autoconf/TODO

-*- outline -*-

Things it might be nice to do someday.  I haven't evaluated all of
these suggestions... their presence here doesn't imply my endorsement.
-djm

------------------------------------------------------------------------------

* 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.

------------------------------------------------------------------------------

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

------------------------------------------------------------------------------

* Use AC_EGREP_CPP instead of AC_TRY_LINK to detect structures and members.

------------------------------------------------------------------------------

* Make AC_CHECK_FUNC[S] automatically use any particular macros for the
  listed functions.

------------------------------------------------------------------------------

* Support creating both config.h and DEFS in the same configure.

------------------------------------------------------------------------------

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

------------------------------------------------------------------------------

* Doc: Add a concept index.

------------------------------------------------------------------------------

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

------------------------------------------------------------------------------

* Split up AC_SUBST substitutions using a loop to accomodate shells
  with severely limited here document sizes, if it turns out to be a problem.
  I'm not sure whether the limit is on lines or bytes; if bytes, it
  will be less of a problem than it was with the long lines used for
  creating a header file.

------------------------------------------------------------------------------

* Allow [ and ] in AC_DEFINE args.

------------------------------------------------------------------------------

* 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.

------------------------------------------------------------------------------

* autoscan: Tell the files that caused inclusion of each macro,
in a dnl comment.  (Seems to be hard.)

------------------------------------------------------------------------------

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

------------------------------------------------------------------------------

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)

------------------------------------------------------------------------------

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

------------------------------------------------------------------------------

Have AC_CANONICAL_* cache the host/build/target types.
They have to be overridden by the command line arguments,
just as for X includes and libraries.  Should they be cached
all in one variable, or three?  In that case, what if only one
or two of the cache variables are set?

------------------------------------------------------------------------------

     The argument HELP-STRING is a description of the option which
     ...
     Avoid tabs in the help string.  You'll need to enclose it in `['
     and `]' in order to produce the leading spaces.

Except that [...] is the convention for telling the user the default,
So I guess a changequote(`,') or something would be in order in some cases.
From: "K. Berry" <kb@cs.umb.edu>

------------------------------------------------------------------------------

The default of unlimited permission is fine, but there should be some easy
way for configure to have copyright terms passed through from configure.in.
Maybe AC_LICENSE([...]).
From: roland@gnu.ai.mit.edu (Roland McGrath)

------------------------------------------------------------------------------

AC_MSG_CHECKING([checking for ANSI #stringize])
AC_REVISION([ #(@) revision 2.1 ])

causes bogus code to be generated for whatever immediately follows.  The
problem goes away if the '#' is removed.  Probably the macros are not
disabling the m4 "comment" feature when processing user-supplied strings.
-Jim Avera jima@netcom.com

------------------------------------------------------------------------------

on hal.gnu.ai.mit.edu, configure is getting the wrong answer for
AC_CHECK_FUNCS(select).

The problem here is that there's severe namespace pollution: when
conftest.c includes <ctype.h> to pick up any __stub macro definitions,
it's getting a prototype declaration for select(), which collides
with the dummy declaration in conftest.c.  (The chain of includes
is conftest.c -> <ctype.h> -> <sys/localedef.h> -> <sys/lc_core.h>
-> <sys/types.h> -> <sys/select.h>.)

	#define $ac_func __dummy_$ac_func
	#include <ctype.h>
	#undef $ac_func
From: kwzh@gnu.ai.mit.edu (Karl Heuer)

The test for the isascii function was failing because that function is
also a macro.  He proposed that the test file look like this:

/* Remove any macro definition. */
#undef isascii
/* Override any gcc2 internal prototype to avoid an error.  */
char isascii(); isascii();

Andreas Schwab

------------------------------------------------------------------------------

put all the config.* stuff somewhere like config/?
All these extraneous files sure clutter up a toplevel directory.
From: "Randall S. Winchester" <rsw@eng.umd.edu>

------------------------------------------------------------------------------

It would be nice if I could (in the Makefile.in files) set
the path to 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" <rsw@eng.umd.edu>

------------------------------------------------------------------------------

In libc and make in aclocal.m4 I have AC_CHECK_SYMBOL, which checks for
sys_siglist et al.  Using AC_CHECK_FUNC doesn't work on some system that
winds up caring that you reference it as a function and it is really a
variable.  My version always declares the symbol as a char *[]; if that
ends up a bad idea, we can have it take an arg with the C decl, but that is
a bit verbose to write if it's actually superfluous.
From Roland McGrath.
[I'd call it AC_CHECK_VAR, I think. -djm]

------------------------------------------------------------------------------

In a future version (after 2.2), make AC_PROG_{CC,RANLIB,anything else}
use AC_CHECK_TOOL.
From Roland McGrath.

------------------------------------------------------------------------------

	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_ <eichin@cygnus.com>

------------------------------------------------------------------------------

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 apropriate checks, the existance of the paths, 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 paths to check for stuff ($PKG-ROOT/lib for 
example)
From: Randall Winchester

------------------------------------------------------------------------------

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_PROGRAMS_CHECK(AR_FOR_TARGET, $target-ar, $target-ar, ar)
AC_PROGRAMS_CHECK(RANLIB_FOR_TARGET, $target-ranlib, $target-ranlib, ranlib)
AC_PROGRAMS_CHECK(GCC_FOR_TARGET, $target-gcc, $target-gcc, gcc)
fi

This could be improved to also look for gcc in PATH, but require the
prefix to contain the target e.g.:

target=m68k-coff -->GCC_FOR_TARGET = /usr/gnu/m68k-coff/bin/gcc

From: nennker@cs.tu-berlin.DE (Axel Nennker)

------------------------------------------------------------------------------

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.

------------------------------------------------------------------------------

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

------------------------------------------------------------------------------

* Test suite: more things to test:
** That the shell scripts produce correct output on some simple data.
** Configuration header files.  That autoheader does the right thing,
   and so does AC_CONFIG_HEADER when autoconf is run.

------------------------------------------------------------------------------

Autoheader in autoconf-2.4 doesn't produce entries for:

        AC_CHECK_TYPE(ssize_t, int)

and it seems like it could easily do so.

In general, it seems to me like autoconf isn't set up to
let me periodically run autoheader, and then include my
"local" tests -- autoheader gets most stuff right, I'd like
to rerun it periodically without losing my local changes
to config.h.in.

One of the things that I need is to know is the type to use
for a fixed size on disk, e.g., what is the system's name
for an unsigned-32-bit integer?

I can use:

        AC_CHECK_SIZEOF(unsigned int)

and, in fact, that's what I do.  But I still have to build
sets of #if tests to get from there to the name of the type.

From:    bostic@bsdi.com (Keith Bostic)

------------------------------------------------------------------------------

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 <rsalz@osf.org>

------------------------------------------------------------------------------

It is IMHO a bug that `config.status' cannot handle multiple
simultaneous invocations.  It should include the process id (`$$' in sh)
as part of the name of any temporary files it creates.

From:    fjh@kryten.cs.mu.oz.au (Fergus Henderson)

------------------------------------------------------------------------------

Timezone calculations checks.

------------------------------------------------------------------------------

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

------------------------------------------------------------------------------

Mention automake, libtool, etc. in the autoconf manual.

------------------------------------------------------------------------------

I wonder if it is possible to get the path for 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 <eserte@cabulja.herceg.de>

------------------------------------------------------------------------------

Question: at least one common UNIX variant has a "cc" that is old K&R
and "c89" for ANSI C.  Is there any reason why AC_PROG_CC couldn't
check for c89 before cc if it can't find gcc?

hpa@yggdrasil.com (H. Peter Anvin)

------------------------------------------------------------------------------

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: roland@gnu.ai.mit.edu (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: friedman@splode.com (Noah Friedman)

------------------------------------------------------------------------------

So how about an option to configure --reset-cache, that says to ignore all
existing cached values for tests that configure runs, and then update the
cache normally.  This should be utterly trivial to do in AC_CACHE_VAL;
check the flag variable and always compute the value if it's set.

------------------------------------------------------------------------------

A number of people have tried to fix configuration problems by editing
acconfig.h. (Despite comments at the top of the file.) I think they're
confused because anything.h looks like a regular source file name.
Maybe acconfig.h could be called acconfig.extra or something?

From: kb@cs.umb.edu (K. Berry)

------------------------------------------------------------------------------

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: rcb5@win.tue.nl (Richard Verhoeven)

------------------------------------------------------------------------------

When using CONFIG_FILES= and CONFIG_HEADERS= for controlling
partial configuration, any AC_LINK_FILES is repeated in each case
(that is, usually, once for config.h and once per subdirectory).
This is not elegant.

Maybe Autoconf could use some kind of CONFIG_LINKS=<file-list>,
having all such AC_LINK(ed)_FILES by default, but usable by each
Makefile.in in rules for updating the particular links they need.

From: pinard@iro.umontreal.ca

------------------------------------------------------------------------------

Perhaps autoconf could have a single @magic@ frob that gets replaced with
assignments for all the *dir variables?  There is quite a plethora for each
Makefile.in to have foodir = @foodir@.

From: Roland McGrath <roland@gnu.ai.mit.edu>

------------------------------------------------------------------------------

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: pinard@iro.umontreal.ca

------------------------------------------------------------------------------

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

Rick Boykin <rboykin@cscsun3.larc.nasa.gov>

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

------------------------------------------------------------------------------

    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 supresses the "checking for...result"
    messages, not the "creating FOO" messages.

I think the default should be to suppress both.
From: Richard Stallman <rms@gnu.ai.mit.edu>

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 <roland@gnu.ai.mit.edu>

------------------------------------------------------------------------------

Use automake to generate autoconf's Makefile.in's?

------------------------------------------------------------------------------

about the idea of using small configure.in/aclocal.m4 snippets:
this is the one idea in metaconfig (the autoconf-like program used by
Perl) that I like.  metaconfig looks for a "U" directory, and includes
each ".U" file into the generated Configure script (according to
various complicated rules).
From: Tom Tromey <tromey@creche.cygnus.com>

------------------------------------------------------------------------------

I'd much prefer to see the absolute paths substituted for all the
standard "dir" variables.  It would be nice to have variables in
configure that held the absolute paths.  And it is nice to be able to
substitute them into other files without relying on the destination
file supporting ${...}  syntax.  (It works in Perl, sh, and make --
but not guile)

From: Tom Tromey <tromey@creche.cygnus.com>

------------------------------------------------------------------------------

Another thing I wish for is a macro which figures out which libraries are 
needed for BSD-sytle sockets.  AC_PATH_X already detects this 
correctly...so it's just a matter of seperating out the socket-related code.
From: "Joel N. Weber II" <nemo@koa.iolani.honolulu.hi.us>

------------------------------------------------------------------------------

Merge the two lex macros, AC_PROG_LEX and AC_DECL_YYTEXT?

------------------------------------------------------------------------------

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: jimb@totoro.bio.indiana.edu (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: bostic@bsdi.com (Keith Bostic)

------------------------------------------------------------------------------

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.

------------------------------------------------------------------------------

there is absolutely no guarantee that 'a' to 'z' are
contiguous, and the ISLOWER macro is not guaranteed to correctly
reproduce the result of islower. In all variants of ASCII however, it
will work correctly in the C locale.

There is also no guarantee that toupper(i) - i is the same constant if
non-zero. TOUPPER, hence, is not correct either. But, in all variants
of ASCII in the C locale, it works.

Tanmoy Bhattacharya (tanmoy@qcd.lanl.gov>

------------------------------------------------------------------------------

autoreconf doesn't support having (in the same tree) both directories
that are parts of a larger package (sharing aclocal.m4 and acconfig.h),
and directories that are independent packages (each with their own ac*).
It assumes that they are all part of the same package, if you use --localdir,
or that each directory is a separate package, if you don't use it.

autoreconf should automatically figure out which ac* files to use--the
closest ones up the tree from each directory, probably, unless
overridden by --localdir.

Also, autoreconf recurses on all subdirectories containing a
configure.in, not just those given by an AC_CONFIG_SUBDIRS directive.
This may not be a problem in practice.

------------------------------------------------------------------------------