What's new in version 2.7.x of gcc/g++
======================================

   The current version of gcc/g++ is 2.7.2; the current libg++ is 2.7.1.

   By the time you read this, two minor bug-fix releases, gcc 2.7.3 and
libg++ 2.7.2, may be available.  These new releases are mainly intended
to fix platform-specific bugs and do not affect the C++ "front end" of
the compiler.

   The 2.7.x releases represent a great deal of work on the part of the
g++ maintainers to fix outstanding bugs and move the compiler closer to
the current ANSI/ISO standards committee's working paper, including
supporting many of the new features that have been added to the
language.  I recommend that everyone read the NEWS file contained in the
distribution (and that system administrators make the file available to
their users).  I've borrowed liberally from this file here.

   If any features seem unfamiliar, you will probably want to look at
the recently-released public review copy of the C++ Working Paper:
   * PostScript and PDF (Adobe Acrobat): see
     `ftp://research.att.com/dist/c++std/WP'.

   * HTML and ASCII versions: see `ftp://ftp.cygnus.com/pub/g++'.

   * World Wide Web: see `http://www.cygnus.com/misc/wp/'.

   Here are the main points:

   * As described above, the scope of variables declared in the
     initialization part of a for statement has been changed; such
     variables are now visible only in the loop body.  Use
     `-fno-for-scope' to get the old behavior.  You'll need this flag
     to build groff version 1.09, Ptolemy, and many other free software
     packages.

   * Code that does not use #pragma interface/implementation will most
     likely shrink dramatically, as g++ now only emits the vtable for a
     class in the translation unit where its first non-inline,
     non-abstract virtual function is defined.

   * Support for automatic template instantiation has *not* been enabled
     in the official distribution, due to a disagreement over design
     philosophies.  But you can get a patch from Cygnus to turn it on;
     retrieve the patch from
     `ftp://ftp.cygnus.com/pub/g++/gcc-2.7.2-repo.gz' to patch
     gcc-2.7.2 (there are also patches for earlier gcc versions).

   * See exceptions

   * Support for Run-Time Type Identification has been added with
     `-frtti'.  This support is still in alpha; one major restriction
     is that any file compiled with `-frtti' must include `<typeinfo>'
     (*not* `typeinfo.h' as the NEWS file says).  Also, all code you
     link with (including libg++) has to be built with `-frtti', so
     it's still tricky to use.

   * Synthesis of compiler-generated constructors, destructors and
     assignment operators is now deferred until the functions are used.

   * The parsing of expressions such as `a ? b : c = 1' has changed from
     `(a ? b : c) = 1' to `a ? b : (c = 1)'.  This is a new C/C++
     incompatibility brought to you by the ANSI/ISO standards committee.

   * The operator keywords and, and_eq, bitand, bitor, compl, not,
     not_eq, or, or_eq, xor and xor_eq are now supported.  Use `-ansi'
     or `-foperator-names' to enable them.

   * The `explicit' keyword is now supported.  `explicit' is used to
     mark constructors and type conversion operators that should not be
     used implicitly.

   * Handling of user-defined type conversion has been improved.

   * Explicit instantiation of template methods is now supported.  Also,
     `inline template class foo<int>;' can be used to emit only the
     vtable for a template class.

   * With -fcheck-new, g++ will check the return value of all calls to
     operator new, and not attempt to modify a returned null pointer.

   * collect2 now demangles linker output, and c++filt has become part
     of the gcc distribution.

   * Improvements to template instantiation: only members actually used
     are instantiated.  (Actually this is not quite true: some inline
     templates that are not successfully inlined may be expanded even
     though they are not needed).