This is Info file INSTALL, produced by Makeinfo-1.44 from the input
file manual/maint.texinfo.


Library Maintenance
********************



How to Install the GNU C Library
=================================

   Installation of the GNU C library is relatively simple.

   You need the latest version of GNU `make'.  If you do not have GNU
`make', life is more difficult.  We recommend porting GNU `make' to
your system rather than trying to install the GNU C library without
it.  *Really.*

   To configure the GNU C library for your system, run the script
`configure' with `sh'.  You must give as an argument to the script a
word describing your system, such as `sun4' or `hp300'.

   By default, the `configure' script will set things up to build
things into a subdirectory of the library source directory whose name
is the name of the system you configure for.  For example,
`configure sun4' creates and uses a directory called `sun4'.  If you
give a second argument to `configure', that is used as the directory
name instead.

   You can build for several machines from the same source directory,
by specifying the subdirectory that `configure' created when you
configured for that machine in the `make' variable `ARCH'.  For
example, use `make ARCH=sun4', or put `ARCH=sun4' in your environment.
 If you don't specify a value for `ARCH', the variable `machine' is
used if defined; otherwise `make' will build for the configuration
most recently configured for.

   Now edit the file `Makeconfig' to set the compilation parameters,
and what directories to install the library and header files in.  See
the comments in `Makeconfig' for the details.  If you are building for
several machines, you can put just the values specific to a particular
machine in a file called `Makeconfig' in the object directory for that
machine (for example, `sun4/Makeconfig').  This should *not* be an
edited copy of `Makeconfig'.  Make a new file containing just the
variables in `Makeconfig' that you want to set specially for the
particular machine.  These values will override the values defined in
`Makeconfig'.

   Some of the machine-dependent code for some machines uses
extensions in the GNU C compiler, so you may need to compile the
library with GCC.  (In fact, all of the existing complete ports
require GCC.)  If possible, you should use the GNU linker, GNU `ld',
when linking programs with the GNU C library.  If you are going to use
GNU `ld', be sure to specify `-DHAVE_GNU_LD' in `Makeconfig'.

   To build the library and header files, type `make'.  This will
produce a lot of output, some of which looks like errors from `make'
(but isn't).  Look for error messages from `make' containing `***'. 
Those indicate that something is really wrong.  Using the `-w' option
to `make' may make the output easier to understand (this option tells
`make' to print messages telling you what subdirectories it is working
on).

   To install the library and header files, type `make install', after
setting the installation directories in `Makeconfig' (or
`MACHINE/Makeconfig').  This will build things if necessary, before
installing them.


Reporting Bugs
===============

   There are probably bugs in the GNU C library.  If you report them,
they will get fixed.  If you don't, no one will ever know about them
and they will remain unfixed for all eternity, if not longer.

   To report a bug, first you must find it.  Hopefully, this will be
the hard part.  Once you've found a bug, make sure it's really a bug. 
A good way to do this is to see if the GNU C library behaves the same
way some other C library does.  If so, probably you are wrong and the
libraries are right.  If not, one of the libraries is probably wrong.

   Once you're sure you've found a bug, try to narrow it down to the
smallest test case that reproduces the problem.  In the case of a C
library, you really only need to narrow it down to one library
function call, if possible.  This should not be too difficult.

   The final step when you have a simple test case is to report the
bug.  When reporting a bug, send your test case, the results you got,
the results you expected, what you think the problem might be (if
you've thought of anything), your system type, and the version of the
GNU C library which you are using.

   If you think you have found some way in which the GNU C library
does not conform to the ANSI and POSIX standards (*note Standards and
Portability::.), that is definitely a bug.  Report it!

   Send bug reports to Internet address `bug-gnu-libc@prep.ai.mit.edu'
or UUCP path `mit-eddie!prep.ai.mit.edu!bug-gnu-libc'.  If you have
other problems with installation, use, or the documentation, please
report those as well.


Porting the GNU C Library
==========================

   The GNU C library 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.

   The process of building the library is driven by the makefiles,
which make heavy use of GNU `make' features.  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 `string' subdirectory has all the string-manipulation
functions, `stdio' has all the standard I/O functions, etc.

   Each subdirectory contains a simple makefile, called `Makefile',
which defines a few `make' variables and then includes the global
makefile `Rules' with a line like:

     include ../Rules

The basic variables that a subdirectory makefile defines are:

`subdir'
     The name of the subdirectory, for example `stdio'.  This variable
     *must* be defined.

`headers'
     The names of the header files in this section of the library,
     such as `stdio.h'.

`routines'
`aux'
     The names of the modules (source files) in this section of the
     library.  These should be simple names, such as `strlen' (rather
     than complete file names, such as `strlen.c').  The idea is that
     `routines' is for modules that define functions in the library,
     and `aux' is for auxiliary modules containing things like data
     definitions.  But the values of `routines' and `aux' are
     concatenated, so there really is no practical difference.

`tests'
     The names of test programs for this section of the library.  These
     should be simple names, such as `tester' (rather than complete
     file names, such as `tester.c').  `make tests' will build and run
     all the test programs.  If a test program needs input, put the
     test data in a file called `TEST-PROGRAM.input'; it will 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 `TEST-PROGRAM.args'.

`others'
     The names of "other" in 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.  These are
     built by `make others'.

`install-lib'
`install-data'
`install'
     Files to be installed by `make install'.  Things listed in
     `install-lib' are installed in the directory specified by
     `libdir' in `Makeconfig' (*note Installation::.).  Things listed
     in `install-data' are installed in the directory specified by
     `datadir' in `Makeconfig'.  Things listed in `install' are
     installed in the directory specified by `bindir' in `Makeconfig'.

`distribute'
     Other files from this subdirectory which should be put into a
     distribution tar file.  The source and header files listed in the
     other standard variables, and the makefile itself, need not be
     listed here.  Only define `distribute' if there are files used in
     an unusual way that should go into the distribution.

   All the machine-dependent and operating system-dependent files in
the library are in the subdirectory `sysdeps' under the top-level
library source directory.  This directory contains a hierarchy of
directories.  Each subdirectory of `sysdeps' contains source files for
a particular machine or operating system, or for a class of machine or
operating system.  A configuration is specified by an ordered list of
these subdirectories.  Each subdirectory implicitly appends its parent
directory to the list.  For example, specifying the list
`unix/bsd/hp9k3bsd' is equivalent to specifying the list
`unix/bsd/hp9k3bsd 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 `Implies' exists in a
subdirectory, it lists other subdirectories of `sysdeps' which are
appended to the list, appearing after the subdirectory containing the
`Implies' file.  Lines in an `Implies' file that begin with a `#'
character are ignored as comments.  For example,
`unix/bsd/hp9k3bsd/Implies' contains:

     # HP 9000 series 300 is 68k.
     m68k

Since `m68k/Implies' contains:

     # 68k uses IEEE 754 floating point.
     ieee754

and `unix/bsd/Implies' contains:

     # BSD has Internet-related things.
     unix/inet

   and `unix/Implies' contains:

     posix

the final list is ` unix/bsd/hp9k3bsd unix/bsd m68k unix/inet unix
ieee754 posix '.

   There are two "special" subdirectories of `sysdeps', `generic' and
`stub'.  These two are always implicitly appended to the list of
subdirectories (in that order), so you needn't put them in an
`Implies' file, and you should not create any subdirectories under
them.  `generic' is for things that can be implemented in
machine-independent C, using only other machine-independent functions
in the C library.  `stub' is for "stub" versions of functions which
cannot be implemented on a particular machine or operating system. 
These functions always return an error, and set `errno' to `ENOSYS'
(Function not implemented).  A source file is known to be
system-dependent by its having a version in `generic' or `stub', so
every system-dependent function should have a generic or stub
implementation (there is no point in having both).  If you come across
a file that is in one of the main source directories (`string',
`stdio', etc.), and you want to write a machine- or operating
system-dependent version of it, move the file into `sysdeps/generic'
and write your new implementation in the appropriate system-specific
subdirectory.  Note that if a file is to be system-dependent, it *must
not* appear in one of the main source directories.

   There are a few special files that may exist in each subdirectory of
`sysdeps':

`Makefile'
     A makefile for this machine or operating system, or class of
     machine or operating system.  This file is included by the
     library makefile `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 `make' conditional commands based on the variable
     `subdir' (see above) to select different sets of variables and
     rules for different sections of the library.  It can also set the
     `make' variable `sysdep-routines', to specify extra modules to be
     included in the library.  You should use `sysdep-routines' rather
     than adding modules to `routines' because the latter is used in
     determining what to distribute for each subdirectory of the main
     source tree.

     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 `sysdep-routines' rather than simply setting it:

          sysdep-routines := $(sysdep-routines) foo bar

`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 `stdio' and `math'.  Use this when there are whole new
     sets of routines and header files that should go into the library
     for the system this subdirectory of `sysdeps' implements.  For
     example, `sysdeps/unix/inet/Subdirs' contains `inet'; the `inet'
     directory contains various network-oriented operations which only
     make sense to put in the library on systems that support the
     Internet.

`Dist'
     This file contains the names of files (relative the the
     subdirectory of `sysdeps' in which it appears) which should be
     included in the distribution.  List any new files used by rules
     in the `Makefile' in the same directory, or header files used by
     the source files in that directory.  You don't need to list files
     that are implementations (either C or assembly source) of
     routines whose names are given in the machine-independent
     makefiles in the main source tree.

   That is the general system for how system-dependencies are isolated. 
The rest of this section describes details of particular
implementations for classes of systems, and how existing classes and
systems are organized.



The Layout of the `sysdeps' Directory Hierarchy
------------------------------------------------

   Different machine architectures are generally at the top level of
the `sysdeps' hierarchy.  For example, `sysdeps/sparc' and
`sysdeps/m68k'.  These contain things specific to those machine
architectures (perhaps with subdirectories for specialization of those
architectures, such as `sysdeps/m68k/68881'), but not specific to any
particular operating system.

   Things specific to a particular operating system on a particular
machine are canonically put in a subdirectory in the section of the
hierarchy for the operating system, usually with an `Implies' file
referring to the top-level subdirectory under `sysdeps' for the
particular machine.  For example, `unix/bsd/hp9k3bsd' implies `m68k'.

   There are a few directories at the top level of the `sysdeps'
hierarchy that are not for particular machine architectures.

`generic'
`stub'
     As described above (*note Porting::.), these are the two
     subdirectories that every configuration uses, usually last.

`ieee754'
     This directory is for code using the IEEE 754 floating-point
     format, where the C type `float' is IEEE 754 single-precision
     format, and `double' is IEEE 754 double-precision format. 
     Usually this is directory is referred to in the `Implies' file in
     a machine architecture-specific directory, such as `m68k/Implies'.

`posix'
     This directory contains implementations of things in the library
     in terms of POSIX.1 functions.  This includes some of the POSIX.1
     functions themselves.  Of course, POSIX.1 cannot be completely
     implemented in terms of itself, so a configuration using just
     `posix' cannot be complete.

`unix'
     This is the directory for Unix-like things.  See *Note Porting to
     Unix::.  `unix' implies `posix'.

`mach'
     This is the directory for things based on the Mach microkernel
     from CMU (including the GNU operating system).  Other basic
     operating systems (VMS, for example) would have their own
     directories at the top level of the `sysdeps' hierarchy, parallel
     to `unix' and `mach'.


Porting the GNU C Library 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 `unix', at the top
level of the `sysdeps' hierarchy.  This directory contains
subdirectories (and subdirectory trees) for various Unix variants.

   The routines which are system calls in most Unix systems are
implemented in assembly code in files in `sysdeps/unix'.  These files
are named with a suffix of `.S'; for example, `__open.S'.  Files ending
in `.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 `sysdep.h'.  The `sysdep.h' in `sysdeps/unix' does not adequately
define them.  They must be defined for the particular machine and
operating system variant.  See `sysdeps/unix/sysdep.h' and the
machine-specific `sysdep.h' implementations to see what these macros
are and what they should do.

   The system-specific makefile for the `unix' directory,
`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 *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: `ioctls.h', `errnos.h', `sys/param.h', and `errlist.c'
(for the `stdio' section of the library).


Compatibility with Traditional C
=================================

   Although the GNU C library implements the ANSI C library facilities,
you *can* use the GNU C library with traditional, "pre-ANSI" C
compilers.  However, there are a couple things you need to watch out
for.

   You must include a different set of header files when compiling your
program using a traditional C compiler than when compiling with an ANSI
C compiler.  (This is because traditional C compilers do not understand
the function prototypes used in the ANSI C header files.  On the other
hand, if you are using an ANSI C compiler like GCC, you should use the
ANSI C header files because the prototypes permit the compiler to do a
better job of detecting errors in calls to library functions.)  You can
tell the C compiler what directories to search for header files by
using the `-I' option.  Set the `trad-incldir' variable in
`Makeconfig' to choose where to install this set of header files.

   You also need to be careful because the content and organization of
the GNU C library 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.


Contributors to the GNU C Library
==================================

   The GNU C library was written almost entirely by Roland McGrath. 
Some parts of the library were contributed by other people.

   * The `getopt' and related functions were written by Richard
     Stallman, David J. MacKenzie, and Roland McGrath.

   * The random number generation functions `random', `srandom',
     `setstate' and `initstate', which are also the basis for the
     `rand' and `srand' functions, were written by Earl T. Cohen for
     the University of California at Berkeley and are copyrighted by
     the Regents of the University of California.  They have undergone
     minor changes to fit into the GNU C library and to fit the ANSI C
     standard, but the functional code is Berkeley's.

   * Most of the math functions are taken from 4.4 BSD, and are
     copyrighted by the Regents of the University of California.  They
     have been modified only slightly to work with the GNU C library.

   * The `qsort' function was written by Douglas C. Schmidt.

   * The memory allocation functions `malloc', `realloc' and `free'
     and related code were written by Michael J. Haertel.

   * Fast implementations of many of the string functions (`memcpy',
     `strlen', etc.) were written by Torbjorn Granlund.

   * Some of the support code for Mach is taken from Mach 3.0, from
     CMU, and is under the following copyright terms:

          Mach Operating System
          Copyright (c) 1991,1990,1989 Carnegie Mellon University
          All Rights Reserved.
          
          Permission to use, copy, modify and distribute this software and its
          documentation is hereby granted, provided that both the copyright
          notice and this permission notice appear in all copies of the
          software, derivative works or modified versions, and any portions
          thereof, and that both notices appear in supporting documentation.
          
          CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
          CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
          ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
          
          Carnegie Mellon requests users of this software to return to
          
           Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
           School of Computer Science
           Carnegie Mellon University
           Pittsburgh PA 15213-3890
          
          any improvements or extensions that they make and grant Carnegie Mellon
          the rights to redistribute these changes.

   * The `tar.h' header file was written by David J. MacKenzie.



Tag Table:
Node: Maintenance97
Node: Installation141
Node: Reporting Bugs3131
Node: Porting4714
Node: Hierarchy Conventions13569
Node: Porting to Unix15729
Node: Compatibility with Traditional C17429
Node: Contributors to the GNU C Library18645

End Tag Table
