1# include_next.m4 serial 23
2dnl Copyright (C) 2006-2012 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7dnl From Paul Eggert and Derek Price.
8
9dnl Sets INCLUDE_NEXT and PRAGMA_SYSTEM_HEADER.
10dnl
11dnl INCLUDE_NEXT expands to 'include_next' if the compiler supports it, or to
12dnl 'include' otherwise.
13dnl
14dnl INCLUDE_NEXT_AS_FIRST_DIRECTIVE expands to 'include_next' if the compiler
15dnl supports it in the special case that it is the first include directive in
16dnl the given file, or to 'include' otherwise.
17dnl
18dnl PRAGMA_SYSTEM_HEADER can be used in files that contain #include_next,
19dnl so as to avoid GCC warnings when the gcc option -pedantic is used.
20dnl '#pragma GCC system_header' has the same effect as if the file was found
21dnl through the include search path specified with '-isystem' options (as
22dnl opposed to the search path specified with '-I' options). Namely, gcc
23dnl does not warn about some things, and on some systems (Solaris and Interix)
24dnl __STDC__ evaluates to 0 instead of to 1. The latter is an undesired side
25dnl effect; we are therefore careful to use 'defined __STDC__' or '1' instead
26dnl of plain '__STDC__'.
27dnl
28dnl PRAGMA_COLUMNS can be used in files that override system header files, so
29dnl as to avoid compilation errors on HP NonStop systems when the gnulib file
30dnl is included by a system header file that does a "#pragma COLUMNS 80" (which
31dnl has the effect of truncating the lines of that file and all files that it
32dnl includes to 80 columns) and the gnulib file has lines longer than 80
33dnl columns.
34
35AC_DEFUN([gl_INCLUDE_NEXT],
36[
37  AC_LANG_PREPROC_REQUIRE()
38  AC_CACHE_CHECK([whether the preprocessor supports include_next],
39    [gl_cv_have_include_next],
40    [rm -rf conftestd1a conftestd1b conftestd2
41     mkdir conftestd1a conftestd1b conftestd2
42     dnl IBM C 9.0, 10.1 (original versions, prior to the 2009-01 updates) on
43     dnl AIX 6.1 support include_next when used as first preprocessor directive
44     dnl in a file, but not when preceded by another include directive. Check
45     dnl for this bug by including <stdio.h>.
46     dnl Additionally, with this same compiler, include_next is a no-op when
47     dnl used in a header file that was included by specifying its absolute
48     dnl file name. Despite these two bugs, include_next is used in the
49     dnl compiler's <math.h>. By virtue of the second bug, we need to use
50     dnl include_next as well in this case.
51     cat <<EOF > conftestd1a/conftest.h
52#define DEFINED_IN_CONFTESTD1
53#include_next <conftest.h>
54#ifdef DEFINED_IN_CONFTESTD2
55int foo;
56#else
57#error "include_next doesn't work"
58#endif
59EOF
60     cat <<EOF > conftestd1b/conftest.h
61#define DEFINED_IN_CONFTESTD1
62#include <stdio.h>
63#include_next <conftest.h>
64#ifdef DEFINED_IN_CONFTESTD2
65int foo;
66#else
67#error "include_next doesn't work"
68#endif
69EOF
70     cat <<EOF > conftestd2/conftest.h
71#ifndef DEFINED_IN_CONFTESTD1
72#error "include_next test doesn't work"
73#endif
74#define DEFINED_IN_CONFTESTD2
75EOF
76     gl_save_CPPFLAGS="$CPPFLAGS"
77     CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2"
78dnl We intentionally avoid using AC_LANG_SOURCE here.
79     AC_COMPILE_IFELSE([AC_LANG_DEFINES_PROVIDED[#include <conftest.h>]],
80       [gl_cv_have_include_next=yes],
81       [CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2"
82        AC_COMPILE_IFELSE([AC_LANG_DEFINES_PROVIDED[#include <conftest.h>]],
83          [gl_cv_have_include_next=buggy],
84          [gl_cv_have_include_next=no])
85       ])
86     CPPFLAGS="$gl_save_CPPFLAGS"
87     rm -rf conftestd1a conftestd1b conftestd2
88    ])
89  PRAGMA_SYSTEM_HEADER=
90  if test $gl_cv_have_include_next = yes; then
91    INCLUDE_NEXT=include_next
92    INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
93    if test -n "$GCC"; then
94      PRAGMA_SYSTEM_HEADER='#pragma GCC system_header'
95    fi
96  else
97    if test $gl_cv_have_include_next = buggy; then
98      INCLUDE_NEXT=include
99      INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
100    else
101      INCLUDE_NEXT=include
102      INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include
103    fi
104  fi
105  AC_SUBST([INCLUDE_NEXT])
106  AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE])
107  AC_SUBST([PRAGMA_SYSTEM_HEADER])
108  AC_CACHE_CHECK([whether system header files limit the line length],
109    [gl_cv_pragma_columns],
110    [dnl HP NonStop systems, which define __TANDEM, have this misfeature.
111     AC_EGREP_CPP([choke me],
112       [
113#ifdef __TANDEM
114choke me
115#endif
116       ],
117       [gl_cv_pragma_columns=yes],
118       [gl_cv_pragma_columns=no])
119    ])
120  if test $gl_cv_pragma_columns = yes; then
121    PRAGMA_COLUMNS="#pragma COLUMNS 10000"
122  else
123    PRAGMA_COLUMNS=
124  fi
125  AC_SUBST([PRAGMA_COLUMNS])
126])
127
128# gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...)
129# ------------------------------------------
130# For each arg foo.h, if #include_next works, define NEXT_FOO_H to be
131# '<foo.h>'; otherwise define it to be
132# '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
133# Also, if #include_next works as first preprocessing directive in a file,
134# define NEXT_AS_FIRST_DIRECTIVE_FOO_H to be '<foo.h>'; otherwise define it to
135# be
136# '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
137# That way, a header file with the following line:
138#       #@INCLUDE_NEXT@ @NEXT_FOO_H@
139# or
140#       #@INCLUDE_NEXT_AS_FIRST_DIRECTIVE@ @NEXT_AS_FIRST_DIRECTIVE_FOO_H@
141# behaves (after sed substitution) as if it contained
142#       #include_next <foo.h>
143# even if the compiler does not support include_next.
144# The three "///" are to pacify Sun C 5.8, which otherwise would say
145# "warning: #include of /usr/include/... may be non-portable".
146# Use '""', not '<>', so that the /// cannot be confused with a C99 comment.
147# Note: This macro assumes that the header file is not empty after
148# preprocessing, i.e. it does not only define preprocessor macros but also
149# provides some type/enum definitions or function/variable declarations.
150#
151# This macro also checks whether each header exists, by invoking
152# AC_CHECK_HEADERS_ONCE or AC_CHECK_HEADERS on each argument.
153AC_DEFUN([gl_CHECK_NEXT_HEADERS],
154[
155  gl_NEXT_HEADERS_INTERNAL([$1], [check])
156])
157
158# gl_NEXT_HEADERS(HEADER1 HEADER2 ...)
159# ------------------------------------
160# Like gl_CHECK_NEXT_HEADERS, except do not check whether the headers exist.
161# This is suitable for headers like <stddef.h> that are standardized by C89
162# and therefore can be assumed to exist.
163AC_DEFUN([gl_NEXT_HEADERS],
164[
165  gl_NEXT_HEADERS_INTERNAL([$1], [assume])
166])
167
168# The guts of gl_CHECK_NEXT_HEADERS and gl_NEXT_HEADERS.
169AC_DEFUN([gl_NEXT_HEADERS_INTERNAL],
170[
171  AC_REQUIRE([gl_INCLUDE_NEXT])
172  AC_REQUIRE([AC_CANONICAL_HOST])
173
174  m4_if([$2], [check],
175    [AC_CHECK_HEADERS_ONCE([$1])
176    ])
177
178dnl FIXME: gl_next_header and gl_header_exists must be used unquoted
179dnl until we can assume autoconf 2.64 or newer.
180  m4_foreach_w([gl_HEADER_NAME], [$1],
181    [AS_VAR_PUSHDEF([gl_next_header],
182                    [gl_cv_next_]m4_defn([gl_HEADER_NAME]))
183     if test $gl_cv_have_include_next = yes; then
184       AS_VAR_SET(gl_next_header, ['<'gl_HEADER_NAME'>'])
185     else
186       AC_CACHE_CHECK(
187         [absolute name of <]m4_defn([gl_HEADER_NAME])[>],
188         m4_defn([gl_next_header]),
189         [m4_if([$2], [check],
190            [AS_VAR_PUSHDEF([gl_header_exists],
191                            [ac_cv_header_]m4_defn([gl_HEADER_NAME]))
192             if test AS_VAR_GET(gl_header_exists) = yes; then
193             AS_VAR_POPDEF([gl_header_exists])
194            ])
195               AC_LANG_CONFTEST(
196                 [AC_LANG_SOURCE(
197                    [[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]]
198                  )])
199               dnl AIX "xlc -E" and "cc -E" omit #line directives for header
200               dnl files that contain only a #include of other header files and
201               dnl no non-comment tokens of their own. This leads to a failure
202               dnl to detect the absolute name of <dirent.h>, <signal.h>,
203               dnl <poll.h> and others. The workaround is to force preservation
204               dnl of comments through option -C. This ensures all necessary
205               dnl #line directives are present. GCC supports option -C as well.
206               case "$host_os" in
207                 aix*) gl_absname_cpp="$ac_cpp -C" ;;
208                 *)    gl_absname_cpp="$ac_cpp" ;;
209               esac
210changequote(,)
211               case "$host_os" in
212                 mingw*)
213                   dnl For the sake of native Windows compilers (excluding gcc),
214                   dnl treat backslash as a directory separator, like /.
215                   dnl Actually, these compilers use a double-backslash as
216                   dnl directory separator, inside the
217                   dnl   # line "filename"
218                   dnl directives.
219                   gl_dirsep_regex='[/\\]'
220                   ;;
221                 *)
222                   gl_dirsep_regex='\/'
223                   ;;
224               esac
225               dnl A sed expression that turns a string into a basic regular
226               dnl expression, for use within "/.../".
227               gl_make_literal_regex_sed='s,[]$^\\.*/[],\\&,g'
228changequote([,])
229               gl_header_literal_regex=`echo ']m4_defn([gl_HEADER_NAME])[' \
230                                        | sed -e "$gl_make_literal_regex_sed"`
231               gl_absolute_header_sed="/${gl_dirsep_regex}${gl_header_literal_regex}/"'{
232                   s/.*"\(.*'"${gl_dirsep_regex}${gl_header_literal_regex}"'\)".*/\1/
233changequote(,)dnl
234                   s|^/[^/]|//&|
235changequote([,])dnl
236                   p
237                   q
238                 }'
239               dnl eval is necessary to expand gl_absname_cpp.
240               dnl Ultrix and Pyramid sh refuse to redirect output of eval,
241               dnl so use subshell.
242               AS_VAR_SET(gl_next_header,
243                 ['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |
244                      sed -n "$gl_absolute_header_sed"`'"'])
245          m4_if([$2], [check],
246            [else
247               AS_VAR_SET(gl_next_header, ['<'gl_HEADER_NAME'>'])
248             fi
249            ])
250         ])
251     fi
252     AC_SUBST(
253       AS_TR_CPP([NEXT_]m4_defn([gl_HEADER_NAME])),
254       [AS_VAR_GET(gl_next_header)])
255     if test $gl_cv_have_include_next = yes || test $gl_cv_have_include_next = buggy; then
256       # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include_next'
257       gl_next_as_first_directive='<'gl_HEADER_NAME'>'
258     else
259       # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include'
260       gl_next_as_first_directive=AS_VAR_GET(gl_next_header)
261     fi
262     AC_SUBST(
263       AS_TR_CPP([NEXT_AS_FIRST_DIRECTIVE_]m4_defn([gl_HEADER_NAME])),
264       [$gl_next_as_first_directive])
265     AS_VAR_POPDEF([gl_next_header])])
266])
267
268# Autoconf 2.68 added warnings for our use of AC_COMPILE_IFELSE;
269# this fallback is safe for all earlier autoconf versions.
270m4_define_default([AC_LANG_DEFINES_PROVIDED])
271