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# include_next.m4 serial 14

dnl Copyright (C) 2006-2010 Free Software Foundation, Inc.

dnl This file is free software; the Free Software Foundation

dnl gives unlimited permission to copy and/or distribute it,

dnl with or without modifications, as long as this notice is preserved.

dnl From Paul Eggert and Derek Price.

dnl Sets INCLUDE_NEXT and PRAGMA_SYSTEM_HEADER.

dnl

dnl INCLUDE_NEXT expands to 'include_next' if the compiler supports it, or to

dnl 'include' otherwise.

dnl

dnl INCLUDE_NEXT_AS_FIRST_DIRECTIVE expands to 'include_next' if the compiler

dnl supports it in the special case that it is the first include directive in

dnl the given file, or to 'include' otherwise.

dnl

dnl PRAGMA_SYSTEM_HEADER can be used in files that contain #include_next,

dnl so as to avoid GCC warnings when the gcc option -pedantic is used.

dnl '#pragma GCC system_header' has the same effect as if the file was found

dnl through the include search path specified with '-isystem' options (as

dnl opposed to the search path specified with '-I' options). Namely, gcc

dnl does not warn about some things, and on some systems (Solaris and Interix)

dnl __STDC__ evaluates to 0 instead of to 1. The latter is an undesired side

dnl effect; we are therefore careful to use 'defined __STDC__' or '1' instead

dnl of plain '__STDC__'.

AC_DEFUN([gl_INCLUDE_NEXT],

[

  AC_LANG_PREPROC_REQUIRE()

  AC_CACHE_CHECK([whether the preprocessor supports include_next],

    [gl_cv_have_include_next],

    [rm -rf conftestd1a conftestd1b conftestd2

     mkdir conftestd1a conftestd1b conftestd2

     dnl IBM C 9.0, 10.1 (original versions, prior to the 2009-01 updates) on

     dnl AIX 6.1 support include_next when used as first preprocessor directive

     dnl in a file, but not when preceded by another include directive. Check

     dnl for this bug by including <stdio.h>.

     dnl Additionally, with this same compiler, include_next is a no-op when

     dnl used in a header file that was included by specifying its absolute

     dnl file name. Despite these two bugs, include_next is used in the

     dnl compiler's <math.h>. By virtue of the second bug, we need to use

     dnl include_next as well in this case.

     cat <<EOF > conftestd1a/conftest.h

#define DEFINED_IN_CONFTESTD1

#include_next <conftest.h>

#ifdef DEFINED_IN_CONFTESTD2

int foo;

#else

#error "include_next doesn't work"

#endif

EOF

     cat <<EOF > conftestd1b/conftest.h

#define DEFINED_IN_CONFTESTD1

#include <stdio.h>

#include_next <conftest.h>

#ifdef DEFINED_IN_CONFTESTD2

int foo;

#else

#error "include_next doesn't work"

#endif

EOF

     cat <<EOF > conftestd2/conftest.h

#ifndef DEFINED_IN_CONFTESTD1

#error "include_next test doesn't work"

#endif

#define DEFINED_IN_CONFTESTD2

EOF

     gl_save_CPPFLAGS="$CPPFLAGS"

     CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2"

     AC_COMPILE_IFELSE([#include <conftest.h>],

       [gl_cv_have_include_next=yes],

       [CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2"

        AC_COMPILE_IFELSE([#include <conftest.h>],

          [gl_cv_have_include_next=buggy],

          [gl_cv_have_include_next=no])

       ])

     CPPFLAGS="$gl_save_CPPFLAGS"

     rm -rf conftestd1a conftestd1b conftestd2

    ])

  PRAGMA_SYSTEM_HEADER=

  if test $gl_cv_have_include_next = yes; then

    INCLUDE_NEXT=include_next

    INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next

    if test -n "$GCC"; then

      PRAGMA_SYSTEM_HEADER='#pragma GCC system_header'

    fi

  else

    if test $gl_cv_have_include_next = buggy; then

      INCLUDE_NEXT=include

      INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next

    else

      INCLUDE_NEXT=include

      INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include

    fi

  fi

  AC_SUBST([INCLUDE_NEXT])

  AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE])

  AC_SUBST([PRAGMA_SYSTEM_HEADER])

])

# gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...)

# ------------------------------------------

# For each arg foo.h, if #include_next works, define NEXT_FOO_H to be

# '<foo.h>'; otherwise define it to be

# '"///usr/include/foo.h"', or whatever other absolute file name is suitable.

# Also, if #include_next works as first preprocessing directive in a file,

# define NEXT_AS_FIRST_DIRECTIVE_FOO_H to be '<foo.h>'; otherwise define it to

# be

# '"///usr/include/foo.h"', or whatever other absolute file name is suitable.

# That way, a header file with the following line:

#       #@INCLUDE_NEXT@ @NEXT_FOO_H@

# or

#       #@INCLUDE_NEXT_AS_FIRST_DIRECTIVE@ @NEXT_AS_FIRST_DIRECTIVE_FOO_H@

# behaves (after sed substitution) as if it contained

#       #include_next <foo.h>

# even if the compiler does not support include_next.

# The three "///" are to pacify Sun C 5.8, which otherwise would say

# "warning: #include of /usr/include/... may be non-portable".

# Use `""', not `<>', so that the /// cannot be confused with a C99 comment.

# Note: This macro assumes that the header file is not empty after

# preprocessing, i.e. it does not only define preprocessor macros but also

# provides some type/enum definitions or function/variable declarations.

AC_DEFUN([gl_CHECK_NEXT_HEADERS],

[

  AC_REQUIRE([gl_INCLUDE_NEXT])

  AC_REQUIRE([AC_CANONICAL_HOST])

  AC_CHECK_HEADERS_ONCE([$1])

  m4_foreach_w([gl_HEADER_NAME], [$1],

    [AS_VAR_PUSHDEF([gl_next_header],

                    [gl_cv_next_]m4_defn([gl_HEADER_NAME]))

     if test $gl_cv_have_include_next = yes; then

       AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])

     else

       AC_CACHE_CHECK(

         [absolute name of <]m4_defn([gl_HEADER_NAME])[>],

         m4_defn([gl_next_header]),

         [AS_VAR_PUSHDEF([gl_header_exists],

                         [ac_cv_header_]m4_defn([gl_HEADER_NAME]))

          if test AS_VAR_GET(gl_header_exists) = yes; then

            AC_LANG_CONFTEST(

              [AC_LANG_SOURCE(

                 [[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]]

               )])

            dnl AIX "xlc -E" and "cc -E" omit #line directives for header files

            dnl that contain only a #include of other header files and no

            dnl non-comment tokens of their own. This leads to a failure to

            dnl detect the absolute name of <dirent.h>, <signal.h>, <poll.h>

            dnl and others. The workaround is to force preservation of comments

            dnl through option -C. This ensures all necessary #line directives

            dnl are present. GCC supports option -C as well.

            case "$host_os" in

              aix*) gl_absname_cpp="$ac_cpp -C" ;;

              *)    gl_absname_cpp="$ac_cpp" ;;

            esac

            dnl eval is necessary to expand gl_absname_cpp.

            dnl Ultrix and Pyramid sh refuse to redirect output of eval,

            dnl so use subshell.

            AS_VAR_SET([gl_next_header],

              ['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |

               sed -n '\#/]m4_defn([gl_HEADER_NAME])[#{

                 s#.*"\(.*/]m4_defn([gl_HEADER_NAME])[\)".*#\1#

                 s#^/[^/]#//&#

                 p

                 q

               }'`'"'])

          else

            AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])

          fi

          AS_VAR_POPDEF([gl_header_exists])])

     fi

     AC_SUBST(

       AS_TR_CPP([NEXT_]m4_defn([gl_HEADER_NAME])),

       [AS_VAR_GET([gl_next_header])])

     if test $gl_cv_have_include_next = yes || test $gl_cv_have_include_next = buggy; then

       # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include_next'

       gl_next_as_first_directive='<'gl_HEADER_NAME'>'

     else

       # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include'

       gl_next_as_first_directive=AS_VAR_GET([gl_next_header])

     fi

     AC_SUBST(

       AS_TR_CPP([NEXT_AS_FIRST_DIRECTIVE_]m4_defn([gl_HEADER_NAME])),

       [$gl_next_as_first_directive])

     AS_VAR_POPDEF([gl_next_header])])

])