Boost C++ Libraries: Ticket #2984: Cannot serialize protected and private base classes

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Sat, 02 May 2009 17:56:04 GMT

attachment → boost_serialize_protected_bug_minimal.cc

Minimal code to reproduce the problem

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Sat, 02 May 2009 17:56:39 GMT

attachment → boost_serialize_protected_bug_minimal.compiler.output.txt

Compiler output when I try to compile the minimal code

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Sat, 02 May 2009 17:56:59 GMT

attachment → boost_serialize_protected_bug.cc

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Sat, 02 May 2009 17:58:37 GMT

attachment → boost_serialize_protected_bug.2.cc

Minimal code to reproduce the problem + some macros to test serializing through base pointer and public vs. private vs. protected access

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Sat, 02 May 2009 17:59:24 GMT

attachment → Makefile

Makefile I use to build the bug-reproducing code

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Sat, 02 May 2009 18:07:42 GMT

attachment → boost_serialize_protected_bug_minimal_2.cc

I removed one of the classes -- making the minimal even smaller

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Sat, 02 May 2009 18:08:23 GMT

attachment → Makefile.2

Updated makefile including _minimal_2

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Sat, 02 May 2009 18:08:56 GMT

attachment → boost_serialize_protected_bug_minimal_2.compiler.output.txt

Compiler output when I try to compile the smaller minimal code

status changed; resolution set

Robert Ramey — Mon, 18 May 2009 16:04:43 GMT

status new → closed
resolution → fixed

Fixed in trunk. Should be included with 1.40

status changed; resolution deleted

robtoth@… — Mon, 21 Jan 2013 21:53:14 GMT

status closed → reopened
resolution fixed

I just tried this on gcc 4.7 and the minimal example still doesn't compile. Was this ever fixed? Is there a workaround? The error is still "boost/serialization/void_cast.hpp:191: error: Base1 is an inaccessible base of Derived".

Robert Ramey — Tue, 22 Jan 2013 05:38:58 GMT

Replying to robtoth@…:

I made this program compile by adding

  friend class Derived;   // make Derived a friend
...
  virtual void print() const { // add "const" here
      cout << "Derived" << endl;
  }
...
  const Derived d;  // add "const" here

The addition of "const" is pretty obvious.

The addition of "friend" is not obvious and wouldn't seem necessary. On the other hand, I looked at the code and don't see an easy way to fix this.

Robert Ramey

robtoth@… — Thu, 24 Jan 2013 16:42:26 GMT

Sorry but I still can't compile this. The const is fine and I understand it, but the "friend" doesn't help.

boost_serialize_protected_bug_minimal_2.cc:

...
class Base1{
friend class boost::serialization::access;
friend class Derived; // Added this
...

I still get the error:

include/boost/serialization/smart_cast.hpp:204: error: 'Base1' is an inaccessible base of 'Derived'

This is on gcc svn trunk (2013-01-22, version 4.8) and boost svn trunk (as of 2013-01-22, version 1.53.0).

Did you do something different from what I did to make Derived serialize?

I can attach the full error output if it would help.

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Robert Ramey — Fri, 02 Oct 2015 00:34:38 GMT

attachment → test_private_base.cpp

serialization of private base class

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Robert Ramey — Fri, 02 Oct 2015 00:35:47 GMT

attachment → test_private_base2.cpp

cannot serialize through a private base class pointer

status changed; resolution set

Robert Ramey — Fri, 02 Oct 2015 00:41:20 GMT

status reopened → closed
resolution → invalid

OK _ looked at this more carefully.

There is more going on here than meets the eye.

test_private_base.cpp demonstrates that one can serialize a private base class with no problem.

test_private_base.cpp demonstrates the problem which occurs when one tries to serialized through a pointer to a private base class. The program fails to compile at line 90. Basically one cannot do this in C++. I've searched in vain for a way to do this but haven't found any. The BOOST_CLASS_EXPORT uses the same functionality to implement this facility so it has the same problem.

Bottom line - serializatiion of private/protected base classes is fine - but one cannot serialize such classes through a base class pointer.