autoupdate.in

autoconf 2.59版,可用于redhat系统.用于编译原码,编写makefile文件.

      # -----------
      # Called at the end of all the obsolete macros.  Disable the
      # builtins, and m4sugar if needed..
      _au_define([_au_disable],
      [_au_popdef([_au_enabled])_au_dnl
      _au_ifdef([_au_enabled],
		[],
		[__au_disable()])])


      ## ------------------------------- ##
      ## Disable, and process the file.  ##
      ## ------------------------------- ##
      _au_divert(-1)
      # Disable m4: M4sugar and the AC autoquoting macros are not loaded yet,
      # hence invoking `_au_disable' is wrong.
      _au_include([unm4.m4])

      # Disable special characters.
      _au_changequote()
      _au_changecom()

      _au_divert(0)_au_dnl
EOF

    $input_m4 =~ s/^      //mg;

    # prepared input -- input, but reenables the quote before each AU macro.
    open INPUT_M4, ">$tmp/input.m4"
       or error "cannot open: $!";
    open FILE, "<$file"
       or error "cannot open: $!";
    print INPUT_M4 "$input_m4";
    while (<FILE>)
       {
	 eval $au_changequote;
	 print INPUT_M4;
       }
    close FILE
       or error "cannot close $file: $!";
    close INPUT_M4
       or error "cannot close $tmp/input.m4: $!";

    # Now ask m4 to perform the update.
    xsystem ("$m4 --include=$tmp"
	     . join (' --include=', '', reverse (@prepend_include))
	     . join (' --include=', '', @include)
	     . " $tmp/input.m4 >$tmp/updated");
    update_file ("$tmp/updated",
		 "$file" eq "$tmp/stdin" ? '-' : "$file");
  }
exit 0;


#		  ## ---------------------------- ##
#		  ## How `autoupdate' functions.  ##
#		  ## ---------------------------- ##
#
# The task of `autoupdate' is not trivial: the biggest difficulty being
# that you must limit the changes to the parts that really need to be
# updated.  Finding a satisfying implementation proved to be quite hard,
# as this is the fourth implementation of `autoupdate'.
#
# Below, we will use a simple example of obsolete macro:
#
#     AU_DEFUN([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))])
#     AC_DEFUN([NEW], [echo "sum($1) = $2"])
#
# the input file contains
#
#     dnl The Unbelievable Truth
#     OLD(1, 2)
#     NEW([0, 0], [0])
#
# Of course the expected output is
#
#     dnl The Unbelievable Truth
#     NEW([1, 2], [3])
#     NEW([0, 0], [0])
#
#
# # First implementation: sed
# # =========================
#
# The first implementation was only able to change the name of obsolete
# macros.
#
# The file `acoldnames.m4' defined the old names based on the new names.
# It was simple then to produce a sed script such as:
#
#     s/OLD/NEW/g
#
# Updating merely consisted in running this script on the file to
# update.
#
# This scheme suffers an obvious limitation: that `autoupdate' was
# unable to cope with new macros that just swap some of its arguments
# compared to the old macro.  Fortunately, that was enough to upgrade
# from Autoconf 1 to Autoconf 2.  (But I have no idea whether the
# changes in Autoconf 2 were precisely limited by this constraint.)
#
#
# # Second implementation: hooks
# # ============================
#
# The version 2.15 of Autoconf brought a vast number of changes compared
# to 2.13, so a solution was needed.  One could think to extend the
# `sed' scripts with specialized code for complex macros.  But this
# approach is of course full of flaws:
#
# a. the Autoconf maintainers have to write these snippets, which we
#    just don't want to,
#
# b. I really don't think you'll ever manage to handle the quoting of
#    m4 from sed.
#
# To satisfy a., let's remark that the code which implements the old
# features in term of the new feature is exactly the code which should
# replace the old code.
#
# To answer point b, as usual in the history of Autoconf, the answer, at
# least on the paper, is simple: m4 is the best tool to parse m4, so
# let's use m4.
#
# Therefore the specification is:
#
#     I want to be able to tell Autoconf, well, m4, that the macro I
#     am currently defining is an obsolete macro (so that the user is
#     warned), which code is the code to use when running autoconf,
#     but that the very same code has to be used when running
#     autoupdate.  To summarize, the interface I want is
#     `AU_DEFUN(OLD-NAME, NEW-CODE)'.
#
#
# Now for the technical details.
#
# When running autoconf, except for the warning, AU_DEFUN is basically
# AC_DEFUN.
#
# When running autoupdate, we want *only* OLD-NAMEs to be expanded.
# This obviously means that acgeneral.m4 and acspecific.m4 must not be
# loaded.  Nonetheless, because we want to use a rich set of m4
# features, m4sugar.m4 is needed.  Please note that the fact that
# Autoconf's macros are not loaded is positive on two points:
#
# - we do get an updated `configure.ac', not a `configure'!
#
# - the old macros are replaced by *calls* to the new-macros, not the
#   body of the new macros, since their body is not defined!!!
#   (Whoa, that's really beautiful!).
#
# Additionally we need to disable the quotes when reading the input for
# two reasons: first because otherwise `m4' will swallow the quotes of
# other macros:
#
#     NEW([1, 2], 3)
#     => NEW(1, 2, 3)
#
# and second, because we want to update the macro calls which are
# quoted, i.e., we want
#
#     FOO([OLD(1, 2)])
#     => FOO([NEW([1, 2], [3])])
#
# If we don't disable the quotes, only the macros called at the top
# level would be updated.
#
# So, let's disable the quotes.
#
# Well, not quite: m4sugar.m4 still needs to use quotes for some macros.
# Well, in this case, when running in autoupdate code, each macro first
# reestablishes the quotes, expands itself, and disables the quotes.
#
# Thinking a bit more, you realize that in fact, people may use `define'
# `ifelse' etc. in their files, and you certainly don't want to process
# them.  Another example is `dnl': you don't want to remove the
# comments.  You then realize you don't want exactly to import m4sugar:
# you want to specify when it is enabled (macros active), and disabled.
# m4sugar provides m4_disable/m4_enable to this end.
#
# You're getting close to it.  Now remains one task: how to handle
# twofold definitions?
#
# Remember that the same AU_DEFUN must be understood in two different
# ways, the AC way, and the AU way.
#
# One first solution is to check whether acgeneral.m4 was loaded.  But
# that's definitely not cute.  Another is simply to install `hooks',
# that is to say, to keep in some place m4 knows, late `define' to be
# triggered *only* in AU mode.
#
# You first think to design AU_DEFUN like this:
#
# 1. AC_DEFUN(OLD-NAME,
#	      [Warn the user OLD-NAME is obsolete.
#	       NEW-CODE])
#
# 2. Store for late AU binding([define(OLD_NAME,
#				[Reestablish the quotes.
#				 NEW-CODE
#				 Disable the quotes.])])
#
# but this will not work: NEW-CODE has probably $1, $2 etc. and these
# guys will be replaced with the argument of `Store for late AU binding'
# when you call it.
#
# I don't think there is a means to avoid this using this technology
# (remember that $1 etc. are *always* expanded in m4).  You may also try
# to replace them with $[1] to preserve them for a later evaluation, but
# if `Store for late AU binding' is properly written, it will remain
# quoted till the end...
#
# You have to change technology.  Since the problem is that `$1'
# etc. should be `consumed' right away, one solution is to define now a
# second macro, `AU_OLD-NAME', and to install a hook than binds OLD-NAME
# to AU_OLD-NAME.  Then, autoupdate.m4 just need to run the hooks.  By
# the way, the same method was used in autoheader.
#
#
# # Third implementation: m4 namespaces by m4sugar
# # ==============================================
#
# Actually, this implementation was just a clean up of the previous
# implementation: instead of defining hooks by hand, m4sugar was equipped
# with `namespaces'.  What are they?
#
# Sometimes we want to disable some *set* of macros, and restore them
# later.  We provide support for this via namespaces.
#
# There are basically three characters playing this scene: defining a
# macro in a namespace, disabling a namespace, and restoring a namespace
# (i.e., all the definitions it holds).
#
# Technically, to define a MACRO in NAMESPACE means to define the macro
# named `NAMESPACE::MACRO' to the VALUE.  At the same time, we append
# `undefine(NAME)' in the macro named `m4_disable(NAMESPACE)', and
# similarly a binding of NAME to the value of `NAMESPACE::MACRO' in
# `m4_enable(NAMESPACE)'.  These mechanisms allow to bind the macro of
# NAMESPACE and to unbind them at will.
#
# Of course this implementation is really inefficient: m4 has to grow
# strings which can become quickly huge, which slows it significantly.
#
# In particular one should avoid as much as possible to use `define' for
# temporaries.  Now that `define' as quite a complex meaning, it is an
# expensive operations that should be limited to macros.  Use
# `m4_define' for temporaries.
#
# Private copies of the macros we used in entering / exiting the m4sugar
# namespace.  It is much more convenient than fighting with the renamed
# version of define etc.
#
#
#
# Those two implementations suffered from serious problems:
#
# - namespaces were really expensive, and incurred a major performance
#   loss on `autoconf' itself, not only `autoupdate'.  One solution
#   would have been the limit the use of namespaces to `autoupdate', but
#   that's again some complications on m4sugar, which really doesn't need
#   this.  So we wanted to get rid of the namespaces.
#
# - since the quotes were disabled, autoupdate was sometimes making
#   wrong guesses, for instance on:
#
#     foo([1, 2])
#
#   m4 saw 2 arguments: `[1'and `2]'.  A simple solution, somewhat
#   fragile, is to reestablish the quotes right before all the obsolete
#   macros, i.e., to use sed so that the previous text becomes
#
#     changequote([, ])foo([1, 2])
#
#   To this end, one wants to trace the definition of obsolete macros.
#
# It was there that the limitations of the namespace approach became
# painful: because it was a complex machinery playing a lot with the
# builtins of m4 (hence, quite fragile), tracing was almost impossible.
#
#
# So this approach was dropped.
#
#
# # The fourth implementation: two steps
# # ====================================
#
# If you drop the uses of namespaces, you no longer can compute the
# updated value, and replace the old call with it simultaneously.
#
# Obviously you will use m4 to compute the updated values, but you may
# use some other tool to achieve the replacement.  Personally, I trust
# nobody but m4 to parse m4, so below, m4 will perform the two tasks.
#
# How can m4 be used to replace *some* macros calls with newer values.
# Well, that's dead simple: m4 should learn the definitions of obsolete
# macros, forget its builtins, disable the quotes, and then run on the
# input file, which amounts to doing this:
#
#     divert(-1)dnl
#     changequote([, ])
#     define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
#     undefine([dnl])
#     undefine([m4_eval])
#     # Some more undefines...
#     changequote()
#     divert(0)dnl
#     dnl The Unbelievable Truth
#     changequote([, ])OLD(1, 2)
#     NEW([0, 0],
#	  0)
#
# which will result in
#
#     dnl The Unbelievable Truth
#     NEW(1, 2, m4_eval(1 + 2))
#     NEW([0, 0],
#	  0)
#
# Grpmh.  Two problems.  A minor problem: it would have been much better
# to have the `m4_eval' computed, and a major problem: you lost the
# quotation in the result.
#
# Let's address the big problem first.  One solution is to define any
# modern macro to rewrite its calls with the proper quotation, thanks to
# `$@'.  Again, tracing the `define's makes it possible to know which
# are these macros, so you input is:
#
#     divert(-1)dnl
#     changequote([, ])
#     define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
#     define([NEW], [[NEW($@)]changequote()])
#     undefine([dnl])
#     undefine([m4_eval])
#     # Some more undefines...
#     changequote()
#     divert(0)dnl
#     dnl The Unbelievable Truth
#     changequote([, ])OLD(1, 2)
#     changequote([, ])NEW([0, 0],
#	  0)
#
# which results in
#
#     dnl The Unbelievable Truth
#     NEW([1, 2],[m4_eval(1 + 2)])
#     NEW([0, 0],[0])
#
# Our problem is solved, i.e., the first call to `NEW' is properly
# quoted, but introduced another problem: we changed the layout of the
# second calls, which can be a drama in the case of huge macro calls
# (think of `AC_TRY_RUN' for instance).  This example didn't show it,
# but we also introduced parens to macros which did not have some:
#
#     AC_INIT
#     => AC_INIT()