Re: [Opencxx-users] Problem compiling OpenC++ on Cygwin.

[Jonathan G. <gt...@ma...>]

Peter C. Chapin wrote:

> Hello!
>
> I'm attempting to compile OpenC++ under Cygwin on my Windows XP
> machine. The compile is failing during the processing of driver.cc
> with the following message:
>
> /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::Meta
> compilerConfiguration::IteratorIface]' discards qualifiers
>
> It looks like I'm trying to convert a const auto_ptr to an
> auto_ptr_ref and gcc isn't going for it. I'm using v3.4.4 and I'm
> wondering if perhaps the code was originally written for an older
> version of the compiler. Would I be better advised to use the CVS
> version over the current official version? The message above came
> during an attempt to compile v2.8.
>
> Thanks!
>
> Peter
>
>
>
> -------------------------------------------------------
> This SF.net email is sponsored by: Splunk Inc. Do you grep through log
> files
> for problems?  Stop!  Download the new AJAX search engine that makes
> searching your log files as easy as surfing the  web.  DOWNLOAD SPLUNK!
> http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click
> _______________________________________________
> Opencxx-users mailing list
> Ope...@li...
> https://lists.sourceforge.net/lists/listinfo/opencxx-users
>
Hi,

I had a similar problem when I first started using it.  Scott D. Fleming
gave me the following advice:

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


Afterwards, it solved the compile problem but still did not work.  I had
to get his version on OpenC++ before it started working. 

Good Luck,

-- 
Jonathan Gdalevich
Georgia Institute of Technology, Atlanta Georgia, 30332
Email: gt...@pr...