gcc/cp/NEWS

[Joe Buck <jbuck at synopsys dot com>]

I wasn't satisfied with gcc/cp/NEWS, so I took a shot at re-organizing it.
The main re-org is to collect all the template information together and
put it at the top (since I think it's the proudest achievement of the
new front end); I also grouped the new flags together, tried to put
related changes next to each other (eg RTTI) and fixed a couple
of minor goofs.

The whole file's no bigger than the diff, so here it is:
----------
*** Changes since G++ version 2.7.2:

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

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

  for more information.

* 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.

     + Member function templates are now supported.

     + Partial specialization of class templates is now supported.

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

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

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

  Possible problems (caused by complying with the ANSI/ISO draft):

     + 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.

  Other features:

     + Default function arguments in templates will not be evaluated (or
       checked for semantic validity) unless they are needed.  Default
       arguments in class bodies will not be parsed until the class
       definition is complete.

     + 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.

  Still not supported:

     + Template template parameters.

* 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.

* 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.

* 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.

* __FUNCTION__ and __PRETTY_FUNCTION__ are now treated as variables by the
  parser; previously they were treated as string constants.  So code like
  `printf (__FUNCTION__ ": foo")' must be rewritten to 
  `printf ("%s: foo", __FUNCTION__)'.  This is necessary for templates.

* New flags:

     + New flags -Wsign-promo (warn about potentially confusing promotions
       in overload resolution), -Wno-pmf-conversion (don't warn about
       converting from a bound member function pointer to function pointer).

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

     + -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.

     + -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.

* local static variables in extern inline functions will be shared between
  translation units.

* Standard usage syntax for the std namespace is supported; std is treated
  as an alias for global scope.  General namespaces are still not supported.

* -fvtable-thunks is supported for all targets, and is the default for 
  Linux with glibc 2.x (also called libc 6.x).

* 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.

* 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.

* 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.

* 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 now only links against libstdc++, not libg++; it is
  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 name of a class is now implicitly declared in its own scope; A::A
  refers to A.

* Local classes are now supported.

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

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

* 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;
       };

* 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.