[boost] [serialization] add_facet, VC7.1, and overloading operator new

21 Jun 2005

      Hi,

  I've been playing around with overloading global operator new and 
delete and came across a problem concerning facets with VC7.1 in debug 
mode. Internally facets are reference counted and destroyed in 
[locale0.cpp - locale::_Locimp::~_Locimp()] via a macro _DELETE_CRT 
[xdebug]. Now when _DEBUG is defined this macro will not call 'operator 
delete' directly. So any facets added to a locale using 'operator new' 
will not be freed with 'operator delete'.

In my case this leads to an assertion in dbgheap.c. This is because the 
heap manager correctly recognizes that it was not responsible for the 
allocation.

boost/archive/impl/basic_text_iprimitive.ipp:
   add_facet(
      std::locale::classic(),
      new codecvt_null<BOOST_DEDUCED_TYPENAME IStream::char_type>
   )

Minimal example is appended to the bottom of this post. As for a 
possible work around (read hack) you can use _NEW_CRT instead of new 
directly. A some what nicer hack^H^H^H^Hsolution may be to get add_facet 
to perform the actual facet allocation itself using _NEW_CRT instead of 
the caller.

Chris Byrne

////////////////////////////////////////////////////////////////////////////
#include <boost/archive/add_facet.hpp>
#include <boost/archive/codecvt_null.hpp>
#include <boost/shared_ptr.hpp>
#include <stdlib.h>
#include <malloc.h>

using namespace boost;
using namespace boost::archive;
using namespace std;

void* operator new(size_t size) {
    char* block = reinterpret_cast<char*>(malloc(size + 1));
    return block + 1;
}

void operator delete(void* address) {
    if (!address) return;
    char* block = reinterpret_cast<char*>(address);
    free(block - 1);
}

int main() {
    shared_ptr<locale> p;
    p.reset(
       add_facet(locale::classic(), new codecvt_null<char>)
//    add_facet(locale::classic(), _NEW_CRT codecvt_null<char>)
    );
    p.reset();
    return 0;
}