Re: C++ std::string tries to free() a not allocated pointer ?
Re: C++ std::string tries to free() a not allocated pointer ?
- Subject: Re: C++ std::string tries to free() a not allocated pointer ?
- From: Jean-Denis Muys <email@hidden>
- Date: Thu, 19 Nov 2009 16:46:40 +0100
On Thursday, November 19, 2009, at 04:26PM, "Paul Sanders" <email@hidden> wrote:
>What does your destructor do? Your copy constructors / assignment operators
>appear to copy the pointer, rather than making a copy of the data pointed
>to, so perhaps you end up freeing the pointer twice (once for each SQLString
>object destroyed).
>
>Paul Sanders.
The destructor is so simple:
~SQLString() {}
But the constructors do not copy pointers, as the data member is not a pointer, but a full blown std::string.
At this point, let me post the full class (I snipped the namespace stuff). Overall, not much has been left out anyway :-)
class SQLString
{
std::string realStr;
public:
static const size_t npos = std::string::npos;
~SQLString() {}
SQLString() {}
SQLString(const SQLString & other) : realStr(other.realStr) {}
SQLString(const std::string & other) : realStr(other) {}
SQLString(const char other[]) : realStr(other) {}
SQLString(const char * s, size_t n) : realStr(s, n) {
// jdmuys debug malloc error 2009-11-18
std::cerr << "making SQLString from char* " << (void*)s << " of length " << n << std::endl;
}
// Needed for stuff like SQLString str= "char * string constant"
const SQLString & operator=(const char * s)
{
realStr = s;
return *this;
}
const SQLString & operator=(const std::string & rhs)
{
realStr = rhs;
return *this;
}
const SQLString & operator=(const SQLString & rhs)
{
realStr = rhs.realStr;
return *this;
}
// Conversion to st::string. Comes in play for stuff like std::string str= SQLString_var;
operator const std::string &() const
{
return realStr;
}
/** For access std::string methods. Not sure we need it. Makes it look like some smart ptr.
possibly operator* - will look even more like smart ptr */
std::string * operator ->()
{
return & realStr;
}
int compare(const SQLString& str) const
{
return realStr.compare(str.realStr);
}
int compare(const char * s) const
{
return realStr.compare(s);
}
int compare(size_t pos1, size_t n1, const char * s) const
{
return realStr.compare(pos1, n1, s);
}
const std::string & asStdString() const
{
return realStr;
}
const char * c_str() const
{
return realStr.c_str();
}
size_t length() const
{
return realStr.length();
}
SQLString & append(const std::string & str)
{
realStr.append(str);
return *this;
}
SQLString & append(const char * s)
{
realStr.append(s);
return *this;
}
const char& operator[](size_t pos) const
{
return realStr[pos];
}
size_t find(char c, size_t pos = 0) const
{
return realStr.find(c, pos);
}
size_t find(const SQLString & s, size_t pos = 0) const
{
return realStr.find(s.realStr, pos);
}
SQLString substr(size_t pos = 0, size_t n = npos) const
{
return realStr.substr(pos, n);
}
const SQLString& replace(size_t pos1, size_t n1, const SQLString & s)
{
realStr.replace(pos1, n1, s.realStr);
return *this;
}
size_t find_first_of(char c, size_t pos = 0) const
{
return realStr.find_first_of(c, pos);
}
size_t find_last_of(char c, size_t pos = npos) const
{
return realStr.find_last_of(c, pos);
}
const SQLString & operator+=(const SQLString & op2)
{
realStr += op2.realStr;
return *this;
}
};
/*
Operators that can and have to be not a member.
*/
inline const SQLString operator+(const SQLString & op1, const SQLString & op2)
{
return sql::SQLString(op1.asStdString() + op2.asStdString());
}
inline bool operator ==(const SQLString & op1, const SQLString & op2)
{
return (op1.asStdString() == op2.asStdString());
}
inline bool operator !=(const SQLString & op1, const SQLString & op2)
{
return (op1.asStdString() != op2.asStdString());
}
inline bool operator <(const SQLString & op1, const SQLString & op2)
{
return op1.asStdString() < op2.asStdString();
}
// operator << for SQLString output
inline ostream & operator << (ostream & os, const sql::SQLString & str )
{
return os << str.asStdString();
}
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