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Fix configure's AC_CHECK_DECLS tests to work correctly with clang.
The test case that Autoconf uses to discover whether a function has been declared doesn't work reliably with clang, because clang reports a warning not an error if the name is a known built-in function. On some platforms, this results in a lot of compile-time warnings about strlcpy and related functions not having been declared. There is a fix for this (by Noah Misch) in the upstream Autoconf sources, but since they've not made a release in years and show no indication of doing so anytime soon, let's just absorb their fix directly. We can revert this when and if we update to a newer Autoconf release. Back-patch to all supported branches. Discussion: https://postgr.es/m/26819.1542515567@sss.pgh.pa.us
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‎aclocal.m4

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@@ -3,6 +3,7 @@ m4_include([config/ac_func_accept_argtypes.m4])
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m4_include([config/acx_pthread.m4])
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m4_include([config/c-compiler.m4])
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m4_include([config/c-library.m4])
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m4_include([config/check_decls.m4])
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m4_include([config/docbook.m4])
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m4_include([config/general.m4])
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m4_include([config/libtool.m4])

‎config/check_decls.m4

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# config/check_decls.m4
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# This file redefines the standard Autoconf macro _AC_CHECK_DECL_BODY,
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# and adds a supporting function _AC_UNDECLARED_WARNING, to make
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# AC_CHECK_DECLS behave correctly when checking for built-in library
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# functions with clang.
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# This is based on commit 82ef7805faffa151e724aa76c245ec590d174580
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# in the Autoconf git repository. We can drop it if they ever get
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# around to releasing a new version of Autoconf. In the meantime,
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# it's distributed under Autoconf's license:
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# This file is part of Autoconf. This program is free
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# software; you can redistribute it and/or modify it under the
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# terms of the GNU General Public License as published by the
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# Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# Under Section 7 of GPL version 3, you are granted additional
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# permissions described in the Autoconf Configure Script Exception,
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# version 3.0, as published by the Free Software Foundation.
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#
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# You should have received a copy of the GNU General Public License
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# and a copy of the Autoconf Configure Script Exception along with
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# this program; see the files COPYINGv3 and COPYING.EXCEPTION
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# respectively. If not, see <http://www.gnu.org/licenses/>.
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# Written by David MacKenzie, with help from
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# Franc,ois Pinard, Karl Berry, Richard Pixley, Ian Lance Taylor,
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# Roland McGrath, Noah Friedman, david d zuhn, and many others.
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# _AC_UNDECLARED_WARNING
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# ----------------------
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# Set ac_[]_AC_LANG_ABBREV[]_decl_warn_flag=yes if the compiler uses a warning,
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# not a more-customary error, to report some undeclared identifiers. Fail when
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# an affected compiler warns also on valid input. _AC_PROG_PREPROC_WORKS_IFELSE
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# solves a related problem.
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AC_DEFUN([_AC_UNDECLARED_WARNING],
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[# The Clang compiler raises a warning for an undeclared identifier that matches
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# a compiler builtin function. All extant Clang versions are affected, as of
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# Clang 3.6.0. Test a builtin known to every version. This problem affects the
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# C and Objective C languages, but Clang does report an error under C++ and
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# Objective C++.
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#
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# Passing -fno-builtin to the compiler would suppress this problem. That
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# strategy would have the advantage of being insensitive to stray warnings, but
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# it would make tests less realistic.
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AC_CACHE_CHECK([how $[]_AC_CC[] reports undeclared, standard C functions],
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[ac_cv_[]_AC_LANG_ABBREV[]_decl_report],
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[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [(void) strchr;])],
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[AS_IF([test -s conftest.err], [dnl
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# For AC_CHECK_DECL to react to warnings, the compiler must be silent on
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# valid AC_CHECK_DECL input. No library function is consistently available
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# on freestanding implementations, so test against a dummy declaration.
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# Include always-available headers on the off chance that they somehow
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# elicit warnings.
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AC_COMPILE_IFELSE([AC_LANG_PROGRAM([dnl
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#include <float.h>
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#include <limits.h>
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#include <stdarg.h>
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#include <stddef.h>
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extern void ac_decl (int, char *);],
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[@%:@ifdef __cplusplus
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(void) ac_decl ((int) 0, (char *) 0);
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(void) ac_decl;
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@%:@else
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(void) ac_decl;
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@%:@endif
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])],
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[AS_IF([test -s conftest.err],
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[AC_MSG_FAILURE([cannot detect from compiler exit status or warnings])],
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[ac_cv_[]_AC_LANG_ABBREV[]_decl_report=warning])],
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[AC_MSG_FAILURE([cannot compile a simple declaration test])])],
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[AC_MSG_FAILURE([compiler does not report undeclared identifiers])])],
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[ac_cv_[]_AC_LANG_ABBREV[]_decl_report=error])])
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case $ac_cv_[]_AC_LANG_ABBREV[]_decl_report in
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warning) ac_[]_AC_LANG_ABBREV[]_decl_warn_flag=yes ;;
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*) ac_[]_AC_LANG_ABBREV[]_decl_warn_flag= ;;
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esac
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])# _AC_UNDECLARED_WARNING
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# _AC_CHECK_DECL_BODY
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# -------------------
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# Shell function body for AC_CHECK_DECL.
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m4_define([_AC_CHECK_DECL_BODY],
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[ AS_LINENO_PUSH([$[]1])
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# Initialize each $ac_[]_AC_LANG_ABBREV[]_decl_warn_flag once.
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AC_DEFUN([_AC_UNDECLARED_WARNING_]_AC_LANG_ABBREV,
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[_AC_UNDECLARED_WARNING])dnl
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AC_REQUIRE([_AC_UNDECLARED_WARNING_]_AC_LANG_ABBREV)dnl
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[as_decl_name=`echo $][2|sed 's/ *(.*//'`]
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[as_decl_use=`echo $][2|sed -e 's/(/((/' -e 's/)/) 0&/' -e 's/,/) 0& (/g'`]
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AC_CACHE_CHECK([whether $as_decl_name is declared], [$[]3],
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[ac_save_werror_flag=$ac_[]_AC_LANG_ABBREV[]_werror_flag
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ac_[]_AC_LANG_ABBREV[]_werror_flag="$ac_[]_AC_LANG_ABBREV[]_decl_warn_flag$ac_[]_AC_LANG_ABBREV[]_werror_flag"
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AC_COMPILE_IFELSE([AC_LANG_PROGRAM([$[]4],
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[@%:@ifndef $[]as_decl_name
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@%:@ifdef __cplusplus
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(void) $[]as_decl_use;
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@%:@else
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(void) $[]as_decl_name;
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@%:@endif
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@%:@endif
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])],
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[AS_VAR_SET([$[]3], [yes])],
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[AS_VAR_SET([$[]3], [no])])
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ac_[]_AC_LANG_ABBREV[]_werror_flag=$ac_save_werror_flag])
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AS_LINENO_POP
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])# _AC_CHECK_DECL_BODY

‎configure

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@@ -2279,13 +2279,16 @@ rm -f conftest.val
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ac_fn_c_check_decl ()
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{
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as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
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as_decl_name=`echo $2|sed 's/ *(.*//'`
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# Initialize each $ac_[]_AC_LANG_ABBREV[]_decl_warn_flag once.
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as_decl_name=`echo $2|sed 's/ *(.*//'`
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as_decl_use=`echo $2|sed -e 's/(/((/' -e 's/)/) 0&/' -e 's/,/) 0& (/g'`
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $as_decl_name is declared" >&5
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$as_echo_n "checking whether $as_decl_name is declared... " >&6; }
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if eval \${$3+:} false; then :
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$as_echo_n "(cached) " >&6
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else
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ac_save_werror_flag=$ac_c_werror_flag
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ac_c_werror_flag="$ac_c_decl_warn_flag$ac_c_werror_flag"
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cat confdefs.h - <<_ACEOF >conftest.$ac_ext
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/* end confdefs.h. */
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$4
@@ -2310,6 +2313,7 @@ else
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eval "$3=no"
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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ac_c_werror_flag=$ac_save_werror_flag
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fi
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eval ac_res=\$$3
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
@@ -11764,7 +11768,96 @@ esac
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# posix_fadvise() is a no-op on Solaris, so don't incur function overhead
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# by calling it, 2009-04-02
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# http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/lib/libc/port/gen/posix_fadvise.c
11767-
if test "$PORTNAME" != "solaris"; then
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# The Clang compiler raises a warning for an undeclared identifier that matches
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# a compiler builtin function. All extant Clang versions are affected, as of
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# Clang 3.6.0. Test a builtin known to every version. This problem affects the
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# C and Objective C languages, but Clang does report an error under C++ and
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# Objective C++.
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#
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# Passing -fno-builtin to the compiler would suppress this problem. That
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# strategy would have the advantage of being insensitive to stray warnings, but
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# it would make tests less realistic.
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking how $CC reports undeclared, standard C functions" >&5
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$as_echo_n "checking how $CC reports undeclared, standard C functions... " >&6; }
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if ${ac_cv_c_decl_report+:} false; then :
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$as_echo_n "(cached) " >&6
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else
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cat confdefs.h - <<_ACEOF >conftest.$ac_ext
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/* end confdefs.h. */
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int
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main ()
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{
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(void) strchr;
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;
11793+
return 0;
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}
11795+
_ACEOF
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if ac_fn_c_try_compile "$LINENO"; then :
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if test -s conftest.err; then :
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# For AC_CHECK_DECL to react to warnings, the compiler must be silent on
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# valid AC_CHECK_DECL input. No library function is consistently available
11800+
# on freestanding implementations, so test against a dummy declaration.
11801+
# Include always-available headers on the off chance that they somehow
11802+
# elicit warnings.
11803+
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
11804+
/* end confdefs.h. */
11805+
#include <float.h>
11806+
#include <limits.h>
11807+
#include <stdarg.h>
11808+
#include <stddef.h>
11809+
extern void ac_decl (int, char *);
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int
11811+
main ()
11812+
{
11813+
#ifdef __cplusplus
11814+
(void) ac_decl ((int) 0, (char *) 0);
11815+
(void) ac_decl;
11816+
#else
11817+
(void) ac_decl;
11818+
#endif
11819+
11820+
;
11821+
return 0;
11822+
}
11823+
_ACEOF
11824+
if ac_fn_c_try_compile "$LINENO"; then :
11825+
if test -s conftest.err; then :
11826+
{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
11827+
$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
11828+
as_fn_error $? "cannot detect from compiler exit status or warnings
11829+
See \`config.log' for more details" "$LINENO" 5; }
11830+
else
11831+
ac_cv_c_decl_report=warning
11832+
fi
11833+
else
11834+
{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
11835+
$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
11836+
as_fn_error $? "cannot compile a simple declaration test
11837+
See \`config.log' for more details" "$LINENO" 5; }
11838+
fi
11839+
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
11840+
else
11841+
{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
11842+
$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
11843+
as_fn_error $? "compiler does not report undeclared identifiers
11844+
See \`config.log' for more details" "$LINENO" 5; }
11845+
fi
11846+
else
11847+
ac_cv_c_decl_report=error
11848+
fi
11849+
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
11850+
fi
11851+
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_c_decl_report" >&5
11852+
$as_echo "$ac_cv_c_decl_report" >&6; }
11853+
11854+
case $ac_cv_c_decl_report in
11855+
warning) ac_c_decl_warn_flag=yes ;;
11856+
*) ac_c_decl_warn_flag= ;;
11857+
esac
11858+
11859+
if test "$PORTNAME" != "solaris"; then :
11860+
1176811861
for ac_func in posix_fadvise
1176911862
do :
1177011863
ac_fn_c_check_func "$LINENO" "posix_fadvise" "ac_cv_func_posix_fadvise"
@@ -11788,7 +11881,8 @@ cat >>confdefs.h <<_ACEOF
1178811881
#define HAVE_DECL_POSIX_FADVISE $ac_have_decl
1178911882
_ACEOF
1179011883

11791-
fi
11884+
11885+
fi # fi
1179211886

1179311887
ac_fn_c_check_decl "$LINENO" "fdatasync" "ac_cv_have_decl_fdatasync" "#include <unistd.h>
1179411888
"

‎configure.in

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1373,10 +1373,11 @@ esac
13731373
# posix_fadvise() is a no-op on Solaris, so don't incur function overhead
13741374
# by calling it, 2009-04-02
13751375
# http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/lib/libc/port/gen/posix_fadvise.c
1376-
if test "$PORTNAME" != "solaris"; then
1376+
dnl must use AS_IF here, else AC_REQUIRES inside AC_CHECK_DECLS malfunctions
1377+
AS_IF([test "$PORTNAME" != "solaris"], [
13771378
AC_CHECK_FUNCS(posix_fadvise)
13781379
AC_CHECK_DECLS(posix_fadvise, [], [], [#include <fcntl.h>])
1379-
fi
1380+
]) # fi
13801381

13811382
AC_CHECK_DECLS(fdatasync, [], [], [#include <unistd.h>])
13821383
AC_CHECK_DECLS([strlcat, strlcpy])

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