doc/make-stds.texi

@comment This file is included by both standards.texi and make.texinfo.
@comment It was broken out of standards.texi on 1/6/93 by roland.

@node Makefile Conventions
@chapter Makefile Conventions
@cindex makefile, conventions for
@cindex conventions for makefiles
@cindex standards for makefiles

@c Copyright 1992, 1993, 1994, 1995, 1996, 1997, 1998, 2000, 2001,
@c 2004, 2005, 2006, 2007, 2008, 2010, 2013, 2014, 2015
@c Free Software Foundation, Inc.
@c
@c Permission is granted to copy, distribute and/or modify this document
@c under the terms of the GNU Free Documentation License, Version 1.3
@c or any later version published by the Free Software Foundation;
@c with no Invariant Sections, with no
@c Front-Cover Texts, and with no Back-Cover Texts.
@c A copy of the license is included in the section entitled ``GNU
@c Free Documentation License''.

This
@ifinfo
node
@end ifinfo
@iftex
@ifset CODESTD
section
@end ifset
@ifclear CODESTD
chapter
@end ifclear
@end iftex
describes conventions for writing the Makefiles for GNU programs.
Using Automake will help you write a Makefile that follows these
conventions.  For more information on portable Makefiles, see
@sc{posix} and @ref{Portable Make, Portable Make Programming,, autoconf,
Autoconf}.


@menu
* Makefile Basics::             General conventions for Makefiles.
* Utilities in Makefiles::      Utilities to be used in Makefiles.
* Command Variables::           Variables for specifying commands.
* DESTDIR::                     Supporting staged installs.
* Directory Variables::         Variables for installation directories.
* Standard Targets::            Standard targets for users.
* Install Command Categories::  Three categories of commands in the @samp{install}
                                  rule: normal, pre-install and post-install.
@end menu

@node Makefile Basics
@section General Conventions for Makefiles

Every Makefile should contain this line:

@example
SHELL = /bin/sh
@end example

@noindent
to avoid trouble on systems where the @code{SHELL} variable might be
inherited from the environment.  (This is never a problem with GNU
@code{make}.)

Different @code{make} programs have incompatible suffix lists and
implicit rules, and this sometimes creates confusion or misbehavior.  So
it is a good idea to set the suffix list explicitly using only the
suffixes you need in the particular Makefile, like this:

@example
.SUFFIXES:
.SUFFIXES: .c .o
@end example

@noindent
The first line clears out the suffix list, the second introduces all
suffixes which may be subject to implicit rules in this Makefile.

Don't assume that @file{.} is in the path for command execution.  When
you need to run programs that are a part of your package during the
make, please make sure that it uses @file{./} if the program is built as
part of the make or @file{$(srcdir)/} if the file is an unchanging part
of the source code.  Without one of these prefixes, the current search
path is used.

The distinction between @file{./} (the @dfn{build directory}) and
@file{$(srcdir)/} (the @dfn{source directory}) is important because
users can build in a separate directory using the @samp{--srcdir} option
to @file{configure}.  A rule of the form:

@smallexample
foo.1 : foo.man sedscript
        sed -f sedscript foo.man > foo.1
@end smallexample

@noindent
will fail when the build directory is not the source directory, because
@file{foo.man} and @file{sedscript} are in the source directory.

When using GNU @code{make}, relying on @samp{VPATH} to find the source
file will work in the case where there is a single dependency file,
since the @code{make} automatic variable @samp{$<} will represent the
source file wherever it is.  (Many versions of @code{make} set @samp{$<}
only in implicit rules.)  A Makefile target like

@smallexample
foo.o : bar.c
        $(CC) -I. -I$(srcdir) $(CFLAGS) -c bar.c -o foo.o
@end smallexample

@noindent
should instead be written as

@smallexample
foo.o : bar.c
        $(CC) -I. -I$(srcdir) $(CFLAGS) -c $< -o $@@
@end smallexample

@noindent
in order to allow @samp{VPATH} to work correctly.  When the target has
multiple dependencies, using an explicit @samp{$(srcdir)} is the easiest
way to make the rule work well.  For example, the target above for
@file{foo.1} is best written as:

@smallexample
foo.1 : foo.man sedscript
        sed -f $(srcdir)/sedscript $(srcdir)/foo.man > $@@
@end smallexample

GNU distributions usually contain some files which are not source
files---for example, Info files, and the output from Autoconf, Automake,
Bison or Flex.  Since these files normally appear in the source
directory, they should always appear in the source directory, not in the
build directory.  So Makefile rules to update them should put the
updated files in the source directory.

However, if a file does not appear in the distribution, then the
Makefile should not put it in the source directory, because building a
program in ordinary circumstances should not modify the source directory
in any way.

Try to make the build and installation targets, at least (and all their
subtargets) work correctly with a parallel @code{make}.

@node Utilities in Makefiles
@section Utilities in Makefiles

Write the Makefile commands (and any shell scripts, such as
@code{configure}) to run under @code{sh} (both the traditional Bourne
shell and the @sc{posix} shell), not @code{csh}.  Don't use any
special features of @code{ksh} or @code{bash}, or @sc{posix} features
not widely supported in traditional Bourne @code{sh}.

The @code{configure} script and the Makefile rules for building and
installation should not use any utilities directly except these:

@c dd find
@c gunzip gzip md5sum
@c mkfifo mknod tee uname

@example
awk cat cmp cp diff echo expr false grep install-info ln ls
mkdir mv printf pwd rm rmdir sed sleep sort tar test touch tr true
@end example

Compression programs such as @code{gzip} can be used in the
@code{dist} rule.

Generally, stick to the widely-supported (usually
@sc{posix}-specified) options and features of these programs.  For
example, don't use @samp{mkdir -p}, convenient as it may be, because a
few systems don't support it at all and with others, it is not safe
for parallel execution.  For a list of known incompatibilities, see
@ref{Portable Shell, Portable Shell Programming,, autoconf, Autoconf}.


It is a good idea to avoid creating symbolic links in makefiles, since a
few file systems don't support them.

The Makefile rules for building and installation can also use compilers
and related programs, but should do so via @code{make} variables so that the
user can substitute alternatives.  Here are some of the programs we
mean:

@example
ar bison cc flex install ld ldconfig lex
make makeinfo ranlib texi2pdf yacc
@end example

Use the following @code{make} variables to run those programs:

@example
$(AR) $(BISON) $(CC) $(FLEX) $(INSTALL) $(LD) $(LDCONFIG) $(LEX)
$(MAKE) $(MAKEINFO) $(RANLIB) $(TEXI2PDF) $(YACC)
@end example

When you use @code{ranlib} or @code{ldconfig}, you should make sure
nothing bad happens if the system does not have the program in question.
Arrange to ignore an error from that command, and print a message before
the command to tell the user that failure of this command does not mean
a problem.  (The Autoconf @samp{AC_PROG_RANLIB} macro can help with
this.)

If you use symbolic links, you should implement a fallback for systems
that don't have symbolic links.

Additional utilities that can be used via Make variables are:

@example
chgrp chmod chown mknod
@end example

It is ok to use other utilities in Makefile portions (or scripts)
intended only for particular systems where you know those utilities
exist.

@node Command Variables
@section Variables for Specifying Commands

Makefiles should provide variables for overriding certain commands, options,
and so on.

In particular, you should run most utility programs via variables.
Thus, if you use Bison, have a variable named @code{BISON} whose default
value is set with @samp{BISON = bison}, and refer to it with
@code{$(BISON)} whenever you need to use Bison.

File management utilities such as @code{ln}, @code{rm}, @code{mv}, and
so on, need not be referred to through variables in this way, since users
don't need to replace them with other programs.

Each program-name variable should come with an options variable that is
used to supply options to the program.  Append @samp{FLAGS} to the
program-name variable name to get the options variable name---for
example, @code{BISONFLAGS}.  (The names @code{CFLAGS} for the C
compiler, @code{YFLAGS} for yacc, and @code{LFLAGS} for lex, are
exceptions to this rule, but we keep them because they are standard.)
Use @code{CPPFLAGS} in any compilation command that runs the
preprocessor, and use @code{LDFLAGS} in any compilation command that
does linking as well as in any direct use of @code{ld}.

If there are C compiler options that @emph{must} be used for proper
compilation of certain files, do not include them in @code{CFLAGS}.
Users expect to be able to specify @code{CFLAGS} freely themselves.
Instead, arrange to pass the necessary options to the C compiler
independently of @code{CFLAGS}, by writing them explicitly in the
compilation commands or by defining an implicit rule, like this:

@smallexample
CFLAGS = -g
ALL_CFLAGS = -I. $(CFLAGS)
.c.o:
        $(CC) -c $(CPPFLAGS) $(ALL_CFLAGS) $<
@end smallexample

Do include the @samp{-g} option in @code{CFLAGS}, because that is not
@emph{required} for proper compilation.  You can consider it a default
that is only recommended.  If the package is set up so that it is
compiled with GCC by default, then you might as well include @samp{-O}
in the default value of @code{CFLAGS} as well.

Put @code{CFLAGS} last in the compilation command, after other variables
containing compiler options, so the user can use @code{CFLAGS} to
override the others.

@code{CFLAGS} should be used in every invocation of the C compiler,
both those which do compilation and those which do linking.

Every Makefile should define the variable @code{INSTALL}, which is the
basic command for installing a file into the system.

Every Makefile should also define the variables @code{INSTALL_PROGRAM}
and @code{INSTALL_DATA}.  (The default for @code{INSTALL_PROGRAM} should
be @code{$(INSTALL)}; the default for @code{INSTALL_DATA} should be
@code{$@{INSTALL@} -m 644}.)  Then it should use those variables as the
commands for actual installation, for executables and non-executables
respectively.  Minimal use of these variables is as follows:

@example
$(INSTALL_PROGRAM) foo $(bindir)/foo
$(INSTALL_DATA) libfoo.a $(libdir)/libfoo.a
@end example

However, it is preferable to support a @code{DESTDIR} prefix on the
target files, as explained in the next section.

It is acceptable, but not required, to install multiple files in one
command, with the final argument being a directory, as in:

@example
$(INSTALL_PROGRAM) foo bar baz $(bindir)
@end example


@node DESTDIR
@section @code{DESTDIR}: Support for Staged Installs

@vindex DESTDIR
@cindex staged installs
@cindex installations, staged

@code{DESTDIR} is a variable prepended to each installed target file,
like this:

@example
$(INSTALL_PROGRAM) foo $(DESTDIR)$(bindir)/foo
$(INSTALL_DATA) libfoo.a $(DESTDIR)$(libdir)/libfoo.a
@end example

The @code{DESTDIR} variable is specified by the user on the @code{make}
command line as an absolute file name.  For example:

@example
make DESTDIR=/tmp/stage install
@end example

@noindent
@code{DESTDIR} should be supported only in the @code{install*} and
@code{uninstall*} targets, as those are the only targets where it is
useful.

If your installation step would normally install
@file{/usr/local/bin/foo} and @file{/usr/@/local/@/lib/@/libfoo.a}, then an
installation invoked as in the example above would install
@file{/tmp/stage/usr/local/bin/foo} and
@file{/tmp/stage/usr/local/lib/libfoo.a} instead.

Prepending the variable @code{DESTDIR} to each target in this way
provides for @dfn{staged installs}, where the installed files are not
placed directly into their expected location but are instead copied
into a temporary location (@code{DESTDIR}).  However, installed files
maintain their relative directory structure and any embedded file names
will not be modified.

You should not set the value of @code{DESTDIR} in your @file{Makefile}
at all; then the files are installed into their expected locations by
default.  Also, specifying @code{DESTDIR} should not change the
operation of the software in any way, so its value should not be
included in any file contents.

@code{DESTDIR} support is commonly used in package creation.  It is
also helpful to users who want to understand what a given package will
install where, and to allow users who don't normally have permissions
to install into protected areas to build and install before gaining
those permissions.  Finally, it can be useful with tools such as
@code{stow}, where code is installed in one place but made to appear
to be installed somewhere else using symbolic links or special mount
operations.  So, we strongly recommend GNU packages support
@code{DESTDIR}, though it is not an absolute requirement.


@node Directory Variables
@section Variables for Installation Directories

Installation directories should always be named by variables, so it is
easy to install in a nonstandard place.  The standard names for these
variables and the values they should have in GNU packages are
described below.  They are based on a standard file system layout;
variants of it are used in GNU/Linux and other modern operating
systems.

Installers are expected to override these values when calling
@command{make} (e.g., @kbd{make prefix=/usr install}) or
@command{configure} (e.g., @kbd{configure --prefix=/usr}).  GNU
packages should not try to guess which value should be appropriate for
these variables on the system they are being installed onto: use the
default settings specified here so that all GNU packages behave
identically, allowing the installer to achieve any desired layout.

@cindex directories, creating installation
@cindex installation directories, creating
All installation directories, and their parent directories, should be
created (if necessary) before they are installed into.

These first two variables set the root for the installation.  All the
other installation directories should be subdirectories of one of
these two, and nothing should be directly installed into these two
directories.

@table @code
@item prefix
@vindex prefix
A prefix used in constructing the default values of the variables listed
below.  The default value of @code{prefix} should be @file{/usr/local}.
When building the complete GNU system, the prefix will be empty and
@file{/usr} will be a symbolic link to @file{/}.
(If you are using Autoconf, write it as @samp{@@prefix@@}.)

Running @samp{make install} with a different value of @code{prefix} from
the one used to build the program should @emph{not} recompile the
program.

@item exec_prefix
@vindex exec_prefix
A prefix used in constructing the default values of some of the
variables listed below.  The default value of @code{exec_prefix} should
be @code{$(prefix)}.
(If you are using Autoconf, write it as @samp{@@exec_prefix@@}.)

Generally, @code{$(exec_prefix)} is used for directories that contain
machine-specific files (such as executables and subroutine libraries),
while @code{$(prefix)} is used directly for other directories.

Running @samp{make install} with a different value of @code{exec_prefix}
from the one used to build the program should @emph{not} recompile the
program.
@end table

Executable programs are installed in one of the following directories.

@table @code
@item bindir
@vindex bindir
The directory for installing executable programs that users can run.
This should normally be @file{/usr/local/bin}, but write it as
@file{$(exec_prefix)/bin}.
(If you are using Autoconf, write it as @samp{@@bindir@@}.)

@item sbindir
@vindex sbindir
The directory for installing executable programs that can be run from
the shell, but are only generally useful to system administrators.  This
should normally be @file{/usr/local/sbin}, but write it as
@file{$(exec_prefix)/sbin}.
(If you are using Autoconf, write it as @samp{@@sbindir@@}.)

@item libexecdir
@vindex libexecdir
@comment This paragraph adjusted to avoid overfull hbox --roland 5jul94
The directory for installing executable programs to be run by other
programs rather than by users.  This directory should normally be
@file{/usr/local/libexec}, but write it as @file{$(exec_prefix)/libexec}.
(If you are using Autoconf, write it as @samp{@@libexecdir@@}.)

The definition of @samp{libexecdir} is the same for all packages, so
you should install your data in a subdirectory thereof.  Most packages
install their data under @file{$(libexecdir)/@var{package-name}/},
possibly within additional subdirectories thereof, such as
@file{$(libexecdir)/@var{package-name}/@var{machine}/@var{version}}.
@end table

Data files used by the program during its execution are divided into
categories in two ways.

@itemize @bullet
@item
Some files are normally modified by programs; others are never normally
modified (though users may edit some of these).

@item
Some files are architecture-independent and can be shared by all
machines at a site; some are architecture-dependent and can be shared
only by machines of the same kind and operating system; others may never
be shared between two machines.
@end itemize

This makes for six different possibilities.  However, we want to
discourage the use of architecture-dependent files, aside from object
files and libraries.  It is much cleaner to make other data files
architecture-independent, and it is generally not hard.

Here are the variables Makefiles should use to specify directories
to put these various kinds of files in:

@table @samp
@item datarootdir
The root of the directory tree for read-only architecture-independent
data files.  This should normally be @file{/usr/local/share}, but
write it as @file{$(prefix)/share}.  (If you are using Autoconf, write
it as @samp{@@datarootdir@@}.)  @samp{datadir}'s default value is
based on this variable; so are @samp{infodir}, @samp{mandir}, and
others.

@item datadir
The directory for installing idiosyncratic read-only
architecture-independent data files for this program.  This is usually
the same place as @samp{datarootdir}, but we use the two separate
variables so that you can move these program-specific files without
altering the location for Info files, man pages, etc.

@c raggedright  (not until next Texinfo release)
This should normally be @file{/usr/local/share}, but write it as
@file{$(datarootdir)}.  (If you are using Autoconf, write it as
@samp{@@datadir@@}.)
@c end raggedright

The definition of @samp{datadir} is the same for all packages, so you
should install your data in a subdirectory thereof.  Most packages
install their data under @file{$(datadir)/@var{package-name}/}.

@item sysconfdir
The directory for installing read-only data files that pertain to a
single machine--that is to say, files for configuring a host.  Mailer
and network configuration files, @file{/etc/passwd}, and so forth belong
here.  All the files in this directory should be ordinary ASCII text
files.  This directory should normally be @file{/usr/local/etc}, but
write it as @file{$(prefix)/etc}.
(If you are using Autoconf, write it as @samp{@@sysconfdir@@}.)

This directory is not the right place to install executables built by
running @samp{make}---they probably belong in @file{$(libexecdir)} or
@file{$(sbindir)}.  Also do not install here files that will be
modified in the normal course of their use (programs whose purpose is
to change the configuration of the system excluded).  Those probably
belong in @file{$(localstatedir)}.

@item sharedstatedir
The directory for installing architecture-independent data files which
the programs modify while they run.  This should normally be
@file{/usr/local/com}, but write it as @file{$(prefix)/com}.
(If you are using Autoconf, write it as @samp{@@sharedstatedir@@}.)

@item localstatedir
The directory for installing data files which the programs modify while
they run, and that pertain to one specific machine.  Users should never
need to modify files in this directory to configure the package's
operation; put such configuration information in separate files that go
in @file{$(datadir)} or @file{$(sysconfdir)}.  @file{$(localstatedir)}
should normally be @file{/usr/local/var}, but write it as
@file{$(prefix)/var}.
(If you are using Autoconf, write it as @samp{@@localstatedir@@}.)

@item runstatedir
The directory for installing data files which the programs modify
while they run, that pertain to one specific machine, and which need
not persist longer than the execution of the program---which is
generally long-lived, for example, until the next reboot.  PID files
for system daemons are a typical use.  In addition, this directory
should not be cleaned except perhaps at reboot, while the general
@file{/tmp} (@code{TMPDIR}) may be cleaned arbitrarily.  This should
normally be @file{/var/run}, but write it as
@file{$(localstatedir)/run}.  Having it as a separate variable allows
the use of @file{/run} if desired, for example.  (If you are using
Autoconf 2.70 or later, write it as @samp{@@runstatedir@@}.)
@end table

These variables specify the directory for installing certain specific
types of files, if your program has them.  Every GNU package should
have Info files, so every program needs @samp{infodir}, but not all
need @samp{libdir} or @samp{lispdir}.

@table @samp
@item includedir
The directory for installing header files to be included by user
programs with the C @samp{#include} preprocessor directive.  This
should normally be @file{/usr/local/include}, but write it as
@file{$(prefix)/include}.
(If you are using Autoconf, write it as @samp{@@includedir@@}.)

Most compilers other than GCC do not look for header files in directory
@file{/usr/local/include}.  So installing the header files this way is
only useful with GCC@.  Sometimes this is not a problem because some
libraries are only really intended to work with GCC@.  But some libraries
are intended to work with other compilers.  They should install their
header files in two places, one specified by @code{includedir} and one
specified by @code{oldincludedir}.

@item oldincludedir
The directory for installing @samp{#include} header files for use with
compilers other than GCC@.  This should normally be @file{/usr/include}.
(If you are using Autoconf, you can write it as @samp{@@oldincludedir@@}.)

The Makefile commands should check whether the value of
@code{oldincludedir} is empty.  If it is, they should not try to use
it; they should cancel the second installation of the header files.

A package should not replace an existing header in this directory unless
the header came from the same package.  Thus, if your Foo package
provides a header file @file{foo.h}, then it should install the header
file in the @code{oldincludedir} directory if either (1) there is no
@file{foo.h} there or (2) the @file{foo.h} that exists came from the Foo
package.

To tell whether @file{foo.h} came from the Foo package, put a magic
string in the file---part of a comment---and @code{grep} for that string.

@item docdir
The directory for installing documentation files (other than Info) for
this package.  By default, it should be
@file{/usr/local/share/doc/@var{yourpkg}}, but it should be written as
@file{$(datarootdir)/doc/@var{yourpkg}}.  (If you are using Autoconf,
write it as @samp{@@docdir@@}.)  The @var{yourpkg} subdirectory, which
may include a version number, prevents collisions among files with
common names, such as @file{README}.

@item infodir
The directory for installing the Info files for this package.  By
default, it should be @file{/usr/local/share/info}, but it should be
written as @file{$(datarootdir)/info}.  (If you are using Autoconf,
write it as @samp{@@infodir@@}.)  @code{infodir} is separate from
@code{docdir} for compatibility with existing practice.

@item htmldir
@itemx pdfdir
@itemx psdir
Directories for installing documentation files in the particular
format.  They should all be set to @code{$(docdir)} by default.  (If
you are using Autoconf, write them as @samp{@@htmldir@@},
etc.)  Packages which supply several translations
of their documentation should install them in
@samp{$(htmldir)/}@var{ll}, @samp{$(pdfdir)/}@var{ll}, etc. where
@var{ll} is a locale abbreviation such as @samp{en} or @samp{pt_BR}.

@item libdir
The directory for object files and libraries of object code.  Do not
install executables here, they probably ought to go in @file{$(libexecdir)}
instead.  The value of @code{libdir} should normally be
@file{/usr/local/lib}, but write it as @file{$(exec_prefix)/lib}.
(If you are using Autoconf, write it as @samp{@@libdir@@}.)

@item lispdir
The directory for installing any Emacs Lisp files in this package.  By
default, it should be @file{/usr/local/share/emacs/site-lisp}, but it
should be written as @file{$(datarootdir)/emacs/site-lisp}.

If you are using Autoconf, write the default as @samp{@@lispdir@@}.
In order to make @samp{@@lispdir@@} work, you need the following lines
in your @file{configure.ac} file:

@example
lispdir='$@{datarootdir@}/emacs/site-lisp'
AC_SUBST(lispdir)
@end example

@item localedir
The directory for installing locale-specific message catalogs for this
package.  By default, it should be @file{/usr/local/share/locale}, but
it should be written as @file{$(datarootdir)/locale}.  (If you are
using Autoconf, write it as @samp{@@localedir@@}.)  This directory
usually has a subdirectory per locale.
@end table

Unix-style man pages are installed in one of the following:

@table @samp
@item mandir
The top-level directory for installing the man pages (if any) for this
package.  It will normally be @file{/usr/local/share/man}, but you
should write it as @file{$(datarootdir)/man}.  (If you are using
Autoconf, write it as @samp{@@mandir@@}.)

@item man1dir
The directory for installing section 1 man pages.  Write it as
@file{$(mandir)/man1}.
@item man2dir
The directory for installing section 2 man pages.  Write it as
@file{$(mandir)/man2}
@item @dots{}

@strong{Don't make the primary documentation for any GNU software be a
man page.  Write a manual in Texinfo instead.  Man pages are just for
the sake of people running GNU software on Unix, which is a secondary
application only.}

@item manext
The file name extension for the installed man page.  This should contain
a period followed by the appropriate digit; it should normally be @samp{.1}.

@item man1ext
The file name extension for installed section 1 man pages.
@item man2ext
The file name extension for installed section 2 man pages.
@item @dots{}
Use these names instead of @samp{manext} if the package needs to install man
pages in more than one section of the manual.
@end table

And finally, you should set the following variable:

@table @samp
@item srcdir
The directory for the sources being compiled.  The value of this
variable is normally inserted by the @code{configure} shell script.
(If you are using Autoconf, use @samp{srcdir = @@srcdir@@}.)
@end table

For example:

@smallexample
@c I have changed some of the comments here slightly to fix an overfull
@c hbox, so the make manual can format correctly. --roland
# Common prefix for installation directories.
# NOTE: This directory must exist when you start the install.
prefix = /usr/local
datarootdir = $(prefix)/share
datadir = $(datarootdir)
exec_prefix = $(prefix)
# Where to put the executable for the command 'gcc'.
bindir = $(exec_prefix)/bin
# Where to put the directories used by the compiler.
libexecdir = $(exec_prefix)/libexec
# Where to put the Info files.
infodir = $(datarootdir)/info
@end smallexample

If your program installs a large number of files into one of the
standard user-specified directories, it might be useful to group them
into a subdirectory particular to that program.  If you do this, you
should write the @code{install} rule to create these subdirectories.

Do not expect the user to include the subdirectory name in the value of
any of the variables listed above.  The idea of having a uniform set of
variable names for installation directories is to enable the user to
specify the exact same values for several different GNU packages.  In
order for this to be useful, all the packages must be designed so that
they will work sensibly when the user does so.

At times, not all of these variables may be implemented in the current
release of Autoconf and/or Automake; but as of Autoconf@tie{}2.60, we
believe all of them are.  When any are missing, the descriptions here
serve as specifications for what Autoconf will implement.  As a
programmer, you can either use a development version of Autoconf or
avoid using these variables until a stable release is made which
supports them.


@node Standard Targets
@section Standard Targets for Users

All GNU programs should have the following targets in their Makefiles:

@table @samp
@item all
Compile the entire program.  This should be the default target.  This
target need not rebuild any documentation files; Info files should
normally be included in the distribution, and PDF (and other
documentation format) files should be made only when explicitly asked
for.

By default, the Make rules should compile and link with @samp{-g}, so
that executable programs have debugging symbols.  Otherwise, you are
essentially helpless in the face of a crash, and it is often far from
easy to reproduce with a fresh build.

@item install
Compile the program and copy the executables, libraries, and so on to
the file names where they should reside for actual use.  If there is a
simple test to verify that a program is properly installed, this target
should run that test.

Do not strip executables when installing them.  This helps eventual
debugging that may be needed later, and nowadays disk space is cheap
and dynamic loaders typically ensure debug sections are not loaded during
normal execution.  Users that need stripped binaries may invoke the
@code{install-strip} target to do that.

If possible, write the @code{install} target rule so that it does not
modify anything in the directory where the program was built, provided
@samp{make all} has just been done.  This is convenient for building the
program under one user name and installing it under another.

The commands should create all the directories in which files are to be
installed, if they don't already exist.  This includes the directories
specified as the values of the variables @code{prefix} and
@code{exec_prefix}, as well as all subdirectories that are needed.
One way to do this is by means of an @code{installdirs} target
as described below.

Use @samp{-} before any command for installing a man page, so that
@code{make} will ignore any errors.  This is in case there are systems
that don't have the Unix man page documentation system installed.

The way to install Info files is to copy them into @file{$(infodir)}
with @code{$(INSTALL_DATA)} (@pxref{Command Variables}), and then run
the @code{install-info} program if it is present.  @code{install-info}
is a program that edits the Info @file{dir} file to add or update the
menu entry for the given Info file; it is part of the Texinfo package.

Here is a sample rule to install an Info file that also tries to
handle some additional situations, such as @code{install-info} not
being present.

@comment This example has been carefully formatted for the Make manual.
@comment Please do not reformat it without talking to bug-make@gnu.org.
@smallexample
do-install-info: foo.info installdirs
        $(NORMAL_INSTALL)
# Prefer an info file in . to one in srcdir.
        if test -f foo.info; then d=.; \
         else d="$(srcdir)"; fi; \
        $(INSTALL_DATA) $$d/foo.info \
          "$(DESTDIR)$(infodir)/foo.info"
# Run install-info only if it exists.
# Use 'if' instead of just prepending '-' to the
# line so we notice real errors from install-info.
# Use '$(SHELL) -c' because some shells do not
# fail gracefully when there is an unknown command.
        $(POST_INSTALL)
        if $(SHELL) -c 'install-info --version' \
           >/dev/null 2>&1; then \
          install-info --dir-file="$(DESTDIR)$(infodir)/dir" \
                       "$(DESTDIR)$(infodir)/foo.info"; \
        else true; fi
@end smallexample

When writing the @code{install} target, you must classify all the
commands into three categories: normal ones, @dfn{pre-installation}
commands and @dfn{post-installation} commands.  @xref{Install Command
Categories}.

@item install-html
@itemx install-pdf
@itemx install-ps
These targets install documentation in formats other than Info;
they're intended to be called explicitly by the person installing the
package, if that format is desired.  GNU prefers Info files, so these
must be installed by the @code{install} target.

When you have many documentation files to install, we recommend that
you avoid collisions and clutter by arranging for these targets to
install in subdirectories of the appropriate installation directory,
such as @code{htmldir}.  As one example, if your package has multiple
manuals, and you wish to install HTML documentation with many files
(such as the ``split'' mode output by @code{makeinfo --html}), you'll
certainly want to use subdirectories, or two nodes with the same name
in different manuals will overwrite each other.

Please make these @code{install-@var{format}} targets invoke the
commands for the @var{format} target, for example, by making
@var{format} a dependency.

@item uninstall
Delete all the installed files---the copies that the @samp{install}
and @samp{install-*} targets create.

This rule should not modify the directories where compilation is done,
only the directories where files are installed.

The uninstallation commands are divided into three categories, just like
the installation commands.  @xref{Install Command Categories}.

@item install-strip
Like @code{install}, but strip the executable files while installing
them.  In simple cases, this target can use the @code{install} target in
a simple way:

@smallexample
install-strip:
        $(MAKE) INSTALL_PROGRAM='$(INSTALL_PROGRAM) -s' \
                install
@end smallexample

But if the package installs scripts as well as real executables, the
@code{install-strip} target can't just refer to the @code{install}
target; it has to strip the executables but not the scripts.

@code{install-strip} should not strip the executables in the build
directory which are being copied for installation.  It should only strip
the copies that are installed.

Normally we do not recommend stripping an executable unless you are sure
the program has no bugs.  However, it can be reasonable to install a
stripped executable for actual execution while saving the unstripped
executable elsewhere in case there is a bug.

@item clean
Delete all files in the current directory that are normally created by
building the program.  Also delete files in other directories if they
are created by this makefile.  However, don't delete the files that
record the configuration.  Also preserve files that could be made by
building, but normally aren't because the distribution comes with
them.  There is no need to delete parent directories that were created
with @samp{mkdir -p}, since they could have existed anyway.

Delete @file{.pdf} files here if they are not part of the distribution.

@item distclean
Delete all files in the current directory (or created by this
makefile) that are created by configuring or building the program.  If
you have unpacked the source and built the program without creating
any other files, @samp{make distclean} should leave only the files
that were in the distribution.  However, there is no need to delete
parent directories that were created with @samp{mkdir -p}, since they
could have existed anyway.

@item mostlyclean
Like @samp{clean}, but may refrain from deleting a few files that people
normally don't want to recompile.  For example, the @samp{mostlyclean}
target for GCC does not delete @file{libgcc.a}, because recompiling it
is rarely necessary and takes a lot of time.

@item maintainer-clean
Delete almost everything that can be reconstructed with this Makefile.
This typically includes everything deleted by @code{distclean}, plus
more: C source files produced by Bison, tags tables, Info files, and
so on.

The reason we say ``almost everything'' is that running the command
@samp{make maintainer-clean} should not delete @file{configure} even
if @file{configure} can be remade using a rule in the Makefile.  More
generally, @samp{make maintainer-clean} should not delete anything
that needs to exist in order to run @file{configure} and then begin to
build the program.  Also, there is no need to delete parent
directories that were created with @samp{mkdir -p}, since they could
have existed anyway.  These are the only exceptions;
@code{maintainer-clean} should delete everything else that can be
rebuilt.

The @samp{maintainer-clean} target is intended to be used by a maintainer of
the package, not by ordinary users.  You may need special tools to
reconstruct some of the files that @samp{make maintainer-clean} deletes.
Since these files are normally included in the distribution, we don't
take care to make them easy to reconstruct.  If you find you need to
unpack the full distribution again, don't blame us.

To help make users aware of this, the commands for the special
@code{maintainer-clean} target should start with these two:

@smallexample
@@echo 'This command is intended for maintainers to use; it'
@@echo 'deletes files that may need special tools to rebuild.'
@end smallexample

@item TAGS
Update a tags table for this program.
@c ADR: how?

@item info
Generate any Info files needed.  The best way to write the rules is as
follows:

@smallexample
info: foo.info

foo.info: foo.texi chap1.texi chap2.texi
        $(MAKEINFO) $(srcdir)/foo.texi
@end smallexample

@noindent
You must define the variable @code{MAKEINFO} in the Makefile.  It should
run the @code{makeinfo} program, which is part of the Texinfo
distribution.

Normally a GNU distribution comes with Info files, and that means the
Info files are present in the source directory.  Therefore, the Make
rule for an info file should update it in the source directory.  When
users build the package, ordinarily Make will not update the Info files
because they will already be up to date.

@item html
@itemx pdf
@itemx ps
Generate documentation files in the given format.  These targets
should always exist, but any or all can be a no-op if the given output
format cannot be generated.  These targets should not be dependencies
of the @code{all} target; the user must manually invoke them.

Here's an example rule for generating PDF files from Texinfo:

@smallexample
pdf: foo.pdf

foo.pdf: foo.texi chap1.texi chap2.texi
        $(TEXI2PDF) $(srcdir)/foo.texi
@end smallexample

@noindent
You must define the variable @code{TEXI2PDF} in the Makefile.  It
should run the program @code{texi2pdf}, which is part of the Texinfo
distribution.  (@code{texi2pdf} uses @TeX{} to do the real work of
formatting. @TeX{} is not distributed with Texinfo.)  Alternatively,
write only the dependencies, and allow GNU @code{make} to provide the
command.

Here's another example, this one for generating HTML from Texinfo:

@smallexample
html: foo.html

foo.html: foo.texi chap1.texi chap2.texi
        $(TEXI2HTML) $(srcdir)/foo.texi
@end smallexample

@noindent
Again, you would define the variable @code{TEXI2HTML} in the Makefile;
for example, it might run @code{makeinfo --no-split --html}
(@command{makeinfo} is part of the Texinfo distribution).

@item dist
Create a distribution tar file for this program.  The tar file should be
set up so that the file names in the tar file start with a subdirectory
name which is the name of the package it is a distribution for.  This
name can include the version number.

For example, the distribution tar file of GCC version 1.40 unpacks into
a subdirectory named @file{gcc-1.40}.

The easiest way to do this is to create a subdirectory appropriately
named, use @code{ln} or @code{cp} to install the proper files in it, and
then @code{tar} that subdirectory.

Compress the tar file with @code{gzip}.  For example, the actual
distribution file for GCC version 1.40 is called @file{gcc-1.40.tar.gz}.
It is ok to support other free compression formats as well.

The @code{dist} target should explicitly depend on all non-source files
that are in the distribution, to make sure they are up to date in the
distribution.
@ifset CODESTD
@xref{Releases, , Making Releases}.
@end ifset
@ifclear CODESTD
@xref{Releases, , Making Releases, standards, GNU Coding Standards}.
@end ifclear

@item check
Perform self-tests (if any).  The user must build the program before
running the tests, but need not install the program; you should write
the self-tests so that they work when the program is built but not
installed.
@end table

The following targets are suggested as conventional names, for programs
in which they are useful.

@table @code
@item installcheck
Perform installation tests (if any).  The user must build and install
the program before running the tests.  You should not assume that
@file{$(bindir)} is in the search path.

@item installdirs
It's useful to add a target named @samp{installdirs} to create the
directories where files are installed, and their parent directories.
There is a script called @file{mkinstalldirs} which is convenient for
this; you can find it in the Gnulib package.
You can use a rule like this:

@comment This has been carefully formatted to look decent in the Make manual.
@comment Please be sure not to make it extend any further to the right.--roland
@smallexample
# Make sure all installation directories (e.g. $(bindir))
# actually exist by making them if necessary.
installdirs: mkinstalldirs
        $(srcdir)/mkinstalldirs $(bindir) $(datadir) \
                                $(libdir) $(infodir) \
                                $(mandir)
@end smallexample

@noindent
or, if you wish to support @env{DESTDIR} (strongly encouraged),

@smallexample
# Make sure all installation directories (e.g. $(bindir))
# actually exist by making them if necessary.
installdirs: mkinstalldirs
        $(srcdir)/mkinstalldirs \
            $(DESTDIR)$(bindir) $(DESTDIR)$(datadir) \
            $(DESTDIR)$(libdir) $(DESTDIR)$(infodir) \
            $(DESTDIR)$(mandir)
@end smallexample

This rule should not modify the directories where compilation is done.
It should do nothing but create installation directories.
@end table

@node Install Command Categories
@section Install Command Categories

@cindex pre-installation commands
@cindex post-installation commands
When writing the @code{install} target, you must classify all the
commands into three categories: normal ones, @dfn{pre-installation}
commands and @dfn{post-installation} commands.

Normal commands move files into their proper places, and set their
modes.  They may not alter any files except the ones that come entirely
from the package they belong to.

Pre-installation and post-installation commands may alter other files;
in particular, they can edit global configuration files or data bases.

Pre-installation commands are typically executed before the normal
commands, and post-installation commands are typically run after the
normal commands.

The most common use for a post-installation command is to run
@code{install-info}.  This cannot be done with a normal command, since
it alters a file (the Info directory) which does not come entirely and
solely from the package being installed.  It is a post-installation
command because it needs to be done after the normal command which
installs the package's Info files.

Most programs don't need any pre-installation commands, but we have the
feature just in case it is needed.

To classify the commands in the @code{install} rule into these three
categories, insert @dfn{category lines} among them.  A category line
specifies the category for the commands that follow.

A category line consists of a tab and a reference to a special Make
variable, plus an optional comment at the end.  There are three
variables you can use, one for each category; the variable name
specifies the category.  Category lines are no-ops in ordinary execution
because these three Make variables are normally undefined (and you
@emph{should not} define them in the makefile).

Here are the three possible category lines, each with a comment that
explains what it means:

@smallexample
        $(PRE_INSTALL)     # @r{Pre-install commands follow.}
        $(POST_INSTALL)    # @r{Post-install commands follow.}
        $(NORMAL_INSTALL)  # @r{Normal commands follow.}
@end smallexample

If you don't use a category line at the beginning of the @code{install}
rule, all the commands are classified as normal until the first category
line.  If you don't use any category lines, all the commands are
classified as normal.

These are the category lines for @code{uninstall}:

@smallexample
        $(PRE_UNINSTALL)     # @r{Pre-uninstall commands follow.}
        $(POST_UNINSTALL)    # @r{Post-uninstall commands follow.}
        $(NORMAL_UNINSTALL)  # @r{Normal commands follow.}
@end smallexample

Typically, a pre-uninstall command would be used for deleting entries
from the Info directory.

If the @code{install} or @code{uninstall} target has any dependencies
which act as subroutines of installation, then you should start
@emph{each} dependency's commands with a category line, and start the
main target's commands with a category line also.  This way, you can
ensure that each command is placed in the right category regardless of
which of the dependencies actually run.

Pre-installation and post-installation commands should not run any
programs except for these:

@example
[ basename bash cat chgrp chmod chown cmp cp dd diff echo
expand expr false find getopt grep gunzip gzip
hostname install install-info kill ldconfig ln ls md5sum
mkdir mkfifo mknod mv printenv pwd rm rmdir sed sort tee
test touch true uname xargs yes
@end example

@cindex binary packages
The reason for distinguishing the commands in this way is for the sake
of making binary packages.  Typically a binary package contains all the
executables and other files that need to be installed, and has its own
method of installing them---so it does not need to run the normal
installation commands.  But installing the binary package does need to
execute the pre-installation and post-installation commands.

Programs to build binary packages work by extracting the
pre-installation and post-installation commands.  Here is one way of
extracting the pre-installation commands (the @option{-s} option to
@command{make} is needed to silence messages about entering
subdirectories):

@smallexample
make -s -n install -o all \
      PRE_INSTALL=pre-install \
      POST_INSTALL=post-install \
      NORMAL_INSTALL=normal-install \
  | gawk -f pre-install.awk
@end smallexample

@noindent
where the file @file{pre-install.awk} could contain this:

@smallexample
$0 ~ /^(normal-install|post-install)[ \t]*$/ @{on = 0@}
on @{print $0@}
$0 ~ /^pre-install[ \t]*$/ @{on = 1@}
@end smallexample