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index.html (5.8): New entry on ABIs.

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2001-11-07  Nathan Myers  <ncm@cantrip.org>

	* docs/html/faq/index.html (5.8):  New entry on ABIs.
	* docs/html/faq/index.txt:  Regenerate.

From-SVN: r46836
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Nathan Myers 2001-11-07 21:08:53 +00:00 committed by Phil Edwards
parent 83c6af9942
commit 2dac8f87e8
3 changed files with 195 additions and 93 deletions
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5
libstdc++-v3/ChangeLog
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@ -1,3 +1,8 @@
2001-11-07 Nathan Myers <ncm@cantrip.org>
* docs/html/faq/index.html (5.8): New entry on ABIs.
* docs/html/faq/index.txt: Regenerate.
2001-11-07 Phil Edwards <pme@gcc.gnu.org>
* docs/html/faq/index.html: Explain libsupc++, mention 'long long'

48
libstdc++-v3/docs/html/faq/index.html
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@ -87,6 +87,7 @@ http://gcc.gnu.org/onlinedocs/libstdc++/faq/</a>.</p>
<li><a href="#5_5">[removed]</a>
<li><a href="#5_6">Is libstdc++-v3 thread-safe?</a>
<li><a href="#5_7">How do I get a copy of the ISO C++ Standard?</a>
<li><a href="#5_8">What's an ABI and why is it so messy?</a>
</ol>
</ol>
@ -810,6 +811,53 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff
<a href="http://www.iso.ch/">ISO homepage</a> and find out!
</p>
<hr>
<h2><a name="5_8">5.8 What's an ABI and why is it so messy?</a></h2>
<p>&quot;ABI&quot; stands for &quot;Application Binary Interface.&quot;
Conventionally, it refers to a great mass of details about how
arguments are arranged on the call stack and/or in registers, and
how various types are arranged and padded in structs. A single CPU
design may suffer multiple ABIs designed by different development
tool vendors who made different choices, or even by the same vendor
for different target applications or compiler versions. In ideal
circumstances the CPU designer presents one ABI and all the OSes and
compilers use it. In practice every ABI omits details that compiler
implementers (consciously or accidentally) must choose for themselves.
</p>
<p>That ABI definition suffices for compilers to generate code so a
program can interact safely with an OS and its lowest-level libraries.
Users usually want an ABI to encompass more detail, allowing libraries
built with different compilers (or different releases of the same
compiler!) to be linked together. For C++, this includes many more
details than for C, and CPU designers (for good reasons elaborated
below) have not stepped up to publish C++ ABIs. The details include
virtual function implementation, struct inheritance layout, name
mangling, and exception handling. Such an ABI has been defined for
GNU C++, and is immediately useful for embedded work relying only on
a &quot;free-standing implementation&quot; that doesn't include (much
of) the standard library. It is a good basis for the work to come.
</p>
<p>A useful C++ ABI must also incorporate many details of the standard
library implementation. For a C ABI, the layouts of a few structs
(such as FILE, stat, jmpbuf, and the like) and a few macros suffice.
For C++, the details include the complete set of names of functions
and types used, the offsets of class members and virtual functions,
and the actual definitions of all inlines. C++ exposes many more
library details to the caller than C does. It makes defining
a complete ABI a much bigger undertaking, and requires not just
documenting library implementation details, but carefully designing
those details so that future bug fixes and optimizations don't
force breaking the ABI.
</p>
<p>There are ways to help isolate library implementation details from the
ABI, but they trade off against speed. Library details used in
inner loops (e.g., getchar) must be exposed and frozen for all
time, but many others may reasonably be kept hidden from user code,
so they may later be changed. Deciding which, and implementing
the decisions, must happen before you can reasonably document a
candidate C++ ABI that encompasses the standard library.
</p>
<!-- ####################################################### -->
<hr>

235
libstdc++-v3/docs/html/faq/index.txt
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@ -52,6 +52,7 @@
5. [41][removed]
6. [42]Is libstdc++-v3 thread-safe?
7. [43]How do I get a copy of the ISO C++ Standard?
8. [44]What's an ABI and why is it so messy?
_________________________________________________________________
1.0 General Information
@ -62,13 +63,13 @@
project to implement the ISO 14882 Standard C++ library as described
in chapters 17 through 27 and annex D. As the library reaches stable
plateaus, it is captured in a snapshot and released. The current
release is [44]the eleventh snapshot. For those who want to see
release is [45]the eleventh snapshot. For those who want to see
exactly how far the project has come, or just want the latest
bleeding-edge code, the up-to-date source is available over anonymous
CVS, and can even be browsed over the Web (see below).
A more formal description of the V3 goals can be found in the official
[45]design document.
[46]design document.
_________________________________________________________________
1.2 Why should I use libstdc++?
@ -81,8 +82,8 @@
The GNU C/C++/FORTRAN/<pick-a-language> compiler (gcc, g++, etc) is
widely considered to be one of the leading compilers in the world. Its
development has recently been taken over by the [46]GCC team. All of
the rapid development and near-legendary [47]portability that are the
development has recently been taken over by the [47]GCC team. All of
the rapid development and near-legendary [48]portability that are the
hallmarks of an open-source project are being applied to libstdc++.
That means that all of the Standard classes and functions (such as
@ -100,16 +101,16 @@
Development and discussion is held on the libstdc++ mailing list.
Subscribing to the list, or searching the list archives, is open to
everyone. You can read instructions for doing so on the [48]homepage.
everyone. You can read instructions for doing so on the [49]homepage.
If you have questions, ideas, code, or are just curious, sign up!
_________________________________________________________________
1.4 How do I get libstdc++?
The eleventh (and latest) snapshot of libstdc++-v3 is [49]available
The eleventh (and latest) snapshot of libstdc++-v3 is [50]available
via ftp. The filename is libstdc++-2.92.tar.gz.
The [50]homepage has instructions for retrieving the latest CVS
The [51]homepage has instructions for retrieving the latest CVS
sources, and for browsing the CVS sources over the web.
The subset commonly known as the Standard Template Library (chapters
@ -125,7 +126,7 @@
1.6 How do I contribute to the effort?
Here is [51]a page devoted to this topic. Subscribing to the mailing
Here is [52]a page devoted to this topic. Subscribing to the mailing
list (see above, or the homepage) is a very good idea if you have
something to contribute, or if you have spare time and want to help.
Contributions don't have to be in the form of source code; anybody who
@ -160,11 +161,11 @@
extracted into an updated utilities library, but nobody has stated
such a project yet.
(The [52]Boost site houses free C++ libraries that do varying things,
(The [53]Boost site houses free C++ libraries that do varying things,
and happened to be started by members of the Standards Committee.
Certain "useful stuff" classes will probably migrate there.)
For the bold and/or desperate, the [53]GCC FAQ describes where to find
For the bold and/or desperate, the [54]GCC FAQ describes where to find
the last libg++ source.
_________________________________________________________________
@ -174,16 +175,16 @@
remains unanswered, then just ask the mailing list. At present, you do
not need to be subscribed to the list to send a message to it. More
information is available on the homepage (including how to browse the
list archives); to send to the list, use [54]libstdc++@gcc.gnu.org.
list archives); to send to the list, use [55]libstdc++@gcc.gnu.org.
If you have a question that you think should be included here, or if
you have a question about a question/answer here, contact [55]Phil
Edwards or [56]Gabriel Dos Reis.
you have a question about a question/answer here, contact [56]Phil
Edwards or [57]Gabriel Dos Reis.
_________________________________________________________________
1.9 What are the license terms for libstdc++-v3?
See [57]our license description for these and related questions.
See [58]our license description for these and related questions.
_________________________________________________________________
2.0 Installation
@ -200,13 +201,13 @@
* The GNU Autotools are needed if you are messing with the configury
or makefiles.
The file [58]documentation.html provides a good overview of the steps
The file [59]documentation.html provides a good overview of the steps
necessary to build, install, and use the library. Instructions for
configuring the library with new flags such as --enable-threads are
there also, as well as patches and instructions for working with GCC
2.95.
The top-level install.html and [59]RELEASE-NOTES files contain the
The top-level install.html and [60]RELEASE-NOTES files contain the
exact build and installation instructions. You may wish to browse
those files over CVSweb ahead of time to get a feel for what's
required. RELEASE-NOTES is located in the ".../docs/17_intro/"
@ -223,8 +224,8 @@
The Concurrent Versions System is one of several revision control
packages. It was selected for GNU projects because it's free (speech),
free (beer), and very high quality. The [60]CVS entry in the GNU
software catalogue has a better description as well as a [61]link to
free (beer), and very high quality. The [61]CVS entry in the GNU
software catalogue has a better description as well as a [62]link to
the makers of CVS.
The "anonymous client checkout" feature of CVS is similar to anonymous
@ -275,7 +276,7 @@
people don't like it, so here are two pseudo-solutions:
If the only functions from libstdc++.a which you need are language
support functions (those listed in [62]clause 18 of the standard,
support functions (those listed in [63]clause 18 of the standard,
e.g., new and delete), then try linking against libsupc++.a (usually
specifying -lsupc++ when calling g++ for the final link step will do
it). This library contains only those support routines, one per object
@ -331,7 +332,7 @@
install GNU as and arrange for the GCC build to use it (or merge the
sources and build it during the bootstrap).
Anyone who [63]knows the DEC assembler well enough to provide the
Anyone who [64]knows the DEC assembler well enough to provide the
equivalent of these two pseudos would win praise and accolades from
many.
_________________________________________________________________
@ -359,7 +360,7 @@
include/Makefile, resulting in files like gthr.h and gthr-single.h not
being found.
Please read [64]the configuration instructions for GCC, specifically
Please read [65]the configuration instructions for GCC, specifically
the part about configuring in a separate build directory, and how
strongly recommended it is. Building in the source directory is
fragile, is rarely tested, and tends to break, as in this case. This
@ -411,17 +412,17 @@ New:
4.3 Bugs in the C++ language/lib specification
Yes, unfortunately, there are some. In a [65]message to the list,
Yes, unfortunately, there are some. In a [66]message to the list,
Nathan Myers announced that he has started a list of problems in the
ISO C++ Standard itself, especially with regard to the chapters that
concern the library. The list itself is [66]posted on his website.
concern the library. The list itself is [67]posted on his website.
Developers who are having problems interpreting the Standard may wish
to consult his notes.
For those people who are not part of the ISO Library Group (i.e.,
nearly all of us needing to read this page in the first place :-), a
public list of the library defects is occasionally published [67]here.
Some of these have resulted in [68]code changes.
public list of the library defects is occasionally published [68]here.
Some of these have resulted in [69]code changes.
_________________________________________________________________
4.4 Things in libstdc++ that look like bugs
@ -454,7 +455,7 @@ New:
state on the previous file. The reason is that the state flags are not
cleared on a successful call to open(). The standard unfortunately did
not specify behavior in this case, and to everybody's great sorrow,
the [69]proposed LWG resolution (see DR #22) is to leave the flags
the [70]proposed LWG resolution (see DR #22) is to leave the flags
unchanged. You must insert a call to fs.clear() between the calls to
close() and open(), and then everything will work like we all expect
it to work.
@ -464,14 +465,14 @@ New:
same namespace as other comparison functions (e.g., 'using' them and
the <iterator> header), then you will suddenly be faced with huge
numbers of ambiguity errors. This was discussed on the -v3 list;
Nathan Myers [70]sums things up here.
Nathan Myers [71]sums things up here.
The g++-3 headers are not ours
If you have found an extremely broken header file which is causing
problems for you, look carefully before submitting a "high" priority
bug report (which you probably shouldn't do anyhow; see the last
paragraph of the page describing [71]the GCC bug database).
paragraph of the page describing [72]the GCC bug database).
If the headers are in ${prefix}/include/g++-3, then you are using the
old libstdc++-v2 library, which is nonstandard and unmaintained. Do
@ -479,7 +480,7 @@ New:
Currently our header files are installed in ${prefix}/include/g++-v3
(see the 'v'?). This may change with the next release of GCC, as it
may be too confusing, but [72]the question has not yet been decided.
may be too confusing, but [73]the question has not yet been decided.
glibc If you're on a GNU/Linux system and have just upgraded to glibc
2.2, but are still using gcc 2.95.2, then you should have read the
@ -492,7 +493,7 @@ type has changed in glibc 2.2. The patch is at
http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff
Note that 2.95.x shipped with the [73]old v2 library which is no
Note that 2.95.x shipped with the [74]old v2 library which is no
longer maintained. Also note that gcc 2.95.3 fixes this problem, but
requires a separate patch for libstdc++-v3.
@ -505,23 +506,23 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff
visibility, or you just plain forgot, etc).
More information, including how to optionally enable/disable the
checks, is available [74]here.
checks, is available [75]here.
_________________________________________________________________
4.5 Aw, that's easy to fix!
If you have found a bug in the library and you think you have a
working fix, then send it in! The main GCC site has a page on
[75]submitting patches that covers the procedure, but for libstdc++
[76]submitting patches that covers the procedure, but for libstdc++
you should also send the patch to our mailing list in addition to the
GCC patches mailing list. The libstdc++ [76]contributors' page also
GCC patches mailing list. The libstdc++ [77]contributors' page also
talks about how to submit patches.
In addition to the description, the patch, and the ChangeLog entry, it
is a Good Thing if you can additionally create a small test program to
test for the presence of the bug that your patch fixes. Bugs have a
way of being reintroduced; if an old bug creeps back in, it will be
caught immediately by the [77]testsuite -- but only if such a test
caught immediately by the [78]testsuite -- but only if such a test
exists.
_________________________________________________________________
@ -555,7 +556,7 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff
libstdc++. Some of that is already happening, see 4.2. Some of
those changes are being predicted by the library maintainers, and
we add code to the library based on what the current proposed
resolution specifies. Those additions are listed in [78]the
resolution specifies. Those additions are listed in [79]the
extensions page.
2. Performance tuning. Lots of performance tuning. This too is
already underway for post-3.0 releases, starting with memory
@ -571,13 +572,13 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff
type from C99.) Bugfixes and rewrites (to improve or fix thread
safety, for instance) will of course be a continuing task.
[79]This question about the next libstdc++ prompted some brief but
interesting [80]speculation.
[80]This question about the next libstdc++ prompted some brief but
interesting [81]speculation.
_________________________________________________________________
5.3 What about the STL from SGI?
The [81]STL from SGI, version 3.3, was the most recent merge of the
The [82]STL from SGI, version 3.3, was the most recent merge of the
STL codebase. The code in libstdc++ contains many fixes and changes,
and it is very likely that the SGI code is no longer under active
development. We expect that no future merges will take place.
@ -598,7 +599,7 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff
#include <ext/hash_map>
Extensions to the library have [82]their own page.
Extensions to the library have [83]their own page.
_________________________________________________________________
5.5 [removed]
@ -646,8 +647,8 @@ a
both read and write access to objects; do not assume that two threads
may read a shared standard container at the same time.
See chapters [83]17 (library introduction), [84]23 (containers), and
[85]27 (I/O) for more information.
See chapters [84]17 (library introduction), [85]23 (containers), and
[86]27 (I/O) for more information.
_________________________________________________________________
5.7 How do I get a copy of the ISO C++ Standard?
@ -658,16 +659,63 @@ a
their two-meeting commitment for voting rights, may get a copy of the
standard from their respective national standards organization. In the
USA, this national standards organization is ANSI and their website is
right [86]here. (And if you've already registered with them, clicking
this link will take you to directly to the place where you can [87]buy
right [87]here. (And if you've already registered with them, clicking
this link will take you to directly to the place where you can [88]buy
the standard on-line.
Who is your country's member body? Visit the [88]ISO homepage and find
Who is your country's member body? Visit the [89]ISO homepage and find
out!
_________________________________________________________________
See [89]license.html for copying conditions. Comments and suggestions
are welcome, and may be sent to [90]the libstdc++ mailing list.
5.8 What's an ABI and why is it so messy?
"ABI" stands for "Application Binary Interface." Conventionally, it
refers to a great mass of details about how arguments are arranged on
the call stack and/or in registers, and how various types are arranged
and padded in structs. A single CPU design may suffer multiple ABIs
designed by different development tool vendors who made different
choices, or even by the same vendor for different target applications
or compiler versions. In ideal circumstances the CPU designer presents
one ABI and all the OSes and compilers use it. In practice every ABI
omits details that compiler implementers (consciously or accidentally)
must choose for themselves.
That ABI definition suffices for compilers to generate code so a
program can interact safely with an OS and its lowest-level libraries.
Users usually want an ABI to encompass more detail, allowing libraries
built with different compilers (or different releases of the same
compiler!) to be linked together. For C++, this includes many more
details than for C, and CPU designers (for good reasons elaborated
below) have not stepped up to publish C++ ABIs. The details include
virtual function implementation, struct inheritance layout, name
mangling, and exception handling. Such an ABI has been defined for GNU
C++, and is immediately useful for embedded work relying only on a
"free-standing implementation" that doesn't include (much of) the
standard library. It is a good basis for the work to come.
A useful C++ ABI must also incorporate many details of the standard
library implementation. For a C ABI, the layouts of a few structs
(such as FILE, stat, jmpbuf, and the like) and a few macros suffice.
For C++, the details include the complete set of names of functions
and types used, the offsets of class members and virtual functions,
and the actual definitions of all inlines. C++ exposes many more
library details to the caller than C does. It makes defining a
complete ABI a much bigger undertaking, and requires not just
documenting library implementation details, but carefully designing
those details so that future bug fixes and optimizations don't force
breaking the ABI.
There are ways to help isolate library implementation details from the
ABI, but they trade off against speed. Library details used in inner
loops (e.g., getchar) must be exposed and frozen for all time, but
many others may reasonably be kept hidden from user code, so they may
later be changed. Deciding which, and implementing the decisions, must
happen before you can reasonably document a candidate C++ ABI that
encompasses the standard library.
_________________________________________________________________
See [90]license.html for copying conditions. Comments and suggestions
are welcome, and may be sent to [91]the libstdc++ mailing list.
References
@ -714,50 +762,51 @@ References
41. ../faq/index.html#5_5
42. ../faq/index.html#5_6
43. ../faq/index.html#5_7
44. http://gcc.gnu.org/libstdc++/download.html
45. ../17_intro/DESIGN
46. http://gcc.gnu.org/
47. http://gcc.gnu.org/gcc-2.95/buildstat.html
48. http://gcc.gnu.org/libstdc++/
49. http://gcc.gnu.org/libstdc++/download.html
50. http://gcc.gnu.org/libstdc++/
51. ../17_intro/contribute.html
52. http://www.boost.org/
53. http://gcc.gnu.org/fom_serv/cache/33.html
54. mailto:libstdc++@gcc.gnu.org
55. mailto:pme@gcc.gnu.org
56. mailto:gdr@gcc.gnu.org
57. ../17_intro/license.html
58. ../documentation.html
59. ../17_intro/RELEASE-NOTES
60. http://www.gnu.org/software/cvs/cvs.html
61. http://www.cvshome.org/
62. ../18_support/howto.html
63. http://gcc.gnu.org/ml/libstdc++/2000-12/msg00279.html
64. http://gcc.gnu.org/install/configure.html
65. http://gcc.gnu.org/ml/libstdc++/1998/msg00006.html
66. http://www.cantrip.org/draft-bugs.txt
67. http://anubis.dkuug.dk/jtc1/sc22/wg21/
68. ../faq/index.html#5_2
69. ../ext/howto.html#5
70. http://gcc.gnu.org/ml/libstdc++/2001-01/msg00247.html
71. http://gcc.gnu.org/gnatswrite.html
72. http://gcc.gnu.org/ml/gcc/2000-10/msg00732.html
73. ../faq/index.html#4_4_interface
74. ../19_diagnostics/howto.html#3
75. http://gcc.gnu.org/contribute.html
76. ../17_intro/contribute.html
77. ../faq/index.html#2_4
78. ../ext/howto.html#5
79. http://gcc.gnu.org/ml/libstdc++/1999/msg00080.html
80. http://gcc.gnu.org/ml/libstdc++/1999/msg00084.html
81. http://www.sgi.com/Technology/STL/
82. ../ext/howto.html
83. ../17_intro/howto.html#3
84. ../23_containers/howto.html#3
85. ../27_io/howto.html#9
86. http://www.ansi.org/
87. http://webstore.ansi.org/ansidocstore/product.asp?sku=ISO%2FIEC+14882%2D1998
88. http://www.iso.ch/
89. ../17_intro/license.html
90. mailto:libstdc++@gcc.gnu.org
44. ../faq/index.html#5_8
45. http://gcc.gnu.org/libstdc++/download.html
46. ../17_intro/DESIGN
47. http://gcc.gnu.org/
48. http://gcc.gnu.org/gcc-2.95/buildstat.html
49. http://gcc.gnu.org/libstdc++/
50. http://gcc.gnu.org/libstdc++/download.html
51. http://gcc.gnu.org/libstdc++/
52. ../17_intro/contribute.html
53. http://www.boost.org/
54. http://gcc.gnu.org/fom_serv/cache/33.html
55. mailto:libstdc++@gcc.gnu.org
56. mailto:pme@gcc.gnu.org
57. mailto:gdr@gcc.gnu.org
58. ../17_intro/license.html
59. ../documentation.html
60. ../17_intro/RELEASE-NOTES
61. http://www.gnu.org/software/cvs/cvs.html
62. http://www.cvshome.org/
63. ../18_support/howto.html
64. http://gcc.gnu.org/ml/libstdc++/2000-12/msg00279.html
65. http://gcc.gnu.org/install/configure.html
66. http://gcc.gnu.org/ml/libstdc++/1998/msg00006.html
67. http://www.cantrip.org/draft-bugs.txt
68. http://anubis.dkuug.dk/jtc1/sc22/wg21/
69. ../faq/index.html#5_2
70. ../ext/howto.html#5
71. http://gcc.gnu.org/ml/libstdc++/2001-01/msg00247.html
72. http://gcc.gnu.org/gnatswrite.html
73. http://gcc.gnu.org/ml/gcc/2000-10/msg00732.html
74. ../faq/index.html#4_4_interface
75. ../19_diagnostics/howto.html#3
76. http://gcc.gnu.org/contribute.html
77. ../17_intro/contribute.html
78. ../faq/index.html#2_4
79. ../ext/howto.html#5
80. http://gcc.gnu.org/ml/libstdc++/1999/msg00080.html
81. http://gcc.gnu.org/ml/libstdc++/1999/msg00084.html
82. http://www.sgi.com/Technology/STL/
83. ../ext/howto.html
84. ../17_intro/howto.html#3
85. ../23_containers/howto.html#3
86. ../27_io/howto.html#9
87. http://www.ansi.org/
88. http://webstore.ansi.org/ansidocstore/product.asp?sku=ISO%2FIEC+14882%2D1998
89. http://www.iso.ch/
90. ../17_intro/license.html
91. mailto:libstdc++@gcc.gnu.org