@setfilename g++FAQ.info
@settitle Frequently asked questions about the GNU C++ compiler
@setchapternewpage off
-@c version: @(#)g++FAQ.texi 1.56 09/15/97
+@c version: @(#)g++FAQ.texi 1.57 12/14/97
@c %**end of header
@iftex
@titlepage
@title G++ FAQ
@subtitle Frequently asked questions about the GNU C++ compiler
-@subtitle September 14, 1997
+@subtitle December 14, 1997
@sp 1
@author Joe Buck
@page
for doing the index. A hypertext version is available on the World Wide
Web at @file{http://www.cygnus.com/misc/g++FAQ_toc.html}.
-This document has just been reorganized a bit. There is some new
-information about upcoming g++ releases and egcs; more needs to be done
-but that will need to wait for next time. A diff would look misleadingly
-large, since I blew away and rebuilt the texinfo menus.
+@strong{News flash}: egcs has been released, and the 2.8.0 release is
+expected very soon!
Please send updates and corrections to the FAQ to
@code{jbuck@@synopsys.com}. Please do @emph{not} use me as a resource
to get your questions answered; that's what @file{gnu.g++.help} is for and I
-don't have the time to support the net's use of g++.
+don't have the time to support the net's use of g++. If you ignore this
+request your message to me may be deleted without a reply. Sorry.
Many FAQs, including this one, are available on the archive site
``rtfm.mit.edu''; see @*
@menu
* basics:: What is g++? How do I get it?
+* egcs and 2.8.0:: The next generation(s) of g++
* installation:: How to install, installation problems
* evolution:: The Evolution of g++
* User Problems:: Commonly reported problems and bugs
* g++ for other platforms::
* 1.x vs 2.x versions::
+The Next Generation(s) of g++
+
+* egcs-intro:: What is egcs?
+* egcs-whats-new:: What's new in egcs vs 2.7.2?
+* egcs-run-both:: How can I run both egcs and an FSF release?
+* egcs-vs-2.8.0:: How will egcs affect 2.8.0?
+* egcs-robustness:: How robust is egcs-1.0?
+
Installation Issues and Problems
* gcc-2 + g++-1::
The Evolution of g++
-* version 2.7.x::
+* version 2.7.x:: What's changed in 2.7.x from earlier versions
* libstdc++::
-* new work::
-* egcs::
-* When?::
User Problems
* assignment to streams::
@end menu
-@node basics, installation, Top, Top
+@node basics, egcs and 2.8.0, Top, Top
@chapter The basics: what is g++?
@cindex Free Software Foundation
@node latest versions, g++ for Unix, basics, basics
@section What is the latest version of gcc, g++, and libg++?
+@cindex egcs release
+
+The egcs project (on the Web: @file{http://www.cygnus.com/egcs/}) has
+now released egcs-1.0 as of December 3, 1997.
+
@cindex gcc/g++, version date
The current version of gcc/g++ is 2.7.2.3, released August 20, 1997.
Although that looks very recent, the only change is a minor patch to
One could argue that we shouldn't even refer to "g++-2.x.y" but it's a
convention. It means ``the C++ compiler included with gcc-2.x.y.''
-@node installation, evolution, basics, Top
+@node egcs and 2.8.0, installation, basics, Top
+@chapter The Next Generation(s) of g++
+
+@menu
+* egcs-intro:: What is egcs?
+* egcs-whats-new:: What's new in egcs vs 2.7.2?
+* egcs-run-both:: How can I run both egcs and an FSF release?
+* egcs-vs-2.8.0:: How will egcs affect 2.8.0?
+* egcs-robustness:: How robust is egcs-1.0?
+@end menu
+
+@node egcs-intro, egcs-whats-new, egcs and 2.8.0, egcs and 2.8.0
+@section What is egcs?
+
+egcs is the Experimental GNU compiler system (see
+@file{http://www.cygnus.com/egcs} on the Web). It is an effort to
+accelerate development of new gcc features by providing a more open
+development model than gcc has traditionally used.
+
+The first egcs release, egcs-1.0, came out on December 3, 1997.
+Questions not addressed here may be answered in the egcs FAQ
+(@file{http://www.cygnus.com/egcs/faq.html}).
+
+@node egcs-whats-new, egcs-run-both, egcs-intro, egcs and 2.8.0
+@section What new C++ features are in egcs?
+
+@strong{Note}: unless indicated otherwise, these features are expected
+to be present in g++ 2.8.0 when released.
+
+@itemize @bullet
+@item
+@cindex integrated libstdc++
+
+The standard C++ classes are integrated with the egcs release (this is
+@emph{not} expected to be true of gcc-2.8.0). libg++ is not being
+supported, though a version that will work with egcs has been
+contributed (FIXME: pointer?). The compiler and library are configured
+and built in one step.
+
+@item
+@cindex new template implementation
+A completely new template implementation, much closer to the draft
+standard. Limitations in 2.7.2.x concerning inlining template functions
+will be eliminated. Static template data members, template class member
+functions, partial specification, and default template arguments will be
+supported. An instantiation method resembling that used in Borland C++
+(instantiating functions possibly in multiple .o files and using weak
+symbols to link correctly) is provided, in addition to other
+options. The SGI version of STL is shipped verbatim with libstdc++.
+
+@item
+@cindex redundant template elimination
+@cindex templates: removing redundancy
+On ELF platforms (Linux/ELF, Solaris, SVR4), if the GNU linker is used,
+duplicated template functions and virtual function tables are eliminated
+at link time.
+
+@item
+@cindex repository
+@cindex -frepo
+The @code{-frepo} flag is supported in egcs (it will not be in 2.8.0).
+However, because of the previous item, I don't recommend its use on ELF
+systems.
+
+@item
+@cindex new exception implementation
+Exception handling has been re-worked; exceptions will work together
+with optimization.
+Actually, there are two separate implementations: one based on setjmp/longjmp
+and designed to be highly portable, and one designed to be more efficient but
+requiring more processor-specific support (getting exceptions right has proven
+to be extremely difficult and has been the chief obstacle to getting a new
+release out).
+
+@item
+@cindex RTTI
+RTTI has been re-done to work correctly and is on by default.
+
+@item
+@cindex overloading
+Overloading has been re-worked to conform to the latest draft of the
+standard.
+
+@item
+There are many more changes: see @file{http://www.cygnus.com/egcs/c++features.html} for a list.
+@end itemize
+
+Features that are still missing include namespaces and templates as
+template arguments.
+
+@node egcs-run-both, egcs-vs-2.8.0, egcs-whats-new, egcs and 2.8.0
+@section How can I run both egcs and an FSF release of g++ on the same machine?
+
+The recommended approach is to provide a different argument to the
+@code{--prefix} flag when you configure egcs. For example, say
+@code{--prefix=/usr/local/egcs} and then, after installation, you
+can make symbolic links from @file{/usr/local/egcs/bin} to whereever
+you want, for example
+
+@example
+ln -s /usr/local/egcs/bin/gcc /usr/local/bin/egcc
+ln -s /usr/local/egcs/bin/g++ /usr/local/bin/eg++
+@end example
+
+@node egcs-vs-2.8.0, egcs-robustness, egcs-run-both, egcs and 2.8.0
+@section What about 2.8.0? How does egcs affect the 2.8.x development?
+
+2.8.0 is expected Real Soon Now (I would guess by the end of 1997, but that
+is only a guess). The C++ front end should be essentially the same.
+
+Bug fixes generated in egcs will be passed to the 2.8.x releases for
+inclusion; the reverse is also taking place, though a bug fix may
+appear in one before it does in the other.
+
+@node egcs-robustness, , egcs-vs-2.8.0, egcs and 2.8.0
+@section How solid is egcs-1.0?
+
+While the 'e' stands for 'experimental', egcs has been tested thoroughly
+and should be of high quality. There are a few glitches which should be
+fixed shortly (in a 1.0.1 release, probably in early January):
+
+@itemize @bullet
+@item
+Deeply nested templates sometimes lead to a very large memory requirement
+if the @code{-Wreturn-type} option is on (note: this flag is implicitly
+turned on by @code{-W} or @code{-Wall}. A workaround is to give the
+flag @code{-Wno-return-type} if you use @code{-Wall}.
+
+@item
+On Red Hat 5.0, it may be necessary to link all C++ programs with
+@code{-lpthread} to work around an undefined symbol problem.
+
+@item
+A patch is needed to fix egcs on Solaris/X86. It is in the egcs FAQ
+(see above).
+@end itemize
+
+@node installation, evolution, egcs and 2.8.0, Top
@chapter Installation Issues and Problems
@menu
the debug symbol table considerably. The 2.7 version adds some symbol
table compression for ELF and Solaris targets.
+Users of egcs or 2.8.0 (when released) on ELF systems should definitely
+use GNU ld (2.8 or later), as it will automatically remove duplicate
+instantiations of templates, virtual function tables, or ``outlined''
+copies of inline functions.
+
@cindex collect linker, advantages
Advantages of collect:
@menu
* version 2.7.x:: What's changed in 2.7.x from earlier versions
-* libstdc++:: The GNU C++ standard library
-* new work:: What's been done since 2.7.x
-* egcs:: The Experimental GNU Compiler System
-* When?:: When can I get all this new stuff?
+* libstdc++::
@end menu
@node version 2.7.x, libstdc++, evolution, evolution
@end itemize
-@node libstdc++, new work, version 2.7.x, evolution
+@node libstdc++, , version 2.7.x, evolution
@section The GNU Standard C++ Library
The GNU Standard C++ Library (also called the ``GNU ANSI C++ Library''
in favor of enhancing libstdc++ to cover the full language, so while libg++
will always be available, enhancements to it should not be expected.
-@node new work, egcs, libstdc++, evolution
-@section What can we expect in future gcc releases?
-
-A great deal of work has gone into enhancements to the C++ front end, as well
-as to other aspects of the compiler.
-
-The next major release(s) of gcc/g++ can be expected to have the following
-features:
-
-@itemize @bullet
-@cindex new template implementation
-@item
-A completely new template implementation, much closer to the draft
-standard. Limitations in 2.7.2.x concerning inlining template functions
-will be eliminated. Static template data members, template class member
-functions, partial specification, and default template arguments will be
-supported. An instantiation method resembling that used in Borland C++
-(instantiating functions possibly in multiple .o files and using weak
-symbols to link correctly) will be provided, in addition to other
-options. The SGI version of STL will be shipped with libstdc++ and will
-compile unchanged.
-
-@item
-@cindex new exception implementation
-Exception handling has been re-worked; exceptions will work together
-with optimization.
-Actually, there are two separate implementations: one based on setjmp/longjmp
-and designed to be highly portable, and one designed to be more efficient but
-requiring more processor-specific support (getting exceptions right has proven
-to be extremely difficult and has been the chief obstacle to getting a new
-release out).
-
-@item
-@cindex RTTI
-RTTI has been re-done to work correctly and is on by default.
-
-@item
-@cindex overloading
-Overloading has been re-worked to conform to the latest draft of the
-standard.
-@end itemize
-
-Features that are still missing include namespaces and templates as
-template arguments.
-
-@node egcs, When?, new work, evolution
-@section What's this I hear about egcs?
-
-The egcs effort is a new effort to merge several threads of gcc
-development and to provide a faster development process.
-For more information see @file{http://www.cygnus.com/egcs/}.
-
-@node When?, , egcs, evolution
-@section OK, when can I get this stuff?
-
-The FSF has a policy of never announcing release dates in advance.
-I'm sure this is frustrating to a lot of people, since it's taken
-so long, and this frustration was one of the reasons the egcs effort
-was created. An egcs release should be expected to occur in the
-very near future. [ More on this next time ].
-
@node User Problems, legalities, evolution, Top
@chapter User Problems
implementation.
@item
While there is no libg++-specific document describing the STL
-implementation, SGI's web site, at @file{http://www.sgi.com/Technology/STL/},
-is an excellent resource.
+implementation, SGI's web site, at
+@file{http://www.sgi.com/Technology/STL/}, is an excellent resource.
+Note that the SGI version of STL is the one that is included with the
+egcs and 2.8.0 (when it occurs) releases of g++.
+
@end itemize
@node templates, undefined templates, documentation, User Problems
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