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14fe7b530d
The next log entry shows the actual changes by Paul Eggert. Fix a problem with aliasing and vector headers. GCC 4.6.0 optimizes based on type-based alias analysis. For example, if b is of type struct buffer * and v of type struct Lisp_Vector *, then gcc -O2 was incorrectly assuming that &b->size != &v->size, and therefore "v->size = 1; b->size = 2; return v->size;" must therefore return 1. This assumption is incorrect for Emacs, since it type-puns struct Lisp_Vector * with many other types. To fix this problem, this patch adds a new type struct vector_header that documents the constraints on layout of vectors and pseudovectors, and helps optimizing compilers not get fooled by Emacs's type punning. It also adds the macros XSETTYPED_PVECTYPE XSETTYPED_PSEUDOVECTOR, TYPED_PSEUDOVECTORP, for similar reasons. src/lisp.h (XVECTOR_SIZE): New convenience macro. All previous uses of XVECTOR (foo)->size replaced to use this macro, to avoid the hassle of writing XVECTOR (foo)->header.size. src/lisp.h: Say "vectorlike header" rather than "vector header. (struct vectorlike_header): Rename from struct vector_header. (XVECTORLIKE_HEADER_SIZE): Renamed from XVECTOR_HEADER_SIZE. All uses changed. (XVECTOR_HEADER_SIZE): New macro, for use in XSETPSEUDOVECTOR. (XSETTYPED_PVECTYPE): New macro, specifying the name of the size member. (XSETPVECTYPE): Rewrite in terms of new macro. (XSETPVECTYPESIZE): New macro, specifying both type and size. This is a bit clearer, and further avoids the possibility of undesirable aliasing. (XSETTYPED_PSEUDOVECTOR): New macro, specifying the size. (XSETPSEUDOVECTOR): Rewrite in terms of XSETTYPED_PSEUDOVECTOR and XVECTOR_HEADER_SIZE. (XSETSUBR): Rewrite in terms of XSETTYPED_PSEUDOVECTOR and XSIZE, since Lisp_Subr is a special case (no "next" field). (ASIZE): Rewrite in terms of XVECTOR_SIZE. (struct vector_header): New type. (TYPED_PSEUDOVECTORP): New macro, also specifying the C type of the object, to help avoid aliasing. (PSEUDOVECTORP): Rewrite in terms of TYPED_PSEUDOVECTORP. (SUBRP): Likewise, since Lisp_Subr is a special case. src/lisp.h (struct Lisp_Vector, struct Lisp_Char_Table): (struct Lisp_Sub_Char_Table, struct Lisp_Bool_Vector): (struct Lisp_Hash_Table): Combine first two members into a single struct vector_header member. All uses of "size" and "next" members changed to be "header.size" and "header.next". src/buffer.h (struct buffer): Likewise. src/font.h (struct font_spec, struct font_entity, struct font): Likewise. src/frame.h (struct frame): Likewise. src/process.h (struct Lisp_Process): Likewise. src/termhooks.h (struct terminal): Likewise. src/window.c (struct save_window_data, struct saved_window): Likewise. src/window.h (struct window): Likewise. src/alloc.c (allocate_buffer, Fmake_bool_vector, allocate_pseudovector): Use XSETPVECTYPESIZE, not XSETPVECTYPE, to avoid aliasing problems. src/buffer.c (init_buffer_once): Likewise. src/lread.c (defsubr): Use XSETTYPED_PVECTYPE, since Lisp_Subr is a special case. src/process.c (Fformat_network_address): Use local var for size, for brevity. src/fns.c (vector): Remove; this old hack is no longer needed. src/bytecode.c (exec_byte_code): Don't use XVECTOR before CHECK_VECTOR. |
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Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
2010, 2011 Free Software Foundation, Inc.
See the end of the file for license conditions.
This directory tree holds version 23.3.50 of GNU Emacs, the extensible,
customizable, self-documenting real-time display editor.
The file INSTALL in this directory says how to build and install GNU
Emacs on various systems, once you have unpacked or checked out the
entire Emacs file tree.
See the file etc/NEWS for information on new features and other
user-visible changes in recent versions of Emacs.
The file etc/PROBLEMS contains information on many common problems that
occur in building, installing and running Emacs.
You may encounter bugs in this release. If you do, please report
them; your bug reports are valuable contributions to the FSF, since
they allow us to notice and fix problems on machines we don't have, or
in code we don't use often. Please send bug reports to the mailing
list bug-gnu-emacs@gnu.org. If possible, use M-x report-emacs-bug.
See the "Bugs" section of the Emacs manual for more information on how
to report bugs. (The file `BUGS' in this directory explains how you
can find and read that section using the Info files that come with
Emacs.) See `etc/MAILINGLISTS' for more information on mailing lists
relating to GNU packages.
The `etc' subdirectory contains several other files, named in capital
letters, which you might consider looking at when installing GNU
Emacs.
The file `configure' is a shell script to acclimate Emacs to the
oddities of your processor and operating system. It creates the file
`Makefile' (a script for the `make' program), which automates the
process of building and installing Emacs. See INSTALL for more
detailed information.
The file `configure.in' is the input used by the autoconf program to
construct the `configure' script. Since Emacs has some configuration
requirements that autoconf can't meet directly, and for historical
reasons, `configure.in' uses an unholy marriage of custom-baked
configuration code and autoconf macros. If you want to rebuild
`configure' from `configure.in', you will need to install a recent
version of autoconf and GNU m4.
The file `Makefile.in' is a template used by `configure' to create
`Makefile'.
The file `make-dist' is a shell script to build a distribution tar
file from the current Emacs tree, containing only those files
appropriate for distribution. If you make extensive changes to Emacs,
this script will help you distribute your version to others.
There are several subdirectories:
`src' holds the C code for Emacs (the Emacs Lisp interpreter and
its primitives, the redisplay code, and some basic editing
functions).
`lisp' holds the Emacs Lisp code for Emacs (most everything else).
`leim' holds the library of Emacs input methods, Lisp code and
auxiliary data files required to type international characters
which can't be directly produced by your keyboard.
`lib-src' holds the source code for some utility programs for use by or
with Emacs, like movemail and etags.
`etc' holds miscellaneous architecture-independent data files Emacs
uses, like the tutorial text and tool bar images.
The contents of the `lisp', `leim', `info', and `doc'
subdirectories are architecture-independent too.
`info' holds the Info documentation tree for Emacs.
`doc/emacs' holds the source code for the Emacs Manual. If you modify the
manual sources, you will need the `makeinfo' program to produce
an updated manual. `makeinfo' is part of the GNU Texinfo
package; you need a suitably recent version of Texinfo.
`doc/lispref' holds the source code for the Emacs Lisp reference manual.
`doc/lispintro' holds the source code for the Introduction to Programming
in Emacs Lisp manual.
`msdos' holds configuration files for compiling Emacs under MSDOG.
`nextstep' holds instructions and some other files for compiling the
Nextstep port of Emacs, for GNUstep and Mac OS X Cocoa.
`nt' holds various command files and documentation files that pertain
to building and running Emacs on Windows 9X/ME/NT/2000/XP.
`test' holds tests for various aspects of Emacs's functionality.
Building Emacs on non-Posix platforms requires tools that aren't part
of the standard distribution of the OS. The platform-specific README
files and installation instructions should list the required tools.
This file is part of GNU Emacs.
GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.