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*** Changes in GCC 3.4:

* Changes in GCC 3.4 are described in 'gcc-3.4/changes.html'

*** Changes in GCC 3.3:

* The "new X = 3" extension has been removed; you must now use "new X(3)".

* G++ no longer allows in-class initializations of static data members

  that do not have arithmetic or enumeration type.  For example:

    struct S {

      static const char* const p = "abc";

    };

  is no longer accepted.

  Use the standards-conformant form:

    struct S {

      static const char* const p;

    };

    const char* const S::p = "abc";

  instead.

  (ISO C++ is even stricter; it does not allow in-class

  initializations of floating-point types.)

*** Changes in GCC 3.1:

* -fhonor-std and -fno-honor-std have been removed. -fno-honor-std was

  a workaround to allow std compliant code to work with the non-std

  compliant libstdc++-v2. libstdc++-v3 is std compliant.

* The C++ ABI has been fixed so that `void (A::*)() const' is mangled as

  "M1AKFvvE", rather than "MK1AFvvE" as before.  This change only affects

  pointer to cv-qualified member function types.

* The C++ ABI has been changed to correctly handle this code:

    struct A {

      void operator delete[] (void *, size_t);

    };

    struct B : public A {

    };

    new B[10];

  The amount of storage allocated for the array will be greater than

  it was in 3.0, in order to store the number of elements in the

  array, so that the correct size can be passed to `operator delete[]'

  when the array is deleted.  Previously, the value passed to

  `operator delete[]' was unpredictable.

  This change will only affect code that declares a two-argument

  `operator delete[]' with a second parameter of type `size_t'

  in a base class, and does not override that definition in a

  derived class.

* The C++ ABI has been changed so that:

    struct A {

      void operator delete[] (void *, size_t);

      void operator delete[] (void *);

    };

  does not cause unnecessary storage to be allocated when an array of

  `A' objects is allocated.

  This change will only affect code that declares both of these

  forms of `operator delete[]', and declared the two-argument form

  before the one-argument form.

* The C++ ABI has been changed so that when a parameter is passed by value,

  any cleanup for that parameter is performed in the caller, as specified

  by the ia64 C++ ABI, rather than the called function as before.  As a

  result, classes with a non-trivial destructor but a trivial copy

  constructor will be passed and returned by invisible reference, rather

  than by bitwise copy as before.

* G++ now supports the "named return value optimization":  for code like

    A f () {

      A a;

      ...

      return a;

    }

  G++ will allocate 'a' in the return value slot, so that the return

  becomes a no-op.  For this to work, all return statements in the function

  must return the same variable.

*** Changes in GCC 3.0:

* Support for guiding declarations has been removed.

* G++ now supports importing member functions from base classes with a

  using-declaration.

* G++ now enforces access control for nested types.

* In some obscure cases, functions with the same type could have the

  same mangled name.  This bug caused compiler crashes, link-time clashes,

  and debugger crashes.  Fixing this bug required breaking ABI

  compatibility for the functions involved.  The functions in questions

  are those whose types involve non-type template arguments whose

  mangled representations require more than one digit.

* Support for assignment to `this' has been removed.  This idiom

  was used in the very early days of C++, before users were allowed

  to overload `operator new'; it is no longer allowed by the C++

  standard.

* Support for signatures, a G++ extension, have been removed.

* Certain invalid conversions that were previously accepted will now

  be rejected.  For example, assigning function pointers of one type

  to function pointers of another type now requires a cast, whereas

  previously g++ would sometimes accept the code even without the

  cast.

* G++ previously allowed `sizeof (X::Y)' where Y was a non-static

  member of X, even if the `sizeof' expression occurred outside

  of a non-static member function of X (or one of its derived classes,

  or a member-initializer for X or one of its derived classes.)   This

  extension has been removed.

* G++ no longer allows you to overload the conditional operator (i.e.,

  the `?:' operator.)

* The "named return value" extension:

    int f () return r { r = 3; }

  has been deprecated, and will be removed in a future version of G++.

*** Changes in GCC 2.95:

* Messages about non-conformant code that we can still handle ("pedwarns")

  are now errors by default, rather than warnings.  This can be reverted

  with -fpermissive, and is overridden by -pedantic or -pedantic-errors.

* String constants are now of type `const char[n]', rather than `char[n]'.

  This can be reverted with -fno-const-strings.

* References to functions are now supported.

* Lookup of class members during class definition now works in all cases.

* In overload resolution, type conversion operators are now properly

  treated as always coming from the most derived class.

* C9x-style restricted pointers are supported, using the `__restrict'

  keyword.

* You can now use -fno-implicit-inline-templates to suppress writing out

  implicit instantiations of inline templates.  Normally we do write them

  out, even with -fno-implicit-templates, so that optimization doesn't

  affect which instantiations are needed.

* -fstrict-prototype now also suppresses implicit declarations.

* Many obsolete options have been removed: -fall-virtual, -fmemoize-lookups,

  -fsave-memoized, +e?, -fenum-int-equivalence, -fno-nonnull-objects.

* Unused virtual functions can be discarded on some targets by specifying

  -ffunction-sections -fvtable-gc to the compiler and --gc-sections to the

  linker.  Unfortunately, this only works on Linux if you're linking

  statically.

* Lots of bugs stomped.

*** Changes in EGCS 1.1:

* Namespaces are fully supported.  The library has not yet been converted

  to use namespace std, however, and the old std-faking code is still on by

  default.  To turn it off, you can use -fhonor-std.

* Massive template improvements:

  + member template classes are supported.

  + template friends are supported.

  + template template parameters are supported.

  + local classes in templates are supported.

  + lots of bugs fixed.

* operator new now throws bad_alloc where appropriate.

* Exception handling is now thread safe, and supports nested exceptions and

  placement delete.  Exception handling overhead on x86 is much lower with

  GNU as 2.9.

* protected virtual inheritance is now supported.

* Loops are optimized better; we now move the test to the end in most

  cases, like the C frontend does.

* For class D derived from B which has a member 'int i', &D::i is now of

  type 'int B::*' instead of 'int D::*'.

* An _experimental_ new ABI for g++ can be turned on with -fnew-abi.  The

  current features of this are more efficient allocation of base classes

  (including the empty base optimization), and more compact mangling of C++

  symbol names (which can be turned on separately with -fsquangle).  This

  ABI is subject to change without notice, so don't use it for anything

  that you don't want to rebuild with every release of the compiler.

  As with all ABI-changing flags, this flag is for experts only, as all

  code (including the library code in libgcc and libstdc++) must be

  compiled with the same ABI.

*** Changes in EGCS 1.0:

* A public review copy of the December 1996 Draft of the ISO/ANSI C++

  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.

     + Explicit specification of template parameters to function templates

       is now supported.

  Things you may need to fix in your code:

     + Syntax errors in templates that are never instantiated will now be

       diagnosed.

     + 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, except in base lists.  In many cases,

       but not all, the compiler will tell you where you need to add

       'typename'.  For more information, see

            http://www.cygnus.com/misc/wp/dec96pub/template.html#temp.res

     + Guiding declarations are no longer supported.  Function declarations,

       including friend declarations, do not refer to template instantiations.

       You can restore the old behavior with -fguiding-decls until you fix

       your code.

  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, which defaults to 17. If you

       need to use this flag, the compiler will tell you.

     + Explicit instantiation of template constructors and destructors is

       now supported.  For instance:

            template A::A(const A&);

  Still not supported:

     + Member class templates.

     + Template friends.

* Exception handling support has been significantly improved and is on by

  default.  The compiler supports two mechanisms for walking back up the

  call stack; one relies on static information about how registers are

  saved, and causes no runtime overhead for code that does not throw

  exceptions.  The other mechanism uses setjmp and longjmp equivalents, and

  can result in quite a bit of runtime overhead.  You can determine which

  mechanism is the default for your target by compiling a testcase that

  uses exceptions and doing an 'nm' on the object file; if it uses __throw,

  it's using the first mechanism.  If it uses __sjthrow, it's using the

  second.

  You can turn EH support off with -fno-exceptions.

* 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.

* 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.

* 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.

* Standard usage syntax for the std namespace is supported; std is treated

  as an alias for global scope.  General namespaces are still not supported.

* New flags:

     + New warning -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.

* 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.

* __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.

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

  translation units.

* -fvtable-thunks is supported for all targets, and is the default for

  Linux with glibc 2.x (also called libc 6.x).

* 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.

* 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

   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.  For instance:

       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.

*** The g++ team thanks everyone that contributed to this release,

    but especially:

* Joe Buck , the maintainer of the g++ FAQ.

* Brendan Kehoe , who coordinates testing of g++.

* Jason Merrill , the g++ maintainer.

* Mark Mitchell , who implemented member function

  templates and explicit qualification of function templates.

* Mike Stump , the previous g++ maintainer, who did most of

  the exception handling work.

Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003,

2005 Free Software Foundation, Inc.

Copying and distribution of this file, with or without modification,

are permitted in any medium without royalty provided the copyright

notice and this notice are preserved.