CODEWITHSUNDEEP
c++exceptioncompilationg++
Elfayer
Elfayer

Reputation: 4571

C++ - Compilation error with Error class that inherit from std::exception

Here is my Error class to handle errors with try & catch :

#include <stdexcept>
#include <string>

  class Error : public std::exception
    {
    public:
      Error(const std::string&) throw();
      ~Error() throw();
      const char*   what() const throw();
    private:
      std::string           _msg;
    };

And the cpp file :

#include "Error.hpp"

Error::Error(const std::string& msg) throw()
  : _msg(msg)
{
}

Error::~Error() throw()
{
}

const char*     Error::what() const throw()
{
  return (_msg.c_str());
}

And I have this errors while compiling:

main.o:(.gcc_except_table+0x34): undefined reference to `typeinfo for Error'
MailBox.o: In function `MailBox::MailBox(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
MailBox.cpp:(.text+0x245): undefined reference to `Error::Error(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
MailBox.cpp:(.text+0x268): undefined reference to `Error::~Error()'
MailBox.cpp:(.text+0x270): undefined reference to `typeinfo for Error'
MailBox.cpp:(.text+0x2f0): undefined reference to `Error::Error(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
MailBox.cpp:(.text+0x313): undefined reference to `Error::~Error()'
MailBox.cpp:(.text+0x31b): undefined reference to `typeinfo for Error'
MailBox.cpp:(.text+0x3d6): undefined reference to `Error::Error(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
MailBox.cpp:(.text+0x3f9): undefined reference to `Error::~Error()'
MailBox.cpp:(.text+0x401): undefined reference to `typeinfo for Error'
MailBox.cpp:(.text+0x452): undefined reference to `Error::Error(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
MailBox.cpp:(.text+0x475): undefined reference to `Error::~Error()'
MailBox.cpp:(.text+0x47d): undefined reference to `typeinfo for Error'
MailBox.cpp:(.text+0x50a): undefined reference to `Error::Error(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
MailBox.cpp:(.text+0x52d): undefined reference to `Error::~Error()'
MailBox.cpp:(.text+0x535): undefined reference to `typeinfo for Error'
MailBox.cpp:(.text+0x6af): undefined reference to `Error::Error(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
MailBox.cpp:(.text+0x6d2): undefined reference to `Error::~Error()'
MailBox.cpp:(.text+0x6da): undefined reference to `typeinfo for Error'
MailBox.cpp:(.text+0x854): undefined reference to `Error::Error(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
MailBox.cpp:(.text+0x877): undefined reference to `Error::~Error()'
MailBox.cpp:(.text+0x87f): undefined reference to `typeinfo for Error'
MailBox.cpp:(.text+0x923): undefined reference to `Error::Error(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
MailBox.cpp:(.text+0x946): undefined reference to `Error::~Error()'
MailBox.cpp:(.text+0x94e): undefined reference to `typeinfo for Error'
MailBox.cpp:(.text+0x9b6): undefined reference to `Error::Error(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
MailBox.cpp:(.text+0x9d9): undefined reference to `Error::~Error()'
MailBox.cpp:(.text+0x9e1): undefined reference to `typeinfo for Error'
collect2: ld returned 1 exit status

I've already used this Error class for another project, and it worked well. I don't understand why here it doesn't work.

Upvotes: 0

Views: 1135

Answers (1)

Andy Prowl
Andy Prowl

Reputation: 126522

This is not a compilation error, this is a linker error. Basically, this error is informing you that a definition for some your functions is missing.

Reading from the linker's output, it is evident that those functions are the copy constructor and the destructor of class Error.

This is compatible with the fact that you are showing just a declaration of those function (in the class definition for Error). You should also provide a definition for them. For instance, you could simply inline those definitions:

class Error : public std::exception
{
public:
    Error(const std::string& s) throw() : _msg(s) { }
    ~Error() throw() { };
    const char*   what() const throw() { return _msg.c_str(); };
private:
    std::string _msg;
};

Upvotes: 3

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