writing custom string class in c++

I am trying to write a basic string class for practice, and I am struggling with the reserve() function to increase my char array's memory allocation.

This is the error message I get:

free(): double free detected in tcache 2

This is my approach:

void string::reserve(size_t n) { if (n <= space+1) return; // never decrease allocation char *p = new char[n+1]; // allocate new space for (int i=0; i<sz; ++i) p[i]=pChars[i]; // copy old elements //strcpy(p, pChars); // didn't work either p[n] = '\0'; delete[] pChars; // deallocate old space pChars = p; space = n+1; } 

I will also share a picture of my header file below:

Here is the entire code:

#include "String.h" namespace String { string::string(): sz(0), pChars(nullptr), space(0) {} string::string(const char* s): sz(strlen(s)), pChars(new char[strlen(s)+1]), space(sz+1) ///Constructor using a null-terminated C String { //for (int i = 0; s[i] != '\0'; i++) pChars[i] = s[i]; strcpy(pChars,s); pChars[strlen(s)] = '\0'; } string::string(const string& s): sz(s.sz), pChars(new char[s.sz]), space(s.sz) ///copy constructor { for (size_t i = 0 ; i<s.sz; i++) pChars[i] = s.pChars[i]; pChars[s.sz] = '\0'; } string& string::operator=(const string& s) ///copy assignment { if (this==&s) return *this; // self-assignment, no work needed if (s.sz<=space) { // enough space, no need for new allocation for (size_t i = 0; i<s.sz; ++i) pChars[i] = s.pChars[i]; // copy elements sz = s.sz; return *this; } char *p = new char [s.sz]; // copy and swap for (size_t i = 0; i<s.sz; ++i) p[i] = s.pChars[i]; delete[] pChars; sz = s.sz; space = s.sz; pChars = p; return *this; } string& string:: operator=(const char* s) ///copy assignment using a null-terminated C String { char *p = new char[strlen(s)+1]; for(size_t i = 0; s[i] != '\0'; i++) p[i] = s[i]; p[sz] = '\0'; delete [] pChars; sz = strlen(s); space = sz; strcpy(pChars, p); return *this; } ///string(string&& s); ///move constructor, not needed (compiler copy elision) string& string:: operator=(string&& s) ///move assignment { delete[] pChars; // deallocate old space pChars = s.pChars; // copy a's elem and sz sz = s.sz; space = s.space; s.pChars = nullptr; // make a the empty vector s.sz = 0; cout << "Move" << endl; return *this; } string::~string() { delete [] pChars; } char& string:: operator[](size_t pos) {return pChars[pos];} ///set operator const char& string:: operator[](size_t pos) const {return pChars[pos];} ///get operator void string::reserve(size_t n) { if (n <= space+1) return; // never decrease allocation char *p = new char[n+1]; // allocate new space for (int i=0; i<sz; ++i) p[i]=pChars[i]; // copy old elements //strcpy(p, pChars); p[sz] = '\0'; delete[] pChars; // deallocate old space pChars = p; space = n+1; } void string:: push_back(const char c) ///push char c to the end { if (sz==0) // no space: grab some reserve(8); else if (sz==space) // no more free space: get more space reserve(2*space); pChars[sz] = c; // add d at end ++sz; // and increase the size (sz is the number of elements) } bool operator==(const string& lhs, const string& rhs) ///check equality (same size, all chars the same) { if (lhs.size() != rhs.size()) return false; else { for (size_t i = 0; i<lhs.size(); i++) { if (lhs[i] != rhs[i]) return false; } } return true; } bool operator==(const string& lhs, const char* rhs) ///equality with null terminated C string { if(lhs.size() == strlen(rhs)) { for (size_t i = 0; i< lhs.size(); i++) { if(lhs[i] == rhs[i]) return true; } } return false; } bool operator>(const string& lhs, const string& rhs) ///greater than operator, true if lhs > rhs { } string operator+(const string& lhs, const string& rhs) ///concatenate two MyStrings, return the result { } ostream& operator<<(ostream& os, const string& s) { for (size_t i = 0; i<s.size(); i++) { os << s[i]; } return os; } istream& operator>>(istream& is, string& s) { char c; while(is.get(c)) { if (c!=' ') s.push_back(c); } return is; } }