool HashTable<TYPE>::update(const string& key, const TYPE& value) {
int hashvalue=hash(key)%cap;
Record* prev=nullptr;
Record* entry=table_[hashvalue];
while (entry != nullptr && entry->getKey() != key) {
prev=entry;
entry=entry->getNext();
}
if (entry == nullptr) {
entry = new Record(key, value);
if (prev == nullptr) {
// insert as first bucket
table_[hashvalue] = entry;
} else {
prev->setNext(entry);
}
} else {
// just update the value
entry->setData(value);
}
size_++;
return true;
}
//Removes the record with the string passed for the key value and returns true
if removed otherwise false if not found
template <class TYPE>
bool HashTable<TYPE>::remove(const string& key) {
int hashValue = hash(key)%cap;
Record *prev = nullptr;
Record *entry = table_[hashValue];
while (entry != nullptr && entry->getKey() != key) {
prev = entry;
entry = entry->getNext();
}
if (entry == nullptr) {
// key not found
return false;
}
else {
if (prev == nullptr) {
// remove first bucket of the list
table_[hashValue] = entry->getNext();
} else {
prev->setNext(entry->getNext());
}
delete entry;
}
size_--;
return true;
}
//Finds value in table and updates with the value passed if found returns true
otherwise false
template <class TYPE>
bool HashTable<TYPE>::find(const string& key, TYPE& value) {
int hashValue = hash(key)%cap;
Record* entry =table_[hashValue];
while (entry != nullptr) {
if (entry->getKey() == key) {
value=entry->getData();
return true;
}
entry = entry->getNext();
}
return false;
}
//Copy Assignment Operator creates copy of hashtable passed into current
hashtable
template <class TYPE>
const HashTable<TYPE>&HashTable<TYPE>::operator=(const HashTable<TYPE>& other) {
if (table_) {
delete[] table_;
}
table_ = new Record*[other.cap];
size_=other.size_;
hash = other.hash;
cap=other.cap;
for(int i=0;i<cap;i++){
if(other.table_==nullptr){
continue;
}
string key=other.table_[i]->getKey();
table_[i]->key_=key;
TYPE data=other.table_[i]->getData();
table_[i]->setData(data);
}
return *this;
;
}
//Moves Assignment Operator which moves passed hashtable into current hashtable
template <class TYPE>
const HashTable<TYPE>& HashTable<TYPE>::operator=(HashTable<TYPE>&& other) {
swap(size_,other.size_);
swap(table_,other.table_);
swap(hash,other.hash);
swap(cap,other.cap);
return *this;
}
//Destructor this destroys the hashtable when it goes out of scope or is called
directly
template <class TYPE>
HashTable<TYPE>::~HashTable() {
// destroy all buckets one by one
for (int i = 0; i < cap; ++i) {
Record *entry = table_[i];
while (entry != nullptr) {
Record *prev = entry;
entry = entry->getNext();
delete prev;
}
table_[i] = nullptr;
}
// destroy the hash table
delete [] table_;
}
G++ Version/Toolchain used as with gcc -v:
Using built-in specs.
COLLECT_GCC=/usr/bin/g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
5.4.0-6ubuntu1~16.04.4' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs
--enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-5 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib
--disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib
--with-tune=generic --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4)
Huge Thanks for any help,
Nick
