gnulib/import/m4/include_next.m4

   1 # include_next.m4 serial 24
   2 dnl Copyright (C) 2006-2019 Free Software Foundation, Inc.
   3 dnl This file is free software; the Free Software Foundation
   4 dnl gives unlimited permission to copy and/or distribute it,
   5 dnl with or without modifications, as long as this notice is preserved.
   6
   7 dnl From Paul Eggert and Derek Price.
   8
   9 dnl Sets INCLUDE_NEXT, INCLUDE_NEXT_AS_FIRST_DIRECTIVE, PRAGMA_SYSTEM_HEADER,
  10 dnl and PRAGMA_COLUMNS.
  11 dnl
  12 dnl INCLUDE_NEXT expands to 'include_next' if the compiler supports it, or to
  13 dnl 'include' otherwise.
  14 dnl
  15 dnl INCLUDE_NEXT_AS_FIRST_DIRECTIVE expands to 'include_next' if the compiler
  16 dnl supports it in the special case that it is the first include directive in
  17 dnl the given file, or to 'include' otherwise.
  18 dnl
  19 dnl PRAGMA_SYSTEM_HEADER can be used in files that contain #include_next,
  20 dnl so as to avoid GCC warnings when the gcc option -pedantic is used.
  21 dnl '#pragma GCC system_header' has the same effect as if the file was found
  22 dnl through the include search path specified with '-isystem' options (as
  23 dnl opposed to the search path specified with '-I' options). Namely, gcc
  24 dnl does not warn about some things, and on some systems (Solaris and Interix)
  25 dnl __STDC__ evaluates to 0 instead of to 1. The latter is an undesired side
  26 dnl effect; we are therefore careful to use 'defined __STDC__' or '1' instead
  27 dnl of plain '__STDC__'.
  28 dnl
  29 dnl PRAGMA_COLUMNS can be used in files that override system header files, so
  30 dnl as to avoid compilation errors on HP NonStop systems when the gnulib file
  31 dnl is included by a system header file that does a "#pragma COLUMNS 80" (which
  32 dnl has the effect of truncating the lines of that file and all files that it
  33 dnl includes to 80 columns) and the gnulib file has lines longer than 80
  34 dnl columns.
  35
  36 AC_DEFUN([gl_INCLUDE_NEXT],
  37 [
  38   AC_LANG_PREPROC_REQUIRE()
  39   AC_CACHE_CHECK([whether the preprocessor supports include_next],
  40     [gl_cv_have_include_next],
  41     [rm -rf conftestd1a conftestd1b conftestd2
  42      mkdir conftestd1a conftestd1b conftestd2
  43      dnl IBM C 9.0, 10.1 (original versions, prior to the 2009-01 updates) on
  44      dnl AIX 6.1 support include_next when used as first preprocessor directive
  45      dnl in a file, but not when preceded by another include directive. Check
  46      dnl for this bug by including <stdio.h>.
  47      dnl Additionally, with this same compiler, include_next is a no-op when
  48      dnl used in a header file that was included by specifying its absolute
  49      dnl file name. Despite these two bugs, include_next is used in the
  50      dnl compiler's <math.h>. By virtue of the second bug, we need to use
  51      dnl include_next as well in this case.
  52      cat <<EOF > conftestd1a/conftest.h
  53 #define DEFINED_IN_CONFTESTD1
  54 #include_next <conftest.h>
  55 #ifdef DEFINED_IN_CONFTESTD2
  56 int foo;
  57 #else
  58 #error "include_next doesn't work"
  59 #endif
  60 EOF
  61      cat <<EOF > conftestd1b/conftest.h
  62 #define DEFINED_IN_CONFTESTD1
  63 #include <stdio.h>
  64 #include_next <conftest.h>
  65 #ifdef DEFINED_IN_CONFTESTD2
  66 int foo;
  67 #else
  68 #error "include_next doesn't work"
  69 #endif
  70 EOF
  71      cat <<EOF > conftestd2/conftest.h
  72 #ifndef DEFINED_IN_CONFTESTD1
  73 #error "include_next test doesn't work"
  74 #endif
  75 #define DEFINED_IN_CONFTESTD2
  76 EOF
  77      gl_save_CPPFLAGS="$CPPFLAGS"
  78      CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2"
  79 dnl We intentionally avoid using AC_LANG_SOURCE here.
  80      AC_COMPILE_IFELSE([AC_LANG_DEFINES_PROVIDED[#include <conftest.h>]],
  81        [gl_cv_have_include_next=yes],
  82        [CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2"
  83         AC_COMPILE_IFELSE([AC_LANG_DEFINES_PROVIDED[#include <conftest.h>]],
  84           [gl_cv_have_include_next=buggy],
  85           [gl_cv_have_include_next=no])
  86        ])
  87      CPPFLAGS="$gl_save_CPPFLAGS"
  88      rm -rf conftestd1a conftestd1b conftestd2
  89     ])
  90   PRAGMA_SYSTEM_HEADER=
  91   if test $gl_cv_have_include_next = yes; then
  92     INCLUDE_NEXT=include_next
  93     INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
  94     if test -n "$GCC"; then
  95       PRAGMA_SYSTEM_HEADER='#pragma GCC system_header'
  96     fi
  97   else
  98     if test $gl_cv_have_include_next = buggy; then
  99       INCLUDE_NEXT=include
 100       INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
 101     else
 102       INCLUDE_NEXT=include
 103       INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include
 104     fi
 105   fi
 106   AC_SUBST([INCLUDE_NEXT])
 107   AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE])
 108   AC_SUBST([PRAGMA_SYSTEM_HEADER])
 109   AC_CACHE_CHECK([whether system header files limit the line length],
 110     [gl_cv_pragma_columns],
 111     [dnl HP NonStop systems, which define __TANDEM, have this misfeature.
 112      AC_EGREP_CPP([choke me],
 113        [
 114 #ifdef __TANDEM
 115 choke me
 116 #endif
 117        ],
 118        [gl_cv_pragma_columns=yes],
 119        [gl_cv_pragma_columns=no])
 120     ])
 121   if test $gl_cv_pragma_columns = yes; then
 122     PRAGMA_COLUMNS="#pragma COLUMNS 10000"
 123   else
 124     PRAGMA_COLUMNS=
 125   fi
 126   AC_SUBST([PRAGMA_COLUMNS])
 127 ])
 128
 129 # gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...)
 130 # ------------------------------------------
 131 # For each arg foo.h, if #include_next works, define NEXT_FOO_H to be
 132 # '<foo.h>'; otherwise define it to be
 133 # '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
 134 # Also, if #include_next works as first preprocessing directive in a file,
 135 # define NEXT_AS_FIRST_DIRECTIVE_FOO_H to be '<foo.h>'; otherwise define it to
 136 # be
 137 # '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
 138 # That way, a header file with the following line:
 139 #       #@INCLUDE_NEXT@ @NEXT_FOO_H@
 140 # or
 141 #       #@INCLUDE_NEXT_AS_FIRST_DIRECTIVE@ @NEXT_AS_FIRST_DIRECTIVE_FOO_H@
 142 # behaves (after sed substitution) as if it contained
 143 #       #include_next <foo.h>
 144 # even if the compiler does not support include_next.
 145 # The three "///" are to pacify Sun C 5.8, which otherwise would say
 146 # "warning: #include of /usr/include/... may be non-portable".
 147 # Use '""', not '<>', so that the /// cannot be confused with a C99 comment.
 148 # Note: This macro assumes that the header file is not empty after
 149 # preprocessing, i.e. it does not only define preprocessor macros but also
 150 # provides some type/enum definitions or function/variable declarations.
 151 #
 152 # This macro also checks whether each header exists, by invoking
 153 # AC_CHECK_HEADERS_ONCE or AC_CHECK_HEADERS on each argument.
 154 AC_DEFUN([gl_CHECK_NEXT_HEADERS],
 155 [
 156   gl_NEXT_HEADERS_INTERNAL([$1], [check])
 157 ])
 158
 159 # gl_NEXT_HEADERS(HEADER1 HEADER2 ...)
 160 # ------------------------------------
 161 # Like gl_CHECK_NEXT_HEADERS, except do not check whether the headers exist.
 162 # This is suitable for headers like <stddef.h> that are standardized by C89
 163 # and therefore can be assumed to exist.
 164 AC_DEFUN([gl_NEXT_HEADERS],
 165 [
 166   gl_NEXT_HEADERS_INTERNAL([$1], [assume])
 167 ])
 168
 169 # The guts of gl_CHECK_NEXT_HEADERS and gl_NEXT_HEADERS.
 170 AC_DEFUN([gl_NEXT_HEADERS_INTERNAL],
 171 [
 172   AC_REQUIRE([gl_INCLUDE_NEXT])
 173   AC_REQUIRE([AC_CANONICAL_HOST])
 174
 175   m4_if([$2], [check],
 176     [AC_CHECK_HEADERS_ONCE([$1])
 177     ])
 178
 179 dnl FIXME: gl_next_header and gl_header_exists must be used unquoted
 180 dnl until we can assume autoconf 2.64 or newer.
 181   m4_foreach_w([gl_HEADER_NAME], [$1],
 182     [AS_VAR_PUSHDEF([gl_next_header],
 183                     [gl_cv_next_]m4_defn([gl_HEADER_NAME]))
 184      if test $gl_cv_have_include_next = yes; then
 185        AS_VAR_SET(gl_next_header, ['<'gl_HEADER_NAME'>'])
 186      else
 187        AC_CACHE_CHECK(
 188          [absolute name of <]m4_defn([gl_HEADER_NAME])[>],
 189          m4_defn([gl_next_header]),
 190          [m4_if([$2], [check],
 191             [AS_VAR_PUSHDEF([gl_header_exists],
 192                             [ac_cv_header_]m4_defn([gl_HEADER_NAME]))
 193              if test AS_VAR_GET(gl_header_exists) = yes; then
 194              AS_VAR_POPDEF([gl_header_exists])
 195             ])
 196            gl_ABSOLUTE_HEADER_ONE(gl_HEADER_NAME)
 197            AS_VAR_COPY([gl_header], [gl_cv_absolute_]AS_TR_SH(gl_HEADER_NAME))
 198            AS_VAR_SET(gl_next_header, ['"'$gl_header'"'])
 199           m4_if([$2], [check],
 200             [else
 201                AS_VAR_SET(gl_next_header, ['<'gl_HEADER_NAME'>'])
 202              fi
 203             ])
 204          ])
 205      fi
 206      AC_SUBST(
 207        AS_TR_CPP([NEXT_]m4_defn([gl_HEADER_NAME])),
 208        [AS_VAR_GET(gl_next_header)])
 209      if test $gl_cv_have_include_next = yes || test $gl_cv_have_include_next = buggy; then
 210        # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include_next'
 211        gl_next_as_first_directive='<'gl_HEADER_NAME'>'
 212      else
 213        # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include'
 214        gl_next_as_first_directive=AS_VAR_GET(gl_next_header)
 215      fi
 216      AC_SUBST(
 217        AS_TR_CPP([NEXT_AS_FIRST_DIRECTIVE_]m4_defn([gl_HEADER_NAME])),
 218        [$gl_next_as_first_directive])
 219      AS_VAR_POPDEF([gl_next_header])])
 220 ])
 221
 222 # Autoconf 2.68 added warnings for our use of AC_COMPILE_IFELSE;
 223 # this fallback is safe for all earlier autoconf versions.
 224 m4_define_default([AC_LANG_DEFINES_PROVIDED])