todo

这是一个自动生成MAKEFILE的工具。在LINUX工程项目里是很好的帮手。希望对大家有点帮助。

-*- 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

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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.

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

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

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

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

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* Doc: Add a concept index.

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

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* 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.

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* Allow [ and ] in AC_DEFINE args.

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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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* 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

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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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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?

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     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" <[e-mail]>

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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: [e-mail] (Roland McGrath)

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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 [e-mail]

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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: [e-mail] (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

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put all the config.* stuff somewhere like config/?
All these extraneous files sure clutter up a toplevel directory.
From: "Randall S. Winchester" <[e-mail]>

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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" <[e-mail]>

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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]

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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_ <[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 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: [e-mail] (Axel Nennker)

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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.