Re: [Opencxx-users] Make error under Cygwin

[Scott D. F. <sd...@ms...>]

Hi Jonathan,
I know what the problem is. First of all, here is the error message of interest:

  g++ -DHAVE_CONFIG_H -I. -I. -I.. -I. -I.. -g -O2 -MT driver.lo -MD -MP -MF 
.deps/driver.Tpo -c driver.cc  -DPIC -o .libs/driver.o
In file included from 
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/backward/strstream:51,
                  from driver.cc:47:
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/backward/backward_warning.h:32:2: 
warning: #warning This file includes at least one deprecated or antiquated 
header. Please consider using one of the 32 headers found in section 17.4.1.2 of 
the C++ standard. Examples include substituting the <X> header for the <X.h> 
header for C++ includes, or <iostream> instead of the deprecated header 
<iostream.h>. To disable this warning use -Wno-deprecated.
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_algobase.h: In function 
`void std::swap(_Tp&, _Tp&) [with _Tp = 
std::auto_ptr<Opencxx::MetacompilerConfiguration::IteratorIface>]':
../opencxx/MetacompilerConfiguration.h:50:   instantiated from here
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_algobase.h:132: error: 
passing `const std::auto_ptr<Opencxx::MetacompilerConfiguration::IteratorIface>' 
as `this' argument of `std::auto_ptr<_Tp>::operator std::auto_ptr_ref<_Tp1>() 
[with _Tp1 = Opencxx::MetacompilerConfiguration::IteratorIface, _Tp = 
Opencxx::MetacompilerConfiguration::IteratorIface]' discards qualifiers

The problem is that in gcc 3.4.x std::auto_ptrs can't be swapped with std::swap. 
I assume this is a bug in the STL, and not a feature. The reason for the problem 
is that std::swap has a const tmp variable; i.e. (from bits/stl_algobase.h):

   template<typename _Tp>
     inline void
     swap(_Tp& __a, _Tp& __b)
     {
       // concept requirements
       __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)

       const _Tp __tmp = __a; // <---THIS CAUSES std::auto_ptr PROBLEMS
       __a = __b;
       __b = __tmp;
     }

And std::auto_ptr's auto_ptr_ref operator, which is called in the const line 
above, is a non-const method; i.e. (from memory.h):

   template<typename _Tp>
     class auto_ptr
     {
       ...
       template<typename _Tp1>
         operator auto_ptr_ref<_Tp1>() throw()
         { return auto_ptr_ref<_Tp1>(this->release()); }
       ...

My solution to the problem was add my own swap function to the OpenC++ code, and 
  use it to swap std::auto_ptrs. To accomplish this, I edited the 
MetacompilerConfiguration.h file in the OpenC++ source. I added this function 
definition near the top of the file just under "class ErrorLog":

   template<class T>
   inline void
   MYswap(std::auto_ptr<T>& a, std::auto_ptr<T>& b)
   {
     std::auto_ptr<T> c = a;
     a = b;
     b = c;
   }

Next (in the same file), I changed class MetacompilerConfiguration::Iterator 
(found in the public section of class MetacompilerConfiguration), so that its 
operator= went from:

         Iterator& operator=(Iterator iter)
         {
             std::swap(impl_, iter.impl_);
             return *this;
         }

To:

         Iterator& operator=(Iterator iter)
         {
             MYswap(impl_, iter.impl_);
             return *this;
         }

And this solved the problem for me, and I expect it will for you as well.

Now, I must warn you that there is another problem you will encounter with 
OpenC++ once you have built it. There is a mistake in the grammar that OpenC++'s 
parser expects. Prior to GCC 3.4, this was never a problem, but since GCC 3.4, 
the STL library uses the syntax that the broken grammar doesn't accept. In 
particular OpenC++ expects template declarations to look like this:

   template<typename T>...

With an identifier like "T" following typename, but in fact the following is 
legal C++:

   template<typename>...

This causes occ to issue errors whenever it parses the GCC library files that 
include the latter syntax (e.g., bits/cpp_type_traits.h). I fixed the problem by 
changing the Parser::rTempArgDeclaration member function definition in 
parser/Parser.cc. I changed this line (roughly the third line in the function):

     if(t0 == CLASS && lex->LookAhead(1) == Identifier){

To this:

     if(t0 == CLASS && !(lex->LookAhead(1) == Identifier)){
         lex->GetToken(tk1);
         decl = PtreeUtil::List(new Leaf(tk1));
     }
     else if(t0 == CLASS && lex->LookAhead(1) == Identifier){

I am not positive that my Ptree representation for the template argument 
declaration (temp.arg.declaration) is exactly what the OpenC++ maintainers would 
want, but it seemed to make sense to me.

Anyway, I hope these fixes help you get OpenC++ running. I've been using it for 
a couple of years, and it's really a lovely tool.
Cheers, Scott

PS: There is one other fix that you will probably want to apply, found in:

	http://sourceforge.net/mailarchive/message.php?msg_id=9785370



Jonathan Gdalevich wrote:
> Dear OpenC++ users,
> 
> I am trying to make the latest version of OpenC++ (2.8) in Cygwin with
> gcc (3.4.4) and all latest updates and getting an error during make. 
> Attached are my configure and make log files along with the Makefile.
> 
> Sincerely,
> 
>