include_next: minimize code duplication

[gnulib.git] / m4 / include_next.m4

diff --git a/m4/include_next.m4 b/m4/include_next.m4
index b3c7849..f09dbe6 100644 (file)
--- a/m4/include_next.m4
+++ b/m4/include_next.m4
@@ -1,5 +1,5 @@
-# include_next.m4 serial 18
-dnl Copyright (C) 2006-2011 Free Software Foundation, Inc.
+# include_next.m4 serial 23
+dnl Copyright (C) 2006-2013 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.
@@ -143,7 +143,7 @@ choke me
 # 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.
+# 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.
@@ -175,11 +175,13 @@ AC_DEFUN([gl_NEXT_HEADERS_INTERNAL],
     [AC_CHECK_HEADERS_ONCE([$1])
     ])
 
+dnl FIXME: gl_next_header and gl_header_exists must be used unquoted
+dnl until we can assume autoconf 2.64 or newer.
   m4_foreach_w([gl_HEADER_NAME], [$1],
     [AS_VAR_PUSHDEF([gl_next_header],
                     [gl_cv_next_]m4_defn([gl_HEADER_NAME]))
      if test $gl_cv_have_include_next = yes; then
-       AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
+       AS_VAR_SET(gl_next_header, ['<'gl_HEADER_NAME'>'])
      else
        AC_CACHE_CHECK(
          [absolute name of <]m4_defn([gl_HEADER_NAME])[>],
@@ -190,48 +192,25 @@ AC_DEFUN([gl_NEXT_HEADERS_INTERNAL],
              if test AS_VAR_GET(gl_header_exists) = yes; then
              AS_VAR_POPDEF([gl_header_exists])
             ])
-               AC_LANG_CONFTEST(
-                 [AC_LANG_SOURCE(
-                    [[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]]
-                  )])
-               dnl AIX "xlc -E" and "cc -E" omit #line directives for header
-               dnl files that contain only a #include of other header files and
-               dnl no non-comment tokens of their own. This leads to a failure
-               dnl to detect the absolute name of <dirent.h>, <signal.h>,
-               dnl <poll.h> and others. The workaround is to force preservation
-               dnl of comments through option -C. This ensures all necessary
-               dnl #line directives are present. GCC supports option -C as well.
-               case "$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
-                  }'`'"'])
+           gl_ABSOLUTE_HEADER_ONE(gl_HEADER_NAME)
+           AS_VAR_COPY([gl_header], [gl_cv_absolute_]AS_TR_SH(gl_HEADER_NAME))
+           AS_VAR_SET(gl_next_header, ['"'$gl_header'"'])
           m4_if([$2], [check],
             [else
-               AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
+               AS_VAR_SET(gl_next_header, ['<'gl_HEADER_NAME'>'])
              fi
             ])
          ])
      fi
      AC_SUBST(
        AS_TR_CPP([NEXT_]m4_defn([gl_HEADER_NAME])),
-       [AS_VAR_GET([gl_next_header])])
+       [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])
+       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])),