gcc-3.1: problems with filebuf constructor for FILE*

[Scott Johnston]

I'm in the process of upgrading some C++ code that compiled under 
gcc-3.0.* to
gcc-3.1.  I am trying to migrate from using the basic_filebuf 
constructor that
accepted a FILE* to a new stdio_filebuf (from <ext/stdio_filebuf.h>), as 
explained
here:

http://gcc.gnu.org/onlinedocs/libstdc++/ext/howto.html#2

I find that __c_file_type (as used in <bits/basic_file.h>) is undefined 
when I
compile code that includes <ext/stdio_filebuf.h>.  Introducing my own
"#define __c_file_type std::__c_file" seems to fix that.

Then I run into the problem that <bits/basic_file.h> is looking for 
_M_cfile
member variable that is no longer there, as shown below (at the bottom
of this e-mail).  Adding my own
"#define _GLIBCPP_BASIC_FILE_ENCAPSULATION 1" seems to
alleviate that confusion.

Now I'm struggling with a conflict between const is_open methods at one 
level
that invoke non-const is_open methods, so I see the warning:

c++  -D__ACE_INLINE__  -gdwarf-2 -O2 -fPIC  -Dcplusplus_2_1 
-Wno-deprecated    -I/home/scott/src/ivtools-1.0/src/ComTerp/LINUX/.. 
-I/home/scott/src/ivtools-1.0/src/ComTerp/LINUX/../..  
-I/home/scott/src/ivtools-1.0/src  
-I/home/scott/src/ivtools-1.0/src/include 
-I/home/scott/src/ivtools-1.0/src/include/ivstd -I/usr/X11R6/include     
-c /home/scott/src/ivtools-1.0/src/ComTerp/LINUX/../comterpserv.c
/usr/local/include/g++-v3/fstream: In member function `bool
  std::basic_filebuf<_CharT, _Traits>::is_open() const [with _CharT = char,
  _Traits = std::char_traits<char>]':
/usr/local/include/g++-v3/ext/stdio_filebuf.h:97:   instantiated from 
`__gnu_cxx::stdio_filebuf<_CharT, 
_Traits>::stdio_filebuf(std::__c_file*, std::_Ios_Openmode, 
_Traits::int_type) [with _CharT = char, _Traits = std::char_traits<char>]'
/home/scott/src/ivtools-1.0/src/ComTerp/comterpserv.c:157:   
instantiated from here
/usr/local/include/g++-v3/fstream:110: passing `const 
std::__basic_file<char>'
  as `this' argument of `bool std::__basic_file<_CharT>::is_open() [with
  _CharT = char]' discards qualifiers

Are these all oversights in the stdio_filebuf extension that have been 
corrected
for gcc-3.1.1, or am I simply grabbing this completely backwards?  I 
haven't gotten
to linking yet, so I am also concerned with whether the _M_cfile member 
variable
will be there in the libstdc++-v3 object code.  Can anyone with better 
oversight of
this evolution (and these classes) lend me a clue?

Thanks,

Scott Johnston

p.s. as always I would suggest an alternate approach to clearing up this 
mess with
regards to iostreams and file descriptors would be to implement an 
extension that
is 100% backward compatible with libstdc++-v2.  I offer my source code
(http://www.ivtools.org) as a test-suite for such an approach, because I 
have
carefully preserved the prior style of iostreams/file-descriptor 
programming that
worked quite well for quite a while (and is still needed for all those 
out there who
haven't upgraded to a gcc-3.* compiler).


----------------------------------------------

compiling without "#define _GLIBCPP_BASIC_FILE_ENCAPSULATION 1"

c++  -D__ACE_INLINE__  -gdwarf-2 -O2 -fPIC  -Dcplusplus_2_1 
-Wno-deprecated    -I/home/scott/src/ivtools-1.0/src/ComTerp/LINUX/.. 
-I/home/scott/src/ivtools-1.0/src/ComTerp/LINUX/../..  
-I/home/scott/src/ivtools-1.0/src  
-I/home/scott/src/ivtools-1.0/src/include 
-I/home/scott/src/ivtools-1.0/src/include/ivstd -I/usr/X11R6/include     
-c /home/scott/src/ivtools-1.0/src/ComTerp/LINUX/../comterpserv.c
In file included from /usr/local/include/g++-v3/bits/basic_file.h:250,
                from /usr/local/include/g++-v3/fstream:48,
                from /usr/local/include/g++-v3/ext/stdio_filebuf.h:30,
                from 
/home/scott/src/ivtools-1.0/src/include/ivstd/fstream.h:9,
                from 
/home/scott/src/ivtools-1.0/src/ComTerp/comterpserv.c:35:
/usr/local/include/g++-v3/i686-pc-linux-gnu/bits/basic_file_model.h: In
  constructor `std::__basic_file<_CharT>::__basic_file(__c_lock*)':
/usr/local/include/g++-v3/i686-pc-linux-gnu/bits/basic_file_model.h:39: 
class `
  std::__basic_file<_CharT>' does not have any field named `_M_cfile'
/usr/local/include/g++-v3/i686-pc-linux-gnu/bits/basic_file_model.h:39: 
class `
  std::__basic_file<_CharT>' does not have any field named 
`_M_cfile_created'
/usr/local/include/g++-v3/i686-pc-linux-gnu/bits/basic_file_model.h: In 
member
  function `std::__basic_file<_CharT>*
  std::__basic_file<_CharT>::sys_open(std::__c_file*, std::_Ios_Openmode)
  [with _CharT = char]':
/usr/local/include/g++-v3/ext/stdio_filebuf.h:96:   instantiated from 
`__gnu_cxx::stdio_filebuf<_CharT, 
_Traits>::stdio_filebuf(std::__c_file*, std::_Ios_Openmode, 
_Traits::int_type) [with _CharT = char, _Traits = std::char_traits<char>]'
/home/scott/src/ivtools-1.0/src/ComTerp/comterpserv.c:157:   
instantiated from here
/usr/local/include/g++-v3/i686-pc-linux-gnu/bits/basic_file_model.h:87: `
  _M_cfile' undeclared (first use this function)
/usr/local/include/g++-v3/i686-pc-linux-gnu/bits/basic_file_model.h:87: 
(Each
  undeclared identifier is reported only once for each function it appears
  in.)