[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: 20000802: netcdf 3.5-beta3 installation problem on IBM SP

>From: Harsh Anand <address@hidden>
>Subject: Re: 20000802: netcdf 3.5-beta3 installation problem on IBM SP
>Organization: LBNL/NERSC
>Keywords: 200008022147.e72LljT08254 netCDF 3.5-beta3 C++ friend

Harsh,

> Sorry for getting back to you this late.  It took  very long to
> get the standard reference from the IBM tech support.
> Please let me know if this answers your query.

Thanks for sending this.  It does answer my question, so I've changed
the code in netCDF 3.5 as a result.  Now it should compile on IBM
platforms without the C++ error you were seeing.  It will be in the
next beta release, which I'm hoping to get out this week or early next
week ...

--Russ

 Here is their  response:

 >where in the standard the following syntax is disallowed:
 >friend NcFile::NcFile( const char *, FileMode, size_t*, size_t);

 "The solution to your question is the following section
 of the C++ Standard 12.1, paragraph 1.
 "Constructors do not have names."  Reading further into this paragraph
 it states that a constructor is indicated with a special syntax.
 "friend" is not in this syntax so it cannot be used in a constructor
 declaration/definition.  Thus, it is impossible to have a constructor
 that is a friend.  That said, the same effect can be had by making the
 class (for the constructor) a friend so that the constructor would also
 be granted friendship."

 For your reference here is the URL for the  C++ standard:

 http://www.dfv.rwth-aachen.de/doc/c++std/special.html#class.conv.ctor

 Regards.

 Harsh

 > >From: Harsh Anand <address@hidden>
 > >Subject: netcdf 3.5-beta3 installation problem on IBM SP
 > >Organization: LBNL/NERSC
 > >Keywords: 200008022147.e72LljT08254 netCDF 3.5-beta3
 >
 > Hi Harsh,
 >
 > > I got  errors like
 > >
 > >        xlC -c  -I../libsrc -I.  -DNDEBUG netcdf.cpp
 > > "netcdfcpp.h", line 156.10: 1540-0133 (S) The attributes "friend" are
 > > not allowed.
 > >
 > > installing C++ interface on the IBM SP3  we have at NERSC Lawrence
 > > Berkeley Lab:
 > >
 > >  FYI  -- IBM tech support folks tell me that  it is not a bug. According
 > > to the
 > > standard   "The attributes "friend" are not allowed".    Could you
 > > please suggest any workaround for this problem?
 > > I have successfully compiled this program using  KAI C++ compiler.
 >
 > See a previous message for a workaround:
 >
 >   http://www.unidata.ucar.edu/glimpse/netcdf/3814
 >
 > But I don't understand how this could be non-standard C++.  The draft
 > standard available from
 >
 >   http://www.cygnus.com/misc/wp/dec96pub/access.html includes the
 >
 > following example:
 >
 >  4 When a friend declaration refers to an overloaded  name  or  operator,
 >    only  the  function specified by the parameter types becomes a friend.
 >    A member function of a class X can be a friend of a class  Y.   [Exam-
 >    ple:
 >            class Y {
 >                friend char* X::foo(int);
 >                // ...
 >            };
 >
 > which uses the same syntax we use.  Is it that you can't declare a
 > private constructor to be a friend?  If so, I haven't seen that
 > restriction explicitly stated anywhere.  Can you find out where in the
 > standard this syntax is disallowed, since no other C++ compiler we
 > have tried objects to it?
 >
 > A less heavy-handed workaround would be to declare the whole NcFile
 > class to be a friend rather than just particular member functions,
 > that is use
 >
 >   friend NcFile;
 >
 > instead of
 >
 >   friend NcFile::NcFile( const char *, FileMode, size_t*, size_t);
 >   friend NcBool NcFile::sync( void );
 >   friend NcDim* NcFile::add_dim( NcToken, long );
 >     // to delete dimensions, since destructor is private
 >   friend NcBool NcFile::close( void );
 >
 > and similarly for other places where the compiler objects to the
 > declarations of particular member functions as friends.  But I don't
 > understand why this should be necessary ...
 >
 > --Russ

 --
  Harsh Anand ----------------------------------   address@hidden  -|
  NERSC User Services                      phone:  (510) 486-5575   |
  Lawrence Berkeley Lab                      Fax:  (510) 486-7520   |
  Univ. of California, Berkeley ------------------------------------