*** Changes since G++ version 2.7.2:
-* A public review copy of the December 1996 Draft of the ANSI C++
+* 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.
-* Member function templates are now supported.
+* 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 -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).
+* 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.
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 (libc 6 on x86).
+ Linux with glibc 2.x (also called libc 6.x).
-* 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.
+* 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
* 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
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.
<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.
-
- Still not supported:
-
- + Member class templates.
- + Template template parameters.
-
-* 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.
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.
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