Re: present but cannot be compiled (Was: Building linc CVS)

[Akim Demaille]

Thanks for the bug report!

Contrary to the message reported by ./configure, this is not a bug in
Autoconf, but the result of a recent incompatible change in Autoconf
that is likely to require the package's configure.ac to be updated.
Please, first make sure you are trying the most recent version of that
package, then, if you are, send all this message (including your
output attached) to the bug list (or the authors) of the package you
were trying to configure.

Below two parts of the Autoconf documentation are included: 1. the
documentation of AC_CHECK_HEADER(S), and 2. what's to be done to
upgrade configure.ac.

If you have some knowledge in C compilation, then there is something
more you can do to help: find out what are the prerequisite headers on
your system.

For instance, if the error message is:

       sys/socket.h: present but cannot be compiled
       sys/socket.h: check for missing prerequisite headers?
       sys/socket.h: proceeding with the preprocessor's result

then try to compile the program sample.c:

       #include <sys/socket.h>

with `cc -c sample.c'.  It will fail.  Then try to understand what
other headers are needed.  For instance, on Darwin, one needs:

       #include <stdio.h>
       #include <stdlib.h>
       #include <sys/socket.h>
       #include <sys/socket.h>

to get a successful compilation.  Then, send this additional
information to the package maintainers, together with a description of
your machine.

Thanks!

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

Generic Header Checks
---------------------

   These macros are used to find system header files not covered by the
"particular" test macros.  If you need to check the contents of a header
as well as find out whether it is present, you have to write your own
test for it (*note Writing Tests::).

 - Macro: AC_CHECK_HEADER (HEADER-FILE, [ACTION-IF-FOUND],
          [ACTION-IF-NOT-FOUND], [INCLUDES = `default-includes'])
     If the system header file HEADER-FILE is compilable, execute shell
     commands ACTION-IF-FOUND, otherwise execute ACTION-IF-NOT-FOUND.
     If you just want to define a symbol if the header file is
     available, consider using `AC_CHECK_HEADERS' instead.

     For compatibility issues with older versions of Autoconf, please
     read below.

 - Macro: AC_CHECK_HEADERS (HEADER-FILE..., [ACTION-IF-FOUND],
          [ACTION-IF-NOT-FOUND], [INCLUDES = `default-includes'])
     For each given system header file HEADER-FILE in the
     whitespace-separated argument list that exists, define
     `HAVE_HEADER-FILE' (in all capitals).  If ACTION-IF-FOUND is
     given, it is additional shell code to execute when one of the
     header files is found.  You can give it a value of `break' to
     break out of the loop on the first match.  If ACTION-IF-NOT-FOUND
     is given, it is executed when one of the header files is not found.

     For compatibility issues with older versions of Autoconf, please
     read below.

   Previous versions of Autoconf merely checked whether the header was
accepted by the preprocessor.  This was changed because the old test was
inappropriate for typical uses.  Headers are typically used to compile,
not merely to preprocess, and the old behavior sometimes accepted
headers that clashed at compile-time.  If you need to check whether a
header is preprocessable, you can use `AC_PREPROC_IFELSE' (*note
Running the Preprocessor::).

   This scheme, which improves the robustness of the test, also requires
that you make sure that headers that must be included before the
HEADER-FILE be part of the INCLUDES, (*note Default Includes::).  If
looking for `bar.h', which requires that `foo.h' be included before if
it exists, we suggest the following scheme:


AC_CHECK_HEADERS([foo.h])
AC_CHECK_HEADERS([bar.h], [], [],
[#if HAVE_FOO_H
# include <foo.h>
# endif
])

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

Header Present But Cannot Be Compiled
=====================================

   The most important guideline to bear in mind when checking for
features is to mimic as much as possible the intended use.
Unfortunately, old versions of `AC_CHECK_HEADER' and `AC_CHECK_HEADERS'
failed to follow this idea, and called the preprocessor, instead of the
compiler, to check for headers.  As a result, incompatibilities between
headers went unnoticed during configuration, and maintainers finally
had to deal with this issue elsewhere.

   As of Autoconf 2.56 both checks are performed, and `configure'
complains loudly if the compiler and the preprocessor do not agree.
For the time being the result used is that of the preprocessor, to give
maintainers time to adjust their `configure.ac', but in the near
future, only the compiler will be considered.

   Consider the following example:

     $ cat number.h
     typedef int number;
     $ cat pi.h
     const number pi = 3;
     $ cat configure.ac
     AC_INIT
     AC_CHECK_HEADERS(pi.h)
     $ autoconf -Wall
     $ ./configure
     checking for gcc... gcc
     checking for C compiler default output... a.out
     checking whether the C compiler works... yes
     checking whether we are cross compiling... no
     checking for suffix of executables...
     checking for suffix of object files... o
     checking whether we are using the GNU C compiler... yes
     checking whether gcc accepts -g... yes
     checking for gcc option to accept ANSI C... none needed
     checking how to run the C preprocessor... gcc -E
     checking for egrep... grep -E
     checking for ANSI C header files... yes
     checking for sys/types.h... yes
     checking for sys/stat.h... yes
     checking for stdlib.h... yes
     checking for string.h... yes
     checking for memory.h... yes
     checking for strings.h... yes
     checking for inttypes.h... yes
     checking for stdint.h... yes
     checking for unistd.h... yes
     checking pi.h usability... no
     checking pi.h presence... yes
     configure: WARNING: pi.h: present but cannot be compiled
     configure: WARNING: pi.h: check for missing prerequisite headers?
     configure: WARNING: pi.h: proceeding with the preprocessor's result
     configure: WARNING:     ## ------------------------------------ ##
     configure: WARNING:     ## Report this to address@hidden ##
     configure: WARNING:     ## ------------------------------------ ##
     checking for pi.h... yes

The proper way the handle this case is using the fourth argument (*note
Generic Headers::):

     $ cat configure.ac
     AC_INIT
     AC_CHECK_HEADERS(number.h pi.h,,,
     [[#if HAVE_NUMBER_H
     # include <number.h>
     #endif
     ]])
     $ autoconf -Wall
     $ ./configure
     checking for gcc... gcc
     checking for C compiler default output... a.out
     checking whether the C compiler works... yes
     checking whether we are cross compiling... no
     checking for suffix of executables...
     checking for suffix of object files... o
     checking whether we are using the GNU C compiler... yes
     checking whether gcc accepts -g... yes
     checking for gcc option to accept ANSI C... none needed
     checking for number.h... yes
     checking for pi.h... yes

   See *Note Particular Headers::, for a list of headers with their
prerequisite.

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

Portability of Headers
----------------------

This section tries to collect knowledge about common headers, and the
problems they cause.  By definition, this list will always require
additions.  Please help us keeping it as complete as possible.

`inttypes.h' vs. `stdint.h'
     Paul Eggert notes that: ISO C 1999 says that `inttypes.h' includes
     `stdint.h', so there's no need to include `stdint.h' separately in
     a standard environment.  Many implementations have `inttypes.h'
     but not `stdint.h' (e.g., Solaris 7), but I don't know of any
     implementation that has `stdint.h' but not `inttypes.h'.  Nor do I
     know of any free software that includes `stdint.h'; `stdint.h'
     seems to be a creation of the committee.

`linux/irda.h'
     It requires `linux/types.h' and `sys/socket.h'.

`net/if.h'
     On Darwin, this file requires that `sys/socket.h' be included
     beforehand.  One should run:

          AC_CHECK_HEADERS([sys/socket.h])
          AC_CHECK_HEADERS([net/if.h], [], [],
          [#include <stdio.h>
          #if STDC_HEADERS
          # include <stdlib.h>
          # include <stddef.h>
          #else
          # if HAVE_STDLIB_H
          #  include <stdlib.h>
          # endif
          #endif
          #if HAVE_SYS_SOCKET_H
          # include <sys/socket.h>
          #endif
          ])

`stdint.h'
     See above, item `inttypes.h' vs. `stdint.h'.

`stdlib.h'
     On many systems (e.g., Darwin), `stdio.h' is a prerequisite.

`sys/socket.h'
     On Darwin, `stdlib.h' is a prerequisite.

`X11/extensions/scrnsaver.h'
     Using XFree86, this header requires `X11/Xlib.h', which is probably
     so required that you might not even consider looking for it.

          AC_CHECK_HEADERS([X11/extensions/scrnsaver.h], [], [],
          [[#include <X11/Xlib.h>
          ]])

----------------------------------------------------------------------
Hello,
configure asks me to report this, so I'm just reporting this.  Just
ignore me if this isn't interesting.  I'd be glad to help if I can
though.

address@hidden:build-linc$ ./autogen.sh --prefix=/home/noon/.prefix-linc
checking for autoconf >= 2.12...
  testing autoconf2.50... not found.
  testing autoconf... found.
checking for automake >= 1.6...
  testing automake-1.7... not found.
  testing automake-1.6... found.
checking for libtool >= 1.4.3...
  testing libtoolize... found.
checking for glib-gettext >= 2.2.0...
  testing glib-gettextize... found.
checking for pkg-config >= 0.14.0...
  testing pkg-config... found.
checking for gtk-doc >= 1.0...
  testing gtkdocize... found.
Checking for required M4 macros...
Checking for forbidden M4 macros...
Processing ./configure.in
Running aclocal-1.6...
Running libtoolize...
Running gtkdocize...
Running autoheader...
WARNING: Using auxiliary files such as `acconfig.h', `config.h.bot'
WARNING: and `config.h.top', to define templates for `config.h.in'
WARNING: is deprecated and discouraged.

WARNING: Using the third argument of `AC_DEFINE' and
WARNING: `AC_DEFINE_UNQUOTED' allows to define a template without
WARNING: `acconfig.h':

WARNING:   AC_DEFINE([NEED_MAIN], 1,
WARNING:             [Define if a function `main' is needed.])

WARNING: More sophisticated templates can also be produced, see the
WARNING: documentation.
Running automake-1.6...
configure.in: installing `./install-sh'
configure.in: installing `./mkinstalldirs'
configure.in: installing `./missing'
Makefile.am: installing `./INSTALL'
src/Makefile.am: installing `./depcomp'
Running autoconf...
Running ./configure --enable-maintainer-mode --enable-compile-warnings 
--prefix=/home/noon/.prefix-linc ...
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking for gcc... gcc
checking for C compiler default output... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables... 
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ANSI C... none needed
checking for style of include used by make... GNU
checking dependency style of gcc... gcc3
checking for a BSD-compatible install... /usr/bin/install -c
checking build system type... i686-pc-linux-gnu
checking host system type... i686-pc-linux-gnu
checking for ld used by GCC... /usr/bin/ld
checking if the linker (/usr/bin/ld) is GNU ld... yes
checking for /usr/bin/ld option to reload object files... -r
checking for BSD-compatible nm... /usr/bin/nm -B
checking for a sed that does not truncate output... /bin/sed
checking whether ln -s works... yes
checking how to recognise dependent libraries... pass_all
checking command to parse /usr/bin/nm -B output... ok
checking how to run the C preprocessor... gcc -E
checking for egrep... grep -E
checking for ANSI C header files... yes
checking for sys/types.h... yes
checking for sys/stat.h... yes
checking for stdlib.h... yes
checking for string.h... yes
checking for memory.h... yes
checking for strings.h... yes
checking for inttypes.h... yes
checking for stdint.h... yes
checking for unistd.h... yes
checking dlfcn.h usability... yes
checking dlfcn.h presence... yes
checking for dlfcn.h... yes
checking for ranlib... ranlib
checking for strip... strip
checking for objdir... .libs
checking for gcc option to produce PIC... -fPIC
checking if gcc PIC flag -fPIC works... yes
checking if gcc static flag -static works... yes
checking if gcc supports -c -o file.o... yes
checking if gcc supports -c -o file.lo... yes
checking if gcc supports -fno-rtti -fno-exceptions... yes
checking whether the linker (/usr/bin/ld) supports shared libraries... yes
checking how to hardcode library paths into programs... immediate
checking whether stripping libraries is possible... yes
checking dynamic linker characteristics... GNU/Linux ld.so
checking if libtool supports shared libraries... yes
checking whether to build shared libraries... yes
checking whether to build static libraries... yes
checking whether -lc should be explicitly linked in... no
creating libtool
checking whether to enable maintainer-specific portions of Makefiles... yes
checking for aclocal flags... -I 
/home/noon/.prefix-gnome-common/share/aclocal/gnome2-macros -I 
/home/noon/.prefix-mozilla/share/aclocal -I 
/home/noon/.prefix-libcdaudio/share/aclocal -I 
/home/noon/.prefix-intltool/share/aclocal -I 
/home/noon/.prefix-guile-core/share/aclocal -I 
/home/noon/.prefix-gtk-doc/share/aclocal -I 
/home/noon/.prefix-gnome-common/share/aclocal -I 
/home/noon/.prefix-gettext/share/aclocal -I /usr/share/aclocal
checking for pkg-config... /usr/bin/pkg-config
checking for glib-2.0 >= 1.3.11 gobject-2.0 >= 1.3.11 gthread-2.0 >= 1.3.11... 
yes
checking LINC_CFLAGS... -pthread -I/usr/include/glib-2.0 
-I/usr/lib/glib-2.0/include  
checking LINC_LIBS... -pthread -lgobject-2.0 -lgthread-2.0 -lglib-2.0  
checking for ANSI C header files... (cached) yes
checking fcntl.h usability... yes
checking fcntl.h presence... yes
checking for fcntl.h... yes
checking for unistd.h... (cached) yes
checking sys/endian.h usability... no
checking sys/endian.h presence... no
checking for sys/endian.h... no
checking endian.h usability... yes
checking endian.h presence... yes
checking for endian.h... yes
checking machine/endian.h usability... no
checking machine/endian.h presence... no
checking for machine/endian.h... no
checking sys/machine.h usability... no
checking sys/machine.h presence... no
checking for sys/machine.h... no
checking sys/isa_defs.h usability... no
checking sys/isa_defs.h presence... no
checking for sys/isa_defs.h... no
checking sys/poll.h usability... yes
checking sys/poll.h presence... yes
checking for sys/poll.h... yes
checking stddef.h usability... yes
checking stddef.h presence... yes
checking for stddef.h... yes
checking wchar.h usability... yes
checking wchar.h presence... yes
checking for wchar.h... yes
checking wcstr.h usability... no
checking wcstr.h presence... no
checking for wcstr.h... no
checking wctype.h usability... yes
checking wctype.h presence... yes
checking for wctype.h... yes
checking machine/types.h usability... no
checking machine/types.h presence... no
checking for machine/types.h... no
checking netinet/in.h usability... yes
checking netinet/in.h presence... yes
checking for netinet/in.h... yes
checking netinet/tcp.h usability... yes
checking netinet/tcp.h presence... yes
checking for netinet/tcp.h... yes
checking sys/un.h usability... yes
checking sys/un.h presence... yes
checking for sys/un.h... yes
checking linux/irda.h usability... no
checking linux/irda.h presence... yes
configure: WARNING: linux/irda.h: present but cannot be compiled
configure: WARNING: linux/irda.h: check for missing prerequisite headers?
configure: WARNING: linux/irda.h: proceeding with the preprocessor's result
configure: WARNING:     ## ------------------------------------ ##
configure: WARNING:     ## Report this to address@hidden ##
configure: WARNING:     ## ------------------------------------ ##
checking for linux/irda.h... yes
checking arpa/nameser.h usability... yes
checking arpa/nameser.h presence... yes
checking for arpa/nameser.h... yes
checking resolv.h usability... yes
checking resolv.h presence... yes
checking for resolv.h... yes
checking for an ANSI C-conforming const... yes
checking for inline... inline
checking for size_t... yes
checking for poll... yes
checking for basename... yes
checking for res_init... no
checking for res_init in -lresolv... no
checking for socket... yes
checking for gethostbyname... yes
checking for getaddrinfo... yes
checking for getnameinfo... yes
checking for inet_pton... yes
checking for socklen_t... yes
checking if sockaddr has sa_len member... no
checking whether byte ordering is bigendian... no
checking what warning flags to pass to the C compiler... -Wall -Wunused 
-Wmissing-prototypes -Wmissing-declarations
checking gtk-doc version >= 1.0... yes
configure: creating ./config.status
config.status: creating linc.pc
config.status: creating linc.spec
config.status: creating Makefile
config.status: creating src/Makefile
config.status: creating test/Makefile
config.status: creating docs/Makefile
config.status: creating include/Makefile
config.status: creating include/linc/Makefile
config.status: creating include/linc/linc-config.h
config.status: creating linc-config
config.status: creating config.h
config.status: executing depfiles commands
config.status: executing default commands
linc configuration:

        Source code location:   .
        Compiler:               gcc

        IPv6 can do raw addrs:  yes

        This is the Development branch of linc, if
you want something more stable checkout -r gnome-2-2.

Now type `make' to compile linc
address@hidden:build-linc$ 

Have a nice day