experimental C++0x mode in GCC@. The C++0x mode in GCC tracks the draft
working paper for the C++0x standard; the latest working paper is
available on the ISO C++ committee's web site at
-@uref{http://www.open-std.org/jtc1/sc22/wg21/}. For information
+@uref{http://www.open-std.org/@/jtc1/@/sc22/@/wg21/}. For information
regarding the C++0x features available in the experimental C++0x mode,
-see @uref{http://gcc.gnu.org/gcc-4.3/cxx0x_status.html}. To select this
+see @uref{http://gcc.gnu.org/projects/@/cxx0x.html}. To select this
standard in GCC, use the option @option{-std=c++0x}; to obtain all the
diagnostics required by the standard, you should also specify
@option{-pedantic} (or @option{-pedantic-errors} if you want them to be
@cindex Objective-C
@cindex Objective-C++
-There is no formal written standard for Objective-C or Objective-C++@. The most
-authoritative manual is ``Object-Oriented Programming and the
-Objective-C Language'', available at a number of web sites:
+GCC supports ``traditional'' Objective-C (also known as ``Objective-C
+1.0'') and contains support for the Objective-C exception and
+synchronization syntax. It has also support for a number of
+``Objective-C 2.0'' language extensions, including properties, fast
+enumeration (only for Objective-C), method attributes and the
+@@optional and @@required keywords in protocols. GCC supports
+Objective-C++ and features available in Objective-C are also available
+in Objective-C++@.
+GCC by default uses the GNU Objective-C runtime library, which is part
+of GCC and is not the same as the Apple/NeXT Objective-C runtime
+library used on Apple systems. There are a number of differences
+documented in this manual. The options @option{-fgnu-runtime} and
+@option{-fnext-runtime} allow you to switch between producing output
+that works with the GNU Objective-C runtime library and output that
+works with the Apple/NeXT Objective-C runtime library.
+
+There is no formal written standard for Objective-C or Objective-C++@.
+The authoritative manual on traditional Objective-C (1.0) is
+``Object-Oriented Programming and the Objective-C Language'',
+available at a number of web sites:
@itemize
@item
-@uref{http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/ObjectiveC/}
-is a recent (and periodically updated) version;
+@uref{http://www.gnustep.org/@/resources/@/documentation/@/ObjectivCBook.pdf}
+is the original NeXTstep document;
@item
@uref{http://objc.toodarkpark.net}
-is an older example;
+is the same document in another format;
@item
-@uref{http://www.gnustep.org}
-and
-@uref{http://gcc.gnu.org/readings.html}
-have additional useful information.
+@uref{http://developer.apple.com/@/mac/@/library/@/documentation/@/Cocoa/@/Conceptual/@/ObjectiveC/}
+has an updated version but make sure you search for ``Object Oriented Programming and the Objective-C Programming Language 1.0'',
+not documentation on the newer ``Objective-C 2.0'' language
@end itemize
+The Objective-C exception and synchronization syntax (that is, the
+keywords @@try, @@throw, @@catch, @@finally and @@synchronized) is
+supported by GCC and is enabled with the option
+@option{-fobjc-exceptions}. The syntax is briefly documented in this
+manual and in the Objective-C 2.0 manuals from Apple.
+
+The Objective-C 2.0 language extensions and features are automatically
+enabled; they include properties (via the @@property, @@synthesize and
+@@dynamic keywords), fast enumeration (not available in
+Objective-C++), attributes for methods (such as deprecated, noreturn,
+sentinel, format), the unused attribute for method arguments, the
+@@package keyword for instance variables and the @@optional and
+@@required keywords in protocols. You can disable all these
+Objective-C 2.0 language extensions with the option
+@option{-fobjc-std=objc1}, which causes the compiler to recognize the
+same Objective-C language syntax recognized by GCC 4.0, and to produce
+an error if one of the new features is used.
+
+GCC has currently no support for non-fragile instance variables.
+
+The authoritative manual on Objective-C 2.0 is available from Apple:
+@itemize
+@item
+@uref{http://developer.apple.com/@/mac/@/library/@/documentation/@/Cocoa/@/Conceptual/@/ObjectiveC/}
+@end itemize
+
+For more information concerning the history of Objective-C that is
+available online, see @uref{http://gcc.gnu.org/readings.html}
+
+@section Go language
+
+The Go language continues to evolve as of this writing; see the
+@uref{http://golang.org/@/doc/@/go_spec.html, current language
+specifications}. At present there are no specific versions of Go, and
+there is no way to describe the language supported by GCC in terms of
+a specific version. In general GCC tracks the evolving specification
+closely, and any given release will support the language as of the
+date that the release was frozen.
+
+@section References for other languages
+
@xref{Top, GNAT Reference Manual, About This Guide, gnat_rm,
GNAT Reference Manual}, for information on standard
conformance and compatibility of the Ada compiler.
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