update
From-SVN: r17110
This commit is contained in:
Jason Merrill
parent
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@ -3,7 +3,7 @@
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@setfilename g++FAQ.info
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@settitle Frequently asked questions about the GNU C++ compiler
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@setchapternewpage off
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@c version: @(#)g++FAQ.texi 1.56 09/15/97
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@c version: @(#)g++FAQ.texi 1.57 12/14/97
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@c %**end of header
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@iftex
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@ -12,7 +12,7 @@
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@titlepage
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@title G++ FAQ
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@subtitle Frequently asked questions about the GNU C++ compiler
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@subtitle September 14, 1997
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@subtitle December 14, 1997
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@sp 1
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@author Joe Buck
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@page
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@ -35,15 +35,14 @@ all those who sent suggestions for improvements. Thanks to Marcus Speh
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for doing the index. A hypertext version is available on the World Wide
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Web at @file{http://www.cygnus.com/misc/g++FAQ_toc.html}.
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This document has just been reorganized a bit. There is some new
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information about upcoming g++ releases and egcs; more needs to be done
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but that will need to wait for next time. A diff would look misleadingly
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large, since I blew away and rebuilt the texinfo menus.
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@strong{News flash}: egcs has been released, and the 2.8.0 release is
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expected very soon!
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Please send updates and corrections to the FAQ to
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@code{jbuck@@synopsys.com}. Please do @emph{not} use me as a resource
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to get your questions answered; that's what @file{gnu.g++.help} is for and I
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don't have the time to support the net's use of g++.
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don't have the time to support the net's use of g++. If you ignore this
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request your message to me may be deleted without a reply. Sorry.
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Many FAQs, including this one, are available on the archive site
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``rtfm.mit.edu''; see @*
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@ -64,6 +63,7 @@ or in HTML form at @file{http://www.cerfnet.com/~mpcline/On-Line-C++-FAQs/}.
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@menu
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* basics:: What is g++? How do I get it?
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* egcs and 2.8.0:: The next generation(s) of g++
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* installation:: How to install, installation problems
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* evolution:: The Evolution of g++
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* User Problems:: Commonly reported problems and bugs
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@ -81,6 +81,14 @@ The basics: what is g++?
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* g++ for other platforms::
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* 1.x vs 2.x versions::
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The Next Generation(s) of g++
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* egcs-intro:: What is egcs?
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* egcs-whats-new:: What's new in egcs vs 2.7.2?
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* egcs-run-both:: How can I run both egcs and an FSF release?
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* egcs-vs-2.8.0:: How will egcs affect 2.8.0?
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* egcs-robustness:: How robust is egcs-1.0?
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Installation Issues and Problems
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* gcc-2 + g++-1::
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@ -102,11 +110,8 @@ Installation Issues and Problems
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The Evolution of g++
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* version 2.7.x::
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* version 2.7.x:: What's changed in 2.7.x from earlier versions
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* libstdc++::
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* new work::
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* egcs::
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* When?::
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User Problems
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@ -138,7 +143,7 @@ User Problems
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* assignment to streams::
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@end menu
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@node basics, installation, Top, Top
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@node basics, egcs and 2.8.0, Top, Top
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@chapter The basics: what is g++?
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@cindex Free Software Foundation
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@ -167,6 +172,11 @@ or GPL (@pxref{legalities}).
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@node latest versions, g++ for Unix, basics, basics
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@section What is the latest version of gcc, g++, and libg++?
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@cindex egcs release
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The egcs project (on the Web: @file{http://www.cygnus.com/egcs/}) has
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now released egcs-1.0 as of December 3, 1997.
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@cindex gcc/g++, version date
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The current version of gcc/g++ is 2.7.2.3, released August 20, 1997.
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Although that looks very recent, the only change is a minor patch to
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@ -436,7 +446,144 @@ install the C++ compiler as well.
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One could argue that we shouldn't even refer to "g++-2.x.y" but it's a
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convention. It means ``the C++ compiler included with gcc-2.x.y.''
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@node installation, evolution, basics, Top
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@node egcs and 2.8.0, installation, basics, Top
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@chapter The Next Generation(s) of g++
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@menu
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* egcs-intro:: What is egcs?
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* egcs-whats-new:: What's new in egcs vs 2.7.2?
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* egcs-run-both:: How can I run both egcs and an FSF release?
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* egcs-vs-2.8.0:: How will egcs affect 2.8.0?
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* egcs-robustness:: How robust is egcs-1.0?
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@end menu
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@node egcs-intro, egcs-whats-new, egcs and 2.8.0, egcs and 2.8.0
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@section What is egcs?
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egcs is the Experimental GNU compiler system (see
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@file{http://www.cygnus.com/egcs} on the Web). It is an effort to
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accelerate development of new gcc features by providing a more open
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development model than gcc has traditionally used.
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The first egcs release, egcs-1.0, came out on December 3, 1997.
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Questions not addressed here may be answered in the egcs FAQ
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(@file{http://www.cygnus.com/egcs/faq.html}).
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@node egcs-whats-new, egcs-run-both, egcs-intro, egcs and 2.8.0
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@section What new C++ features are in egcs?
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@strong{Note}: unless indicated otherwise, these features are expected
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to be present in g++ 2.8.0 when released.
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@itemize @bullet
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@item
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@cindex integrated libstdc++
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The standard C++ classes are integrated with the egcs release (this is
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@emph{not} expected to be true of gcc-2.8.0). libg++ is not being
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supported, though a version that will work with egcs has been
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contributed (FIXME: pointer?). The compiler and library are configured
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and built in one step.
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@item
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@cindex new template implementation
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A completely new template implementation, much closer to the draft
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standard. Limitations in 2.7.2.x concerning inlining template functions
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will be eliminated. Static template data members, template class member
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functions, partial specification, and default template arguments will be
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supported. An instantiation method resembling that used in Borland C++
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(instantiating functions possibly in multiple .o files and using weak
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symbols to link correctly) is provided, in addition to other
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options. The SGI version of STL is shipped verbatim with libstdc++.
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@item
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@cindex redundant template elimination
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@cindex templates: removing redundancy
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On ELF platforms (Linux/ELF, Solaris, SVR4), if the GNU linker is used,
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duplicated template functions and virtual function tables are eliminated
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at link time.
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@item
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@cindex repository
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@cindex -frepo
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The @code{-frepo} flag is supported in egcs (it will not be in 2.8.0).
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However, because of the previous item, I don't recommend its use on ELF
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systems.
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@item
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@cindex new exception implementation
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Exception handling has been re-worked; exceptions will work together
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with optimization.
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Actually, there are two separate implementations: one based on setjmp/longjmp
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and designed to be highly portable, and one designed to be more efficient but
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requiring more processor-specific support (getting exceptions right has proven
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to be extremely difficult and has been the chief obstacle to getting a new
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release out).
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@item
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@cindex RTTI
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RTTI has been re-done to work correctly and is on by default.
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@item
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@cindex overloading
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Overloading has been re-worked to conform to the latest draft of the
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standard.
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@item
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There are many more changes: see @file{http://www.cygnus.com/egcs/c++features.html} for a list.
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@end itemize
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Features that are still missing include namespaces and templates as
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template arguments.
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@node egcs-run-both, egcs-vs-2.8.0, egcs-whats-new, egcs and 2.8.0
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@section How can I run both egcs and an FSF release of g++ on the same machine?
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The recommended approach is to provide a different argument to the
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@code{--prefix} flag when you configure egcs. For example, say
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@code{--prefix=/usr/local/egcs} and then, after installation, you
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can make symbolic links from @file{/usr/local/egcs/bin} to whereever
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you want, for example
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@example
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ln -s /usr/local/egcs/bin/gcc /usr/local/bin/egcc
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ln -s /usr/local/egcs/bin/g++ /usr/local/bin/eg++
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@end example
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@node egcs-vs-2.8.0, egcs-robustness, egcs-run-both, egcs and 2.8.0
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@section What about 2.8.0? How does egcs affect the 2.8.x development?
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2.8.0 is expected Real Soon Now (I would guess by the end of 1997, but that
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is only a guess). The C++ front end should be essentially the same.
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Bug fixes generated in egcs will be passed to the 2.8.x releases for
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inclusion; the reverse is also taking place, though a bug fix may
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appear in one before it does in the other.
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@node egcs-robustness, , egcs-vs-2.8.0, egcs and 2.8.0
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@section How solid is egcs-1.0?
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While the 'e' stands for 'experimental', egcs has been tested thoroughly
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and should be of high quality. There are a few glitches which should be
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fixed shortly (in a 1.0.1 release, probably in early January):
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@itemize @bullet
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@item
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Deeply nested templates sometimes lead to a very large memory requirement
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if the @code{-Wreturn-type} option is on (note: this flag is implicitly
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turned on by @code{-W} or @code{-Wall}. A workaround is to give the
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flag @code{-Wno-return-type} if you use @code{-Wall}.
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@item
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On Red Hat 5.0, it may be necessary to link all C++ programs with
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@code{-lpthread} to work around an undefined symbol problem.
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@item
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A patch is needed to fix egcs on Solaris/X86. It is in the egcs FAQ
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(see above).
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@end itemize
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@node installation, evolution, egcs and 2.8.0, Top
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@chapter Installation Issues and Problems
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@menu
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@ -554,6 +701,11 @@ debug format (e.g. Suns running SunOS 4.x), the GNU linker compresses
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the debug symbol table considerably. The 2.7 version adds some symbol
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table compression for ELF and Solaris targets.
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Users of egcs or 2.8.0 (when released) on ELF systems should definitely
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use GNU ld (2.8 or later), as it will automatically remove duplicate
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instantiations of templates, virtual function tables, or ``outlined''
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copies of inline functions.
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@cindex collect linker, advantages
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Advantages of collect:
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@ -951,10 +1103,7 @@ in the future.
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@menu
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* version 2.7.x:: What's changed in 2.7.x from earlier versions
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* libstdc++:: The GNU C++ standard library
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* new work:: What's been done since 2.7.x
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* egcs:: The Experimental GNU Compiler System
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* When?:: When can I get all this new stuff?
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* libstdc++::
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@end menu
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@node version 2.7.x, libstdc++, evolution, evolution
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@ -1086,7 +1235,7 @@ though they are not needed).
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@end itemize
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@node libstdc++, new work, version 2.7.x, evolution
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@node libstdc++, , version 2.7.x, evolution
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@section The GNU Standard C++ Library
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The GNU Standard C++ Library (also called the ``GNU ANSI C++ Library''
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@ -1112,67 +1261,6 @@ The maintainers of libg++ have de-emphasized work on the older libg++ classes
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in favor of enhancing libstdc++ to cover the full language, so while libg++
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will always be available, enhancements to it should not be expected.
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@node new work, egcs, libstdc++, evolution
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@section What can we expect in future gcc releases?
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A great deal of work has gone into enhancements to the C++ front end, as well
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as to other aspects of the compiler.
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The next major release(s) of gcc/g++ can be expected to have the following
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features:
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@itemize @bullet
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@cindex new template implementation
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@item
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A completely new template implementation, much closer to the draft
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standard. Limitations in 2.7.2.x concerning inlining template functions
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will be eliminated. Static template data members, template class member
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functions, partial specification, and default template arguments will be
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supported. An instantiation method resembling that used in Borland C++
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(instantiating functions possibly in multiple .o files and using weak
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symbols to link correctly) will be provided, in addition to other
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options. The SGI version of STL will be shipped with libstdc++ and will
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compile unchanged.
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@item
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@cindex new exception implementation
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Exception handling has been re-worked; exceptions will work together
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with optimization.
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Actually, there are two separate implementations: one based on setjmp/longjmp
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and designed to be highly portable, and one designed to be more efficient but
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requiring more processor-specific support (getting exceptions right has proven
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to be extremely difficult and has been the chief obstacle to getting a new
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release out).
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@item
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@cindex RTTI
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RTTI has been re-done to work correctly and is on by default.
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@item
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@cindex overloading
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Overloading has been re-worked to conform to the latest draft of the
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standard.
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@end itemize
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Features that are still missing include namespaces and templates as
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template arguments.
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@node egcs, When?, new work, evolution
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@section What's this I hear about egcs?
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The egcs effort is a new effort to merge several threads of gcc
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development and to provide a faster development process.
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For more information see @file{http://www.cygnus.com/egcs/}.
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@node When?, , egcs, evolution
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@section OK, when can I get this stuff?
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The FSF has a policy of never announcing release dates in advance.
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I'm sure this is frustrating to a lot of people, since it's taken
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so long, and this frustration was one of the reasons the egcs effort
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was created. An egcs release should be expected to occur in the
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very near future. [ More on this next time ].
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@node User Problems, legalities, evolution, Top
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@chapter User Problems
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@ -1620,8 +1708,11 @@ another manual @file{libio/iostream.texi} describing the iostreams
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implementation.
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@item
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While there is no libg++-specific document describing the STL
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implementation, SGI's web site, at @file{http://www.sgi.com/Technology/STL/},
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is an excellent resource.
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implementation, SGI's web site, at
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@file{http://www.sgi.com/Technology/STL/}, is an excellent resource.
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Note that the SGI version of STL is the one that is included with the
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egcs and 2.8.0 (when it occurs) releases of g++.
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@end itemize
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@node templates, undefined templates, documentation, User Problems
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