# absolute-header.m4 serial 16

dnl Copyright (C) 2006-2020 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 Derek Price.

# gl_ABSOLUTE_HEADER(HEADER1 HEADER2 ...)

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

# Find the absolute name of a header file, testing first if the header exists.

# If the header were sys/inttypes.h, this macro would define

# ABSOLUTE_SYS_INTTYPES_H to the '""' quoted absolute name of sys/inttypes.h

# in config.h

# (e.g. '#define ABSOLUTE_SYS_INTTYPES_H "///usr/include/sys/inttypes.h"').

# 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_ABSOLUTE_HEADER],

[AC_REQUIRE([AC_CANONICAL_HOST])

AC_LANG_PREPROC_REQUIRE()dnl

dnl FIXME: gl_absolute_header and ac_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_absolute_header],

                  [gl_cv_absolute_]m4_defn([gl_HEADER_NAME]))dnl

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

    m4_defn([gl_absolute_header]),

    [AS_VAR_PUSHDEF([ac_header_exists],

                    [ac_cv_header_]m4_defn([gl_HEADER_NAME]))dnl

    AC_CHECK_HEADERS_ONCE(m4_defn([gl_HEADER_NAME]))dnl

    if test AS_VAR_GET(ac_header_exists) = yes; then

      gl_ABSOLUTE_HEADER_ONE(m4_defn([gl_HEADER_NAME]))

    fi

    AS_VAR_POPDEF([ac_header_exists])dnl

    ])dnl

  AC_DEFINE_UNQUOTED(AS_TR_CPP([ABSOLUTE_]m4_defn([gl_HEADER_NAME])),

                     ["AS_VAR_GET(gl_absolute_header)"],

                     [Define this to an absolute name of <]m4_defn([gl_HEADER_NAME])[>.])

  AS_VAR_POPDEF([gl_absolute_header])dnl

])dnl

])# gl_ABSOLUTE_HEADER

# gl_ABSOLUTE_HEADER_ONE(HEADER)

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

# Like gl_ABSOLUTE_HEADER, except that:

#   - it assumes that the header exists,

#   - it uses the current CPPFLAGS,

#   - it does not cache the result,

#   - it is silent.

AC_DEFUN([gl_ABSOLUTE_HEADER_ONE],

[

  AC_REQUIRE([AC_CANONICAL_HOST])

  AC_LANG_CONFTEST([AC_LANG_SOURCE([[#include <]]m4_dquote([$1])[[>]])])

  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

changequote(,)

  case "$host_os" in

    mingw*)

      dnl For the sake of native Windows compilers (excluding gcc),

      dnl treat backslash as a directory separator, like /.

      dnl Actually, these compilers use a double-backslash as

      dnl directory separator, inside the

      dnl   # line "filename"

      dnl directives.

      gl_dirsep_regex='[/\\]'

      ;;

    *)

      gl_dirsep_regex='\/'

      ;;

  esac

  dnl A sed expression that turns a string into a basic regular

  dnl expression, for use within "/.../".

  gl_make_literal_regex_sed='s,[]$^\\.*/[],\\&,g'

  gl_header_literal_regex=`echo '$1' \

                           | sed -e "$gl_make_literal_regex_sed"`

  gl_absolute_header_sed="/${gl_dirsep_regex}${gl_header_literal_regex}/"'{

      s/.*"\(.*'"${gl_dirsep_regex}${gl_header_literal_regex}"'\)".*/\1/

      s|^/[^/]|//&|

      p

      q

    }'

changequote([,])

  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_cv_absolute_]AS_TR_SH([[$1]]),

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

  sed -n "$gl_absolute_header_sed"`])

])