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# include_next.m4 serial 14
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dnl Copyright (C) 2006-2010 Free Software Foundation, Inc.
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dnl This file is free software; the Free Software Foundation
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dnl gives unlimited permission to copy and/or distribute it,
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dnl with or without modifications, as long as this notice is preserved.
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dnl From Paul Eggert and Derek Price.
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dnl Sets INCLUDE_NEXT and PRAGMA_SYSTEM_HEADER.
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dnl INCLUDE_NEXT expands to 'include_next' if the compiler supports it, or to
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dnl 'include' otherwise.
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dnl INCLUDE_NEXT_AS_FIRST_DIRECTIVE expands to 'include_next' if the compiler
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dnl supports it in the special case that it is the first include directive in
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dnl the given file, or to 'include' otherwise.
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dnl PRAGMA_SYSTEM_HEADER can be used in files that contain #include_next,
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dnl so as to avoid GCC warnings when the gcc option -pedantic is used.
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dnl '#pragma GCC system_header' has the same effect as if the file was found
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dnl through the include search path specified with '-isystem' options (as
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dnl opposed to the search path specified with '-I' options). Namely, gcc
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dnl does not warn about some things, and on some systems (Solaris and Interix)
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dnl __STDC__ evaluates to 0 instead of to 1. The latter is an undesired side
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dnl effect; we are therefore careful to use 'defined __STDC__' or '1' instead
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dnl of plain '__STDC__'.
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AC_DEFUN([gl_INCLUDE_NEXT],
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AC_LANG_PREPROC_REQUIRE()
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AC_CACHE_CHECK([whether the preprocessor supports include_next],
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[gl_cv_have_include_next],
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[rm -rf conftestd1a conftestd1b conftestd2
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mkdir conftestd1a conftestd1b conftestd2
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dnl IBM C 9.0, 10.1 (original versions, prior to the 2009-01 updates) on
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dnl AIX 6.1 support include_next when used as first preprocessor directive
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dnl in a file, but not when preceded by another include directive. Check
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dnl for this bug by including <stdio.h>.
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dnl Additionally, with this same compiler, include_next is a no-op when
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dnl used in a header file that was included by specifying its absolute
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dnl file name. Despite these two bugs, include_next is used in the
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dnl compiler's <math.h>. By virtue of the second bug, we need to use
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dnl include_next as well in this case.
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cat <<EOF > conftestd1a/conftest.h
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#define DEFINED_IN_CONFTESTD1
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#include_next <conftest.h>
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#ifdef DEFINED_IN_CONFTESTD2
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#error "include_next doesn't work"
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cat <<EOF > conftestd1b/conftest.h
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#define DEFINED_IN_CONFTESTD1
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#include_next <conftest.h>
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#ifdef DEFINED_IN_CONFTESTD2
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#error "include_next doesn't work"
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cat <<EOF > conftestd2/conftest.h
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#ifndef DEFINED_IN_CONFTESTD1
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#error "include_next test doesn't work"
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#define DEFINED_IN_CONFTESTD2
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gl_save_CPPFLAGS="$CPPFLAGS"
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CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2"
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AC_COMPILE_IFELSE([#include <conftest.h>],
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[gl_cv_have_include_next=yes],
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[CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2"
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AC_COMPILE_IFELSE([#include <conftest.h>],
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[gl_cv_have_include_next=buggy],
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[gl_cv_have_include_next=no])
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CPPFLAGS="$gl_save_CPPFLAGS"
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rm -rf conftestd1a conftestd1b conftestd2
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if test $gl_cv_have_include_next = yes; then
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INCLUDE_NEXT=include_next
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INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
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if test -n "$GCC"; then
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PRAGMA_SYSTEM_HEADER='#pragma GCC system_header'
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if test $gl_cv_have_include_next = buggy; then
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INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
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INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include
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AC_SUBST([INCLUDE_NEXT])
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AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE])
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AC_SUBST([PRAGMA_SYSTEM_HEADER])
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# gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...)
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# ------------------------------------------
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# For each arg foo.h, if #include_next works, define NEXT_FOO_H to be
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# '<foo.h>'; otherwise define it to be
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# '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
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# Also, if #include_next works as first preprocessing directive in a file,
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# define NEXT_AS_FIRST_DIRECTIVE_FOO_H to be '<foo.h>'; otherwise define it to
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# '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
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# That way, a header file with the following line:
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# #@INCLUDE_NEXT@ @NEXT_FOO_H@
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# #@INCLUDE_NEXT_AS_FIRST_DIRECTIVE@ @NEXT_AS_FIRST_DIRECTIVE_FOO_H@
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# behaves (after sed substitution) as if it contained
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# #include_next <foo.h>
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# even if the compiler does not support include_next.
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# The three "///" are to pacify Sun C 5.8, which otherwise would say
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# "warning: #include of /usr/include/... may be non-portable".
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# Use `""', not `<>', so that the /// cannot be confused with a C99 comment.
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# Note: This macro assumes that the header file is not empty after
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# preprocessing, i.e. it does not only define preprocessor macros but also
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# provides some type/enum definitions or function/variable declarations.
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AC_DEFUN([gl_CHECK_NEXT_HEADERS],
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AC_REQUIRE([gl_INCLUDE_NEXT])
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AC_REQUIRE([AC_CANONICAL_HOST])
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AC_CHECK_HEADERS_ONCE([$1])
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m4_foreach_w([gl_HEADER_NAME], [$1],
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[AS_VAR_PUSHDEF([gl_next_header],
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[gl_cv_next_]m4_defn([gl_HEADER_NAME]))
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if test $gl_cv_have_include_next = yes; then
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AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
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[absolute name of <]m4_defn([gl_HEADER_NAME])[>],
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m4_defn([gl_next_header]),
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[AS_VAR_PUSHDEF([gl_header_exists],
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[ac_cv_header_]m4_defn([gl_HEADER_NAME]))
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if test AS_VAR_GET(gl_header_exists) = yes; then
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[[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]]
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dnl AIX "xlc -E" and "cc -E" omit #line directives for header files
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dnl that contain only a #include of other header files and no
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dnl non-comment tokens of their own. This leads to a failure to
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dnl detect the absolute name of <dirent.h>, <signal.h>, <poll.h>
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dnl and others. The workaround is to force preservation of comments
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dnl through option -C. This ensures all necessary #line directives
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dnl are present. GCC supports option -C as well.
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aix*) gl_absname_cpp="$ac_cpp -C" ;;
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*) gl_absname_cpp="$ac_cpp" ;;
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dnl eval is necessary to expand gl_absname_cpp.
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dnl Ultrix and Pyramid sh refuse to redirect output of eval,
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AS_VAR_SET([gl_next_header],
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['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |
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sed -n '\#/]m4_defn([gl_HEADER_NAME])[#{
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s#.*"\(.*/]m4_defn([gl_HEADER_NAME])[\)".*#\1#
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AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
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AS_VAR_POPDEF([gl_header_exists])])
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AS_TR_CPP([NEXT_]m4_defn([gl_HEADER_NAME])),
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[AS_VAR_GET([gl_next_header])])
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if test $gl_cv_have_include_next = yes || test $gl_cv_have_include_next = buggy; then
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# INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include_next'
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gl_next_as_first_directive='<'gl_HEADER_NAME'>'
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# INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include'
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gl_next_as_first_directive=AS_VAR_GET([gl_next_header])
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AS_TR_CPP([NEXT_AS_FIRST_DIRECTIVE_]m4_defn([gl_HEADER_NAME])),
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[$gl_next_as_first_directive])
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AS_VAR_POPDEF([gl_next_header])])
added
removed
m4/include_next.m4
