todo

autoconf是一个产生可以自动配置源代码包

AS_CHECK_HEADER will still be used.  Conversely, some headers may not
require a specific AC_ tests, but a specialized AS_ macro.

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* Make AC_CHECK_LIB check whether the function is already available
  before checking for the library.  This might involve adding another
  kind of cache variable to indicate whether a given function needs a
  given library.  The current ac_cv_func_ variables are intended to
  indicate whether the function is in the default libraries, but
  actually also take into account whatever value LIBS had when they
  were checked for.

  Isn't this the issue of AC_SEARCH_LIB? --akim
  How come the list of libraries to browse not an additional parameter
  of AC_CHECK_FUNC, exactly like for the headers? --akim

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* Add AC_PROG_CC_POSIX to replace the current ad-hoc macros for AIX,
  Minix, ISC, etc.

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* Select the right CONFIG_SHELL automatically (for Ultrix, Lynx especially.)

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* Doc: Centralize information on POSIX, MS-DOS, cross-compiling, and
  other important topics.

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* Mike Haertel's suggestions:

** Provide header files containing decls for alloca, strings, etc.

** Cross compiling:

*** Error messages include instructions for overriding defaults using
config.site.

*** Distribute a config.site corresponding to a hypothetical bare POSIX system with c89.

** Site defaults:

*** Convention for consistency checking of env vars and options in config.site so config.site can print obnoxious messages if it doesn't like options or env vars that users use.

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* Look at user contributed macros:
	IEEE double precision math
	more

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* Provide a way to create a config.h *and* set the DEFS variable from within
the same configure script.

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For AC_TYPE_SIGNAL signal handlers, provide a way for code to know
whether to do "return 0" or "return" (int vs void) to avoid compiler
warnings.  (Roland McGrath)

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In config.status comment, put the host/target/build types, if used.

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It would be nice if I could (in the Makefile.in files) set the
relative name of config.h. You have config.h ../config.h
../../config.h's all over the place, in the findutils-4.1 directory.
From: "Randall S. Winchester" <[e-mail]>

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	ls -lt configure configure.in | sort
doesn't work right if configure.in is from a symlink farm, where the
symlink has either a timestamp of its own, or under BSD 4.4, it has
the timestamp of the current directory, neither of which
helps. Changing it to
	ls -Llt configure configure.in | sort
works for me, though I don't know how portable that is
_Mark_ <[e-mail]>

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Here is the thing I would like the most;
AC_PKG_WITH(PACKAGE, HELP_STRING, PACKAGE-ROOT, PACKAGE-LIBS, PACKAGE-DEFS,
	PACKAGE-CCPFLAGS)
like

AC_PKG_WITH(kerberos,,/usr/local/athena,-lkrb -ldes,[KERBEROS KRB4
CRYPT],include)
AC_PKG_WITH(hesiod,
[if hesiod is not in kerberos-root add --with-hesiod-root=somewhere]
,,-lhesiod,HESIOD,,)
AC_PKG_WITH(glue,,,-lglue,GLUE,,)
AC_PKG_WITH(bind,,/usr/local/bind, [lib/resolv.a lib/lib44bsd.a], ,include)
After the appropriate checks, the existence of the files, and libs and such
LIBS=$LIBS $PKG-LIBS
DEFS=$DEFS $PKG-DEFS
CPPFLAGS=$PKG-CPPFLAGS $CPPFLAGS
$PKG-ROOT=$PKG-ROOT
The cppflags should reverse the order so that you can have;
-I/usr/local/bind/include -I/usr/local/athena/include
and
-L/usr/local/athena/lib -lkrb -ldes /usr/local/bind/lib/libresolv.a
as order matters.

also an AC_PKG_CHK_HEADER
and an AC_PKG_CHK_FUNCTION
so one can give alternate names to check for stuff ($PKG-ROOT/lib for
example)
From: Randall Winchester

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AC_C_CROSS assumes that configure was called like 'CC=target-gcc;
./configure'. I want to write a package that has target dependent
libraries and host dependent tools. So I don't like to lose the
distinction between CC and [G]CC_FOR_TARGET.  AC_C_CROSS should check
for equality of target and host.

It would be great if

GCC_FOR_TARGET
AR_FOR_TARGET
RANLIB_FOR_TARGET

would be set automatically if host != target.
AC_LANG_CROSS_C would be nice too, to check header files
etc. with GCC_FOR_TARGET instead of CC

Here is one simple test

if test "x$host" != "x$target"; then
AC_CHECK_PROGS(AR_FOR_TARGET,
	       [$target-ar, $prefix/$target/bin/ar], $target-ar)
AC_CHECK_PROGS(RANLIB_FOR_TARGET, $target-ranlib, $target-ranlib)
	       [$target-ranlib, $prefix/$target/bin/ranlib], $target-ranlib)
AC_CHECK_PROGS(GCC_FOR_TARGET, $target-gcc, $target-gcc)
	       [$target-gcc, $prefix/$target/bin/gcc], $target-gcc)
fi

From: [e-mail] (Axel Nennker)

(also look in the autoconf mailing list archives for the proposed
CHECK_TARGET_TOOL macro from Natanael Nerode, a gcc configury guru).

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The problem occurs with the following libc functions in SunOS 5.4:

	fnmatch glob globfree regcomp regexec regerror regfree wordexp wordfree

It also occurs with a bunch more libposix4 functions that most people
probably aren't worried about yet, e.g. shm_open.

All these functions fail with errno set to ENOSYS (89)
``Operation not applicable''.

Perhaps Autoconf should have a specific macro for fnmatch, another for
glob+globfree, another for regcomp+regexec+regerror+regfree, and
another for wordexp+wordfree.  This wouldn't solve the problem in
general, but it should work for Solaris 2.4.  Or Autoconf could limit
itself to fnmatch and regcomp, the only two functions that I know have
been a problem so far.

From Paul Eggert.

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Make easy macros for checking for X functions and libraries, such as Motif.

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There are basically three ways to lock files
        lockf, fnctl, flock
I'd be interested in adding a macro to pick the "right one" if you're
interested.

From:    Rich Salz <[e-mail]>

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Timezone calculations checks.

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Support different default file system layouts, e.g. SVR4, Linux.
Of course, this can be done locally with config.site.

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I wonder if it is possible to get the name of X11's app-defaults
directory by autoconf. Moreover, I'd like to have a general way of
accessing imake variables by autoconf, something like

AC_DEFINE(WINE_APP_DEFAULTS, AC_IMAKE_VAR(XAPPLOADDIR))

Slaven Rezic <[e-mail]>

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Cache consistency checking: ignore cache if environment
(CC or PATH) differs.
From Mike Haertel

So we need a general mechanism for storing variables' values in the cache,
and checking if they are the same after reading the cache.  Then we can add
to the list of variables as we come across the need.  So far we want
LD_LIBRARY_PATH and the internal variables for some of (all?) the args.
From: [e-mail] (Roland McGrath)

Hmm.  That list might include LD_LIBRARY_PATH, LD_RUN_PATH (for solaris),
and PATH.  I can't think of any others so far.
From: [e-mail] (Noah Friedman)

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Every user running X11 usually has a directory like *X11* in his PATH
variable. By replacing bin by include, you can find good places to
look for the include files or libraries.

From: [e-mail] (Richard Verhoeven)

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In most cases, when autoscan suggests something, using the search or
index command into the Info reader for autoconf manual quickly
explains me what the test is about.  However, for header files and
functions, the search might fail, because the test is not of the
specific kind.  The Autoconf manual should reflect somewhere all
header files or functions (non-specific features, generally)
triggering autoscan to generate tests, and tell in a few words what is
the problem, and the suggested approach for a solution; that is, how
one should use the result of testing the feature.

From: [e-mail]

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It would be nice if the configure script would handle an option such as
--x-libraries="/usr/openwin/lib /usr/dt/lib".

Rick Boykin <[e-mail]>

Under Solaris 2.4, the regular X includes and libs and the Motif
includes and libs are in different places.  The Emacs configure script
actually allows dir1:dir2:dir3 --

    if test "${x_libraries}" != NONE && test -n "${x_libraries}"; then
      LD_SWITCH_X_SITE=-L`echo ${x_libraries} | sed -e "s/:/ -L/g"`
      LD_SWITCH_X_SITE_AUX=-R`echo ${x_libraries} | sed -e "s/:/ -R/g"`
    fi
    if test "${x_includes}" != NONE && test -n "${x_includes}"; then
      C_SWITCH_X_SITE=-I`echo ${x_includes} | sed -e "s/:/ -I/g"`
    fi

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    What messages should be produced by default, if any?

Probably only the few most important ones, like which configuration
name was used, whether X or Xt are in use, etc. The specific
decisions, and progress messages, should be recorded on the terminal
only if --verbose is used.

    --silent just suppresses the "checking for...result"
    messages, not the "creating FOO" messages.

I think the default should be to suppress both.
From: Richard Stallman <[e-mail]>

There is no distinction now between
important decisions (we have X) vs minor decisions (we have lstat).
However, there are probably only a few things you deem important enough to
announce and only those few things will need to be changed.
Perhaps config.status could be written with comments saying what was
decided.
From: Roland McGrath <[e-mail]>

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Another thing I wish for is a macro which figures out which libraries are
needed for BSD-style sockets.  AC_PATH_X already detects this
correctly...so it's just a matter of separating out the socket-related code.
From: "Joel N. Weber II" <[e-mail]>

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in order to use the AC_CANONICAL_SYSTEM macro, I have to have
install-sh somewhere nearby --- why is this?  I have no real reason to
distribute install-sh, other than that its absence breaks this code.

Shouldn't the above loop be looking for config.sub and config.guess?
From: [e-mail] (Jim Blandy)

adding AC_CANONICAL_HOST to my configure.in script caused
all sorts of odd/unexplained errors.  Obviously, I had to go
get copies of config.guess, config.sub and install-sh from the
autoconf distribution, but the error messages and autoconf docs
didn't explain that very well.
From: [e-mail] (Keith Bostic)

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Perhaps also have AC_TRY_COMPILER try to link an invalid program, and
die if the compiler seemed to succeed--in which case it's not usable
with autoconf scripts.

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