1# include_next.m4 serial 14
2dnl Copyright (C) 2006-2009 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__'.
27
28AC_DEFUN([gl_INCLUDE_NEXT],
29[
30  AC_LANG_PREPROC_REQUIRE()
31  AC_CACHE_CHECK([whether the preprocessor supports include_next],
32    [gl_cv_have_include_next],
33    [rm -rf conftestd1a conftestd1b conftestd2
34     mkdir conftestd1a conftestd1b conftestd2
35     dnl IBM C 9.0, 10.1 (original versions, prior to the 2009-01 updates) on
36     dnl AIX 6.1 support include_next when used as first preprocessor directive
37     dnl in a file, but not when preceded by another include directive. Check
38     dnl for this bug by including <stdio.h>.
39     dnl Additionally, with this same compiler, include_next is a no-op when
40     dnl used in a header file that was included by specifying its absolute
41     dnl file name. Despite these two bugs, include_next is used in the
42     dnl compiler's <math.h>. By virtue of the second bug, we need to use
43     dnl include_next as well in this case.
44     cat <<EOF > conftestd1a/conftest.h
45#define DEFINED_IN_CONFTESTD1
46#include_next <conftest.h>
47#ifdef DEFINED_IN_CONFTESTD2
48int foo;
49#else
50#error "include_next doesn't work"
51#endif
52EOF
53     cat <<EOF > conftestd1b/conftest.h
54#define DEFINED_IN_CONFTESTD1
55#include <stdio.h>
56#include_next <conftest.h>
57#ifdef DEFINED_IN_CONFTESTD2
58int foo;
59#else
60#error "include_next doesn't work"
61#endif
62EOF
63     cat <<EOF > conftestd2/conftest.h
64#ifndef DEFINED_IN_CONFTESTD1
65#error "include_next test doesn't work"
66#endif
67#define DEFINED_IN_CONFTESTD2
68EOF
69     gl_save_CPPFLAGS="$CPPFLAGS"
70     CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2"
71     AC_COMPILE_IFELSE([#include <conftest.h>],
72       [gl_cv_have_include_next=yes],
73       [CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2"
74        AC_COMPILE_IFELSE([#include <conftest.h>],
75          [gl_cv_have_include_next=buggy],
76          [gl_cv_have_include_next=no])
77       ])
78     CPPFLAGS="$gl_save_CPPFLAGS"
79     rm -rf conftestd1a conftestd1b conftestd2
80    ])
81  PRAGMA_SYSTEM_HEADER=
82  if test $gl_cv_have_include_next = yes; then
83    INCLUDE_NEXT=include_next
84    INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
85    if test -n "$GCC"; then
86      PRAGMA_SYSTEM_HEADER='#pragma GCC system_header'
87    fi
88  else
89    if test $gl_cv_have_include_next = buggy; then
90      INCLUDE_NEXT=include
91      INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
92    else
93      INCLUDE_NEXT=include
94      INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include
95    fi
96  fi
97  AC_SUBST([INCLUDE_NEXT])
98  AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE])
99  AC_SUBST([PRAGMA_SYSTEM_HEADER])
100])
101
102# gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...)
103# ------------------------------------------
104# For each arg foo.h, if #include_next works, define NEXT_FOO_H to be
105# '<foo.h>'; otherwise define it to be
106# '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
107# Also, if #include_next works as first preprocessing directive in a file,
108# define NEXT_AS_FIRST_DIRECTIVE_FOO_H to be '<foo.h>'; otherwise define it to
109# be
110# '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
111# That way, a header file with the following line:
112#	#@INCLUDE_NEXT@ @NEXT_FOO_H@
113# or
114#	#@INCLUDE_NEXT_AS_FIRST_DIRECTIVE@ @NEXT_AS_FIRST_DIRECTIVE_FOO_H@
115# behaves (after sed substitution) as if it contained
116#	#include_next <foo.h>
117# even if the compiler does not support include_next.
118# The three "///" are to pacify Sun C 5.8, which otherwise would say
119# "warning: #include of /usr/include/... may be non-portable".
120# Use `""', not `<>', so that the /// cannot be confused with a C99 comment.
121# Note: This macro assumes that the header file is not empty after
122# preprocessing, i.e. it does not only define preprocessor macros but also
123# provides some type/enum definitions or function/variable declarations.
124AC_DEFUN([gl_CHECK_NEXT_HEADERS],
125[
126  AC_REQUIRE([gl_INCLUDE_NEXT])
127  AC_REQUIRE([AC_CANONICAL_HOST])
128  AC_CHECK_HEADERS_ONCE([$1])
129
130  m4_foreach_w([gl_HEADER_NAME], [$1],
131    [AS_VAR_PUSHDEF([gl_next_header],
132		    [gl_cv_next_]m4_defn([gl_HEADER_NAME]))
133     if test $gl_cv_have_include_next = yes; then
134       AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
135     else
136       AC_CACHE_CHECK(
137	 [absolute name of <]m4_defn([gl_HEADER_NAME])[>],
138	 m4_defn([gl_next_header]),
139	 [AS_VAR_PUSHDEF([gl_header_exists],
140			 [ac_cv_header_]m4_defn([gl_HEADER_NAME]))
141	  if test AS_VAR_GET(gl_header_exists) = yes; then
142	    AC_LANG_CONFTEST(
143	      [AC_LANG_SOURCE(
144		 [[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]]
145	       )])
146	    dnl AIX "xlc -E" and "cc -E" omit #line directives for header files
147	    dnl that contain only a #include of other header files and no
148	    dnl non-comment tokens of their own. This leads to a failure to
149	    dnl detect the absolute name of <dirent.h>, <signal.h>, <poll.h>
150	    dnl and others. The workaround is to force preservation of comments
151	    dnl through option -C. This ensures all necessary #line directives
152	    dnl are present. GCC supports option -C as well.
153	    case "$host_os" in
154	      aix*) gl_absname_cpp="$ac_cpp -C" ;;
155	      *)    gl_absname_cpp="$ac_cpp" ;;
156	    esac
157	    dnl eval is necessary to expand gl_absname_cpp.
158	    dnl Ultrix and Pyramid sh refuse to redirect output of eval,
159	    dnl so use subshell.
160	    AS_VAR_SET([gl_next_header],
161	      ['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |
162	       sed -n '\#/]m4_defn([gl_HEADER_NAME])[#{
163		 s#.*"\(.*/]m4_defn([gl_HEADER_NAME])[\)".*#\1#
164		 s#^/[^/]#//&#
165		 p
166		 q
167	       }'`'"'])
168	  else
169	    AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
170	  fi
171	  AS_VAR_POPDEF([gl_header_exists])])
172     fi
173     AC_SUBST(
174       AS_TR_CPP([NEXT_]m4_defn([gl_HEADER_NAME])),
175       [AS_VAR_GET([gl_next_header])])
176     if test $gl_cv_have_include_next = yes || test $gl_cv_have_include_next = buggy; then
177       # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include_next'
178       gl_next_as_first_directive='<'gl_HEADER_NAME'>'
179     else
180       # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include'
181       gl_next_as_first_directive=AS_VAR_GET([gl_next_header])
182     fi
183     AC_SUBST(
184       AS_TR_CPP([NEXT_AS_FIRST_DIRECTIVE_]m4_defn([gl_HEADER_NAME])),
185       [$gl_next_as_first_directive])
186     AS_VAR_POPDEF([gl_next_header])])
187])
188