gcc/cp/NEWS

*** Changes since G++ version 2.7.2:

* A public review copy of the December 1996 Draft of the ANSI C++
  proto-standard is now available. See

	http://www.cygnus.com/misc/wp/

  for more information.

* Default function arguments in templates will not be evaluated (or
  checked for semantic validity) unless they are needed.

* The -ftemplate-depth-NN flag can be used to increase the maximum
  recursive template instantiation depth, defaulting to 17. If you need
  to use this flag, the compiler will tell you.

* The internal interface between RTTI-using code and the RTTI support
  library has changed, so code that uses dynamic_cast should be
  recompiled. The RTTI support library has moved from libstdc++ to
  libgcc, so you no longer need to link against libstdc++ for a program
  that doesn't use the "hosted" library.

* bool is now always the same size as another built-in type. Previously,
  a 64-bit RISC target using a 32-bit ABI would have 32-bit pointers and a
  64-bit bool. This should only affect Irix 6, which was not supported in
  2.7.2.

* new (nothrow) is now supported.

* A flag -Weffc++ has been added for violations of some of the style 
  guidelines in Scott Meyers' _Effective C++_ books.

* On ELF systems, duplicate copies of symbols with 'initialized common'
  linkage (such as template instantiations, vtables, and extern inlines)
  will now be discarded by the GNU linker, so you don't need to use -frepo.
  This support requires GNU ld from binutils 2.8 or later.

* Partial specialization of class templates is now supported.

* The overload resolution code has been rewritten to conform to the latest
  C++ Working Paper.  Built-in operators are now considered as candidates
  in operator overload resolution.  Function template overloading chooses
  the more specialized template, and handles base classes in type deduction
  and guiding declarations properly.  In this release the old code can
  still be selected with -fno-ansi-overloading, although this is not
  supported and will be removed in a future release.

* RTTI support has been rewritten to work properly and is now on by default.
  This means code that uses virtual functions will have a modest space
  overhead.  You can use the -fno-rtti flag to disable RTTI support.

* Synthesized destructors are no longer made virtual just because the class
  already has virtual functions, only if they override a virtual destructor
  in a base class.  The compiler will warn if this affects your code.

* The g++ driver no longer links with libg++ by default; it is now
  functionally identical to the c++ driver.

* (void *)0 is no longer considered a null pointer constant; NULL in
  <stddef.h> is now defined as __null, a magic constant of type (void *)
  normally, or (size_t) with -ansi.

* The new 'template <>' specialization syntax is now accepted and ignored.

* The name of a class is now implicitly declared in its own scope; A::A
  refers to A.

* g++ now uses a new implementation of templates. The basic idea is that
  now templates are minimally parsed when seen and then expanded later.
  This allows conformant early name binding and instantiation controls,
  since instantiations no longer have to go through the parser.

  What you get:

     + Inlining of template functions works without any extra effort or
       modifications.
     + Instantiations of class templates and methods defined in the class
       body are deferred until they are actually needed (unless
       -fexternal-templates is specified).
     + Nested types in class templates work.
     + Static data member templates work.

  Possible problems:

     + Types and class templates used in templates must be declared
       first, or the compiler will assume they are not types, and fail.
     + Similarly, nested types of template type parameters must be tagged
       with the 'typename' keyword.  In many cases, the compiler will tell
       you where you need to add 'typename'.
     + Syntax errors in templates that are never instantiated will now be
       diagnosed.

* Synthesized methods are now emitted in any translation units that need
  an out-of-line copy. They are no longer affected by #pragma interface
  or #pragma implementation.

* Local classes are now supported.

* -Wall no longer implies -W.
  The new warning flag, -Wsign-compare, included in -Wall, warns about
  dangerous comparisons of signed and unsigned values. Only the flag is
  new; it was previously part of -W.

* The new flag, -fno-weak, disables the use of weak symbols.

* __attribute__ can now be attached to types as well as declarations.

* -Woverloaded-virtual now warns if a virtual function in a base class is
  hidden in a derived class, rather than warning about virtual functions
  being overloaded (even if all of the inherited signatures are
  overridden) as it did before.

* The compiler no longer emits a warning if an ellipsis is used as a
  function's argument list.

* Exception handling support has been significantly improved and is on by
  default.  This can result in significant runtime overhead.  You can turn
  it off with -fno-exceptions.

* Definition of nested types outside of their containing class is now
  supported. Use the following source code, as an example.

       struct A {
              struct B;
              B* bp;
       };

       struct A::B {
              int member;
       };

* Explicit instantiation of template constructors and destructors is now
  supported. Use the following source code, as an example.

       template A<int>::A(const A&);

* On the HPPA, some classes that do not define a copy constructor
  will be passed and returned in memory again so that functions
  returning those types can be inlined.