Prepare for radical source tree reorganization. zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

1 files changed, 539 insertions, 0 deletions

diff --git a/REORG.TODO/manual/maint.texi b/REORG.TODO/manual/maint.texi
new file mode 100644
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+++ b/REORG.TODO/manual/maint.texi
@@ -0,0 +1,539 @@
+@node Maintenance, Platform, Installation, Top
+@c %MENU% How to enhance and port the GNU C Library
+@appendix Library Maintenance
+
+@menu
+* Source Layout::         How to add new functions or header files
+                             to the GNU C Library.
+* Porting::               How to port the GNU C Library to
+                             a new machine or operating system.
+@end menu
+
+@node Source Layout
+@appendixsec Adding New Functions
+
+The process of building the library is driven by the makefiles, which
+make heavy use of special features of GNU @code{make}.  The makefiles
+are very complex, and you probably don't want to try to understand them.
+But what they do is fairly straightforward, and only requires that you
+define a few variables in the right places.
+
+The library sources are divided into subdirectories, grouped by topic.
+
+The @file{string} subdirectory has all the string-manipulation
+functions, @file{math} has all the mathematical functions, etc.
+
+Each subdirectory contains a simple makefile, called @file{Makefile},
+which defines a few @code{make} variables and then includes the global
+makefile @file{Rules} with a line like:
+
+@smallexample
+include ../Rules
+@end smallexample
+
+@noindent
+The basic variables that a subdirectory makefile defines are:
+
+@table @code
+@item subdir
+The name of the subdirectory, for example @file{stdio}.
+This variable @strong{must} be defined.
+
+@item headers
+The names of the header files in this section of the library,
+such as @file{stdio.h}.
+
+@item routines
+@itemx aux
+The names of the modules (source files) in this section of the library.
+These should be simple names, such as @samp{strlen} (rather than
+complete file names, such as @file{strlen.c}).  Use @code{routines} for
+modules that define functions in the library, and @code{aux} for
+auxiliary modules containing things like data definitions.  But the
+values of @code{routines} and @code{aux} are just concatenated, so there
+really is no practical difference.@refill
+
+@item tests
+The names of test programs for this section of the library.  These
+should be simple names, such as @samp{tester} (rather than complete file
+names, such as @file{tester.c}).  @w{@samp{make tests}} will build and
+run all the test programs.  If a test program needs input, put the test
+data in a file called @file{@var{test-program}.input}; it will be given to
+the test program on its standard input.  If a test program wants to be
+run with arguments, put the arguments (all on a single line) in a file
+called @file{@var{test-program}.args}.  Test programs should exit with
+zero status when the test passes, and nonzero status when the test
+indicates a bug in the library or error in building.
+
+@item others
+The names of ``other'' programs associated with this section of the
+library.  These are programs which are not tests per se, but are other
+small programs included with the library.  They are built by
+@w{@samp{make others}}.@refill
+
+@item install-lib
+@itemx install-data
+@itemx install
+Files to be installed by @w{@samp{make install}}.  Files listed in
+@samp{install-lib} are installed in the directory specified by
+@samp{libdir} in @file{configparms} or @file{Makeconfig}
+(@pxref{Installation}).  Files listed in @code{install-data} are
+installed in the directory specified by @samp{datadir} in
+@file{configparms} or @file{Makeconfig}.  Files listed in @code{install}
+are installed in the directory specified by @samp{bindir} in
+@file{configparms} or @file{Makeconfig}.@refill
+
+@item distribute
+Other files from this subdirectory which should be put into a
+distribution tar file.  You need not list here the makefile itself or
+the source and header files listed in the other standard variables.
+Only define @code{distribute} if there are files used in an unusual way
+that should go into the distribution.
+
+@item generated
+Files which are generated by @file{Makefile} in this subdirectory.
+These files will be removed by @w{@samp{make clean}}, and they will
+never go into a distribution.
+
+@item extra-objs
+Extra object files which are built by @file{Makefile} in this
+subdirectory.  This should be a list of file names like @file{foo.o};
+the files will actually be found in whatever directory object files are
+being built in.  These files will be removed by @w{@samp{make clean}}.
+This variable is used for secondary object files needed to build
+@code{others} or @code{tests}.
+@end table
+
+@menu
+* Platform: Adding Platform-specific.             Adding platform-specific
+                                         features.
+@end menu
+
+@node Adding Platform-specific
+@appendixsubsec Platform-specific types, macros and functions
+
+It's sometimes necessary to provide nonstandard, platform-specific
+features to developers.  The C library is traditionally the
+lowest library layer, so it makes sense for it to provide these
+low-level features.  However, including these features in the C
+library may be a disadvantage if another package provides them
+as well as there will be two conflicting versions of them.  Also,
+the features won't be available to projects that do not use
+@theglibc{} but use other GNU tools, like GCC.
+
+The current guidelines are:
+@itemize @bullet
+@item
+If the header file provides features that only make sense on a particular
+machine architecture and have nothing to do with an operating system, then
+the features should ultimately be provided as GCC built-in functions.  Until
+then, @theglibc{} may provide them in the header file.  When the GCC built-in
+functions become available, those provided in the header file should be made
+conditionally available prior to the GCC version in which the built-in
+function was made available.
+
+@item
+If the header file provides features that are specific to an operating system,
+both GCC and @theglibc{} could provide it, but @theglibc{} is preferred
+as it already has a lot of information about the operating system.
+
+@item
+If the header file provides features that are specific to an operating system
+but used by @theglibc{}, then @theglibc{} should provide them.
+@end itemize
+
+The general solution for providing low-level features is to export them as
+follows:
+
+@itemize @bullet
+@item
+A nonstandard, low-level header file that defines macros and inline
+functions should be called @file{sys/platform/@var{name}.h}.
+
+@item
+Each header file's name should include the platform name, to avoid
+users thinking there is anything in common between the different
+header files for different platforms.  For example, a
+@file{sys/platform/@var{arch}.h} name such as
+@file{sys/platform/ppc.h} is better than @file{sys/platform.h}.
+
+@item
+A platform-specific header file provided by @theglibc{} should coordinate
+with GCC such that compiler built-in versions of the functions and macros are
+preferred if available.  This means that user programs will only ever need to
+include @file{sys/platform/@var{arch}.h}, keeping the same names of types,
+macros, and functions for convenience and portability.
+
+@item
+Each included symbol must have the prefix @code{__@var{arch}_}, such as
+@code{__ppc_get_timebase}.
+@end itemize
+
+
+The easiest way to provide a header file is to add it to the
+@code{sysdep_headers} variable.  For example, the combination of
+Linux-specific header files on PowerPC could be provided like this:
+
+@smallexample
+sysdep_headers += sys/platform/ppc.h
+@end smallexample
+
+Then ensure that you have added a @file{sys/platform/ppc.h}
+header file in the machine-specific directory, e.g.,
+@file{sysdeps/powerpc/sys/platform/ppc.h}.
+
+
+@node Porting
+@appendixsec Porting @theglibc{}
+
+@Theglibc{} is written to be easily portable to a variety of
+machines and operating systems.  Machine- and operating system-dependent
+functions are well separated to make it easy to add implementations for
+new machines or operating systems.  This section describes the layout of
+the library source tree and explains the mechanisms used to select
+machine-dependent code to use.
+
+All the machine-dependent and operating system-dependent files in the
+library are in the subdirectory @file{sysdeps} under the top-level
+library source directory.  This directory contains a hierarchy of
+subdirectories (@pxref{Hierarchy Conventions}).
+
+Each subdirectory of @file{sysdeps} contains source files for a
+particular machine or operating system, or for a class of machine or
+operating system (for example, systems by a particular vendor, or all
+machines that use IEEE 754 floating-point format).  A configuration
+specifies an ordered list of these subdirectories.  Each subdirectory
+implicitly appends its parent directory to the list.  For example,
+specifying the list @file{unix/bsd/vax} is equivalent to specifying the
+list @file{unix/bsd/vax unix/bsd unix}.  A subdirectory can also specify
+that it implies other subdirectories which are not directly above it in
+the directory hierarchy.  If the file @file{Implies} exists in a
+subdirectory, it lists other subdirectories of @file{sysdeps} which are
+appended to the list, appearing after the subdirectory containing the
+@file{Implies} file.  Lines in an @file{Implies} file that begin with a
+@samp{#} character are ignored as comments.  For example,
+@file{unix/bsd/Implies} contains:@refill
+@smallexample
+# BSD has Internet-related things.
+unix/inet
+@end smallexample
+@noindent
+and @file{unix/Implies} contains:
+@need 300
+@smallexample
+posix
+@end smallexample
+
+@noindent
+So the final list is @file{unix/bsd/vax unix/bsd unix/inet unix posix}.
+
+@file{sysdeps} has a ``special'' subdirectory called @file{generic}.  It
+is always implicitly appended to the list of subdirectories, so you
+needn't put it in an @file{Implies} file, and you should not create any
+subdirectories under it intended to be new specific categories.
+@file{generic} serves two purposes.  First, the makefiles do not bother
+to look for a system-dependent version of a file that's not in
+@file{generic}.  This means that any system-dependent source file must
+have an analogue in @file{generic}, even if the routines defined by that
+file are not implemented on other platforms.  Second, the @file{generic}
+version of a system-dependent file is used if the makefiles do not find
+a version specific to the system you're compiling for.
+
+If it is possible to implement the routines in a @file{generic} file in
+machine-independent C, using only other machine-independent functions in
+the C library, then you should do so.  Otherwise, make them stubs.  A
+@dfn{stub} function is a function which cannot be implemented on a
+particular machine or operating system.  Stub functions always return an
+error, and set @code{errno} to @code{ENOSYS} (Function not implemented).
+@xref{Error Reporting}.  If you define a stub function, you must place
+the statement @code{stub_warning(@var{function})}, where @var{function}
+is the name of your function, after its definition.  This causes the
+function to be listed in the installed @code{<gnu/stubs.h>}, and
+makes GNU ld warn when the function is used.
+
+Some rare functions are only useful on specific systems and aren't
+defined at all on others; these do not appear anywhere in the
+system-independent source code or makefiles (including the
+@file{generic} directory), only in the system-dependent @file{Makefile}
+in the specific system's subdirectory.
+
+If you come across a file that is in one of the main source directories
+(@file{string}, @file{stdio}, etc.), and you want to write a machine- or
+operating system-dependent version of it, move the file into
+@file{sysdeps/generic} and write your new implementation in the
+appropriate system-specific subdirectory.  Note that if a file is to be
+system-dependent, it @strong{must not} appear in one of the main source
+directories.@refill
+
+There are a few special files that may exist in each subdirectory of
+@file{sysdeps}:
+
+@comment Blank lines after items make the table look better.
+@table @file
+@item Makefile
+
+A makefile for this machine or operating system, or class of machine or
+operating system.  This file is included by the library makefile
+@file{Makerules}, which is used by the top-level makefile and the
+subdirectory makefiles.  It can change the variables set in the
+including makefile or add new rules.  It can use GNU @code{make}
+conditional directives based on the variable @samp{subdir} (see above) to
+select different sets of variables and rules for different sections of
+the library.  It can also set the @code{make} variable
+@samp{sysdep-routines}, to specify extra modules to be included in the
+library.  You should use @samp{sysdep-routines} rather than adding
+modules to @samp{routines} because the latter is used in determining
+what to distribute for each subdirectory of the main source tree.@refill
+
+Each makefile in a subdirectory in the ordered list of subdirectories to
+be searched is included in order.  Since several system-dependent
+makefiles may be included, each should append to @samp{sysdep-routines}
+rather than simply setting it:
+
+@smallexample
+sysdep-routines := $(sysdep-routines) foo bar
+@end smallexample
+
+@need 1000
+@item Subdirs
+
+This file contains the names of new whole subdirectories under the
+top-level library source tree that should be included for this system.
+These subdirectories are treated just like the system-independent
+subdirectories in the library source tree, such as @file{stdio} and
+@file{math}.
+
+Use this when there are completely new sets of functions and header
+files that should go into the library for the system this subdirectory
+of @file{sysdeps} implements.  For example,
+@file{sysdeps/unix/inet/Subdirs} contains @file{inet}; the @file{inet}
+directory contains various network-oriented operations which only make
+sense to put in the library on systems that support the Internet.@refill
+
+@item configure
+
+This file is a shell script fragment to be run at configuration time.
+The top-level @file{configure} script uses the shell @code{.} command to
+read the @file{configure} file in each system-dependent directory
+chosen, in order.  The @file{configure} files are often generated from
+@file{configure.ac} files using Autoconf.
+
+A system-dependent @file{configure} script will usually add things to
+the shell variables @samp{DEFS} and @samp{config_vars}; see the
+top-level @file{configure} script for details.  The script can check for
+@w{@samp{--with-@var{package}}} options that were passed to the
+top-level @file{configure}.  For an option
+@w{@samp{--with-@var{package}=@var{value}}} @file{configure} sets the
+shell variable @w{@samp{with_@var{package}}} (with any dashes in
+@var{package} converted to underscores) to @var{value}; if the option is
+just @w{@samp{--with-@var{package}}} (no argument), then it sets
+@w{@samp{with_@var{package}}} to @samp{yes}.
+
+@item configure.ac
+
+This file is an Autoconf input fragment to be processed into the file
+@file{configure} in this subdirectory.  @xref{Introduction,,,
+autoconf.info, Autoconf: Generating Automatic Configuration Scripts},
+for a description of Autoconf.  You should write either @file{configure}
+or @file{configure.ac}, but not both.  The first line of
+@file{configure.ac} should invoke the @code{m4} macro
+@samp{GLIBC_PROVIDES}.  This macro does several @code{AC_PROVIDE} calls
+for Autoconf macros which are used by the top-level @file{configure}
+script; without this, those macros might be invoked again unnecessarily
+by Autoconf.
+@end table
+
+That is the general system for how system-dependencies are isolated.
+@iftex
+The next section explains how to decide what directories in
+@file{sysdeps} to use.  @ref{Porting to Unix}, has some tips on porting
+the library to Unix variants.
+@end iftex
+
+@menu
+* Hierarchy Conventions::       The layout of the @file{sysdeps} hierarchy.
+* Porting to Unix::             Porting the library to an average
+                                   Unix-like system.
+@end menu
+
+@node Hierarchy Conventions
+@appendixsubsec Layout of the @file{sysdeps} Directory Hierarchy
+
+A GNU configuration name has three parts: the CPU type, the
+manufacturer's name, and the operating system.  @file{configure} uses
+these to pick the list of system-dependent directories to look for.  If
+the @samp{--nfp} option is @emph{not} passed to @file{configure}, the
+directory @file{@var{machine}/fpu} is also used.  The operating system
+often has a @dfn{base operating system}; for example, if the operating
+system is @samp{Linux}, the base operating system is @samp{unix/sysv}.
+The algorithm used to pick the list of directories is simple:
+@file{configure} makes a list of the base operating system,
+manufacturer, CPU type, and operating system, in that order.  It then
+concatenates all these together with slashes in between, to produce a
+directory name; for example, the configuration @w{@samp{i686-linux-gnu}}
+results in @file{unix/sysv/linux/i386/i686}.  @file{configure} then
+tries removing each element of the list in turn, so
+@file{unix/sysv/linux} and @file{unix/sysv} are also tried, among others.
+Since the precise version number of the operating system is often not
+important, and it would be very inconvenient, for example, to have
+identical @file{irix6.2} and @file{irix6.3} directories,
+@file{configure} tries successively less specific operating system names
+by removing trailing suffixes starting with a period.
+
+As an example, here is the complete list of directories that would be
+tried for the configuration @w{@samp{i686-linux-gnu}} (with the
+@file{crypt} and @file{linuxthreads} add-on):
+
+@smallexample
+sysdeps/i386/elf
+crypt/sysdeps/unix
+linuxthreads/sysdeps/unix/sysv/linux
+linuxthreads/sysdeps/pthread
+linuxthreads/sysdeps/unix/sysv
+linuxthreads/sysdeps/unix
+linuxthreads/sysdeps/i386/i686
+linuxthreads/sysdeps/i386
+linuxthreads/sysdeps/pthread/no-cmpxchg
+sysdeps/unix/sysv/linux/i386
+sysdeps/unix/sysv/linux
+sysdeps/gnu
+sysdeps/unix/common
+sysdeps/unix/mman
+sysdeps/unix/inet
+sysdeps/unix/sysv/i386/i686
+sysdeps/unix/sysv/i386
+sysdeps/unix/sysv
+sysdeps/unix/i386
+sysdeps/unix
+sysdeps/posix
+sysdeps/i386/i686
+sysdeps/i386/i486
+sysdeps/libm-i387/i686
+sysdeps/i386/fpu
+sysdeps/libm-i387
+sysdeps/i386
+sysdeps/wordsize-32
+sysdeps/ieee754
+sysdeps/libm-ieee754
+sysdeps/generic
+@end smallexample
+
+Different machine architectures are conventionally subdirectories at the
+top level of the @file{sysdeps} directory tree.  For example,
+@w{@file{sysdeps/sparc}} and @w{@file{sysdeps/m68k}}.  These contain
+files specific to those machine architectures, but not specific to any
+particular operating system.  There might be subdirectories for
+specializations of those architectures, such as
+@w{@file{sysdeps/m68k/68020}}.  Code which is specific to the
+floating-point coprocessor used with a particular machine should go in
+@w{@file{sysdeps/@var{machine}/fpu}}.
+
+There are a few directories at the top level of the @file{sysdeps}
+hierarchy that are not for particular machine architectures.
+
+@table @file
+@item generic
+As described above (@pxref{Porting}), this is the subdirectory
+that every configuration implicitly uses after all others.
+
+@item ieee754
+This directory is for code using the IEEE 754 floating-point format,
+where the C type @code{float} is IEEE 754 single-precision format, and
+@code{double} is IEEE 754 double-precision format.  Usually this
+directory is referred to in the @file{Implies} file in a machine
+architecture-specific directory, such as @file{m68k/Implies}.
+
+@item libm-ieee754
+This directory contains an implementation of a mathematical library
+usable on platforms which use @w{IEEE 754} conformant floating-point
+arithmetic.
+
+@item libm-i387
+This is a special case.  Ideally the code should be in
+@file{sysdeps/i386/fpu} but for various reasons it is kept aside.
+
+@item posix
+This directory contains implementations of things in the library in
+terms of @sc{POSIX.1} functions.  This includes some of the @sc{POSIX.1}
+functions themselves.  Of course, @sc{POSIX.1} cannot be completely
+implemented in terms of itself, so a configuration using just
+@file{posix} cannot be complete.
+
+@item unix
+This is the directory for Unix-like things.  @xref{Porting to Unix}.
+@file{unix} implies @file{posix}.  There are some special-purpose
+subdirectories of @file{unix}:
+
+@table @file
+@item unix/common
+This directory is for things common to both BSD and System V release 4.
+Both @file{unix/bsd} and @file{unix/sysv/sysv4} imply @file{unix/common}.
+
+@item unix/inet
+This directory is for @code{socket} and related functions on Unix systems.
+@file{unix/inet/Subdirs} enables the @file{inet} top-level subdirectory.
+@file{unix/common} implies @file{unix/inet}.
+@end table
+
+@item mach
+This is the directory for things based on the Mach microkernel from CMU
+(including @gnuhurdsystems{}).  Other basic operating systems
+(VMS, for example) would have their own directories at the top level of
+the @file{sysdeps} hierarchy, parallel to @file{unix} and @file{mach}.
+@end table
+
+@node Porting to Unix
+@appendixsubsec Porting @theglibc{} to Unix Systems
+
+Most Unix systems are fundamentally very similar.  There are variations
+between different machines, and variations in what facilities are
+provided by the kernel.  But the interface to the operating system
+facilities is, for the most part, pretty uniform and simple.
+
+The code for Unix systems is in the directory @file{unix}, at the top
+level of the @file{sysdeps} hierarchy.  This directory contains
+subdirectories (and subdirectory trees) for various Unix variants.
+
+The functions which are system calls in most Unix systems are
+implemented in assembly code, which is generated automatically from
+specifications in files named @file{syscalls.list}.  There are several
+such files, one in @file{sysdeps/unix} and others in its subdirectories.
+Some special system calls are implemented in files that are named with a
+suffix of @samp{.S}; for example, @file{_exit.S}.  Files ending in
+@samp{.S} are run through the C preprocessor before being fed to the
+assembler.
+
+These files all use a set of macros that should be defined in
+@file{sysdep.h}.  The @file{sysdep.h} file in @file{sysdeps/unix}
+partially defines them; a @file{sysdep.h} file in another directory must
+finish defining them for the particular machine and operating system
+variant.  See @file{sysdeps/unix/sysdep.h} and the machine-specific
+@file{sysdep.h} implementations to see what these macros are and what
+they should do.@refill
+
+The system-specific makefile for the @file{unix} directory
+(@file{sysdeps/unix/Makefile}) gives rules to generate several files
+from the Unix system you are building the library on (which is assumed
+to be the target system you are building the library @emph{for}).  All
+the generated files are put in the directory where the object files are
+kept; they should not affect the source tree itself.  The files
+generated are @file{ioctls.h}, @file{errnos.h}, @file{sys/param.h}, and
+@file{errlist.c} (for the @file{stdio} section of the library).
+
+@ignore
+@c This section might be a good idea if it is finished,
+@c but there's no point including it as it stands. --rms
+@c @appendixsec Compatibility with Traditional C
+
+@c ??? This section is really short now.  Want to keep it? --roland
+
+@c It's not anymore true.  glibc 2.1 cannot be used with K&R compilers.
+@c --drepper
+
+Although @theglibc{} implements the @w{ISO C} library facilities, you
+@emph{can} use @theglibc{} with traditional, ``pre-ISO'' C
+compilers.  However, you need to be careful because the content and
+organization of the @glibcadj{} header files differs from that of
+traditional C implementations.  This means you may need to make changes
+to your program in order to get it to compile.
+@end ignore