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Commit97b398e

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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 hasbeen declared doesn't work reliably with clang, because clang reportsa 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 aboutstrlcpy 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 ofdoing so anytime soon, let's just absorb their fix directly. We canrevert 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
1 parent85efd1a commit97b398e

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4 files changed

+217
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4 files changed

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‎aclocal.m4

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Original file line numberDiff line numberDiff line change
@@ -4,6 +4,7 @@ m4_include([config/ax_prog_perl_modules.m4])
44
m4_include([config/ax_pthread.m4])
55
m4_include([config/c-compiler.m4])
66
m4_include([config/c-library.m4])
7+
m4_include([config/check_decls.m4])
78
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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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,116 @@
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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])])
82+
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case $ac_cv_[]_AC_LANG_ABBREV[]_decl_report in
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warning) ac_[]_AC_LANG_ABBREV[]_decl_warn_flag=yes ;;
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*) ac_[]_AC_LANG_ABBREV[]_decl_warn_flag= ;;
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esac
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])# _AC_UNDECLARED_WARNING
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# _AC_CHECK_DECL_BODY
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# -------------------
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# Shell function body for AC_CHECK_DECL.
92+
m4_define([_AC_CHECK_DECL_BODY],
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[ AS_LINENO_PUSH([$[]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) $[]as_decl_name;
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@%:@endif
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@%:@endif
111+
])],
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[AS_VAR_SET([$[]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

Lines changed: 97 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2304,13 +2304,16 @@ rm -f conftest.val
23042304
ac_fn_c_check_decl ()
23052305
{
23062306
as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
2307-
as_decl_name=`echo$2|sed's/ *(.*//'`
2307+
# Initialize each $ac_[]_AC_LANG_ABBREV[]_decl_warn_flag once.
2308+
as_decl_name=`echo$2|sed's/ *(.*//'`
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as_decl_use=`echo$2|sed -e's/(/((/' -e's/)/) 0&/' -e's/,/) 0& (/g'`
23092310
{$as_echo"$as_me:${as_lineno-$LINENO}: checking whether$as_decl_name is declared">&5
23102311
$as_echo_n"checking whether$as_decl_name is declared...">&6; }
23112312
ifeval\${$3+:}false;then:
23122313
$as_echo_n"(cached)">&6
23132314
else
2315+
ac_save_werror_flag=$ac_c_werror_flag
2316+
ac_c_werror_flag="$ac_c_decl_warn_flag$ac_c_werror_flag"
23142317
cat confdefs.h -<<_ACEOF >conftest.$ac_ext
23152318
/* end confdefs.h. */
23162319
$4
@@ -2335,6 +2338,7 @@ else
23352338
eval"$3=no"
23362339
fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
2341+
ac_c_werror_flag=$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:$ac_res">&5
@@ -13262,7 +13266,96 @@ esac
1326213266
# posix_fadvise() is a no-op on Solaris, so don't incur function overhead
1326313267
# by calling it, 2009-04-02
1326413268
# http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/lib/libc/port/gen/posix_fadvise.c
13265-
iftest"$PORTNAME"!="solaris";then
13269+
# The Clang compiler raises a warning for an undeclared identifier that matches
13270+
# a compiler builtin function. All extant Clang versions are affected, as of
13271+
# Clang 3.6.0. Test a builtin known to every version. This problem affects the
13272+
# C and Objective C languages, but Clang does report an error under C++ and
13273+
# Objective C++.
13274+
#
13275+
# Passing -fno-builtin to the compiler would suppress this problem. That
13276+
# strategy would have the advantage of being insensitive to stray warnings, but
13277+
# it would make tests less realistic.
13278+
{$as_echo"$as_me:${as_lineno-$LINENO}: checking how$CC reports undeclared, standard C functions">&5
13279+
$as_echo_n"checking how$CC reports undeclared, standard C functions...">&6; }
13280+
if${ac_cv_c_decl_report+:}false;then:
13281+
$as_echo_n"(cached)">&6
13282+
else
13283+
cat confdefs.h -<<_ACEOF >conftest.$ac_ext
13284+
/* end confdefs.h. */
13285+
13286+
int
13287+
main ()
13288+
{
13289+
(void) strchr;
13290+
;
13291+
return 0;
13292+
}
13293+
_ACEOF
13294+
if ac_fn_c_try_compile"$LINENO";then:
13295+
iftest -s conftest.err;then:
13296+
# For AC_CHECK_DECL to react to warnings, the compiler must be silent on
13297+
# valid AC_CHECK_DECL input. No library function is consistently available
13298+
# on freestanding implementations, so test against a dummy declaration.
13299+
# Include always-available headers on the off chance that they somehow
13300+
# elicit warnings.
13301+
cat confdefs.h -<<_ACEOF >conftest.$ac_ext
13302+
/* end confdefs.h. */
13303+
#include <float.h>
13304+
#include <limits.h>
13305+
#include <stdarg.h>
13306+
#include <stddef.h>
13307+
extern void ac_decl (int, char *);
13308+
int
13309+
main ()
13310+
{
13311+
#ifdef __cplusplus
13312+
(void) ac_decl ((int) 0, (char *) 0);
13313+
(void) ac_decl;
13314+
#else
13315+
(void) ac_decl;
13316+
#endif
13317+
13318+
;
13319+
return 0;
13320+
}
13321+
_ACEOF
13322+
if ac_fn_c_try_compile"$LINENO";then:
13323+
iftest -s conftest.err;then:
13324+
{ {$as_echo"$as_me:${as_lineno-$LINENO}: error: in\`$ac_pwd':">&5
13325+
$as_echo"$as_me: error: in\`$ac_pwd':">&2;}
13326+
as_fn_error$?"cannot detect from compiler exit status or warnings
13327+
See\`config.log' for more details""$LINENO" 5; }
13328+
else
13329+
ac_cv_c_decl_report=warning
13330+
fi
13331+
else
13332+
{ {$as_echo"$as_me:${as_lineno-$LINENO}: error: in\`$ac_pwd':">&5
13333+
$as_echo"$as_me: error: in\`$ac_pwd':">&2;}
13334+
as_fn_error$?"cannot compile a simple declaration test
13335+
See\`config.log' for more details""$LINENO" 5; }
13336+
fi
13337+
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
13338+
else
13339+
{ {$as_echo"$as_me:${as_lineno-$LINENO}: error: in\`$ac_pwd':">&5
13340+
$as_echo"$as_me: error: in\`$ac_pwd':">&2;}
13341+
as_fn_error$?"compiler does not report undeclared identifiers
13342+
See\`config.log' for more details""$LINENO" 5; }
13343+
fi
13344+
else
13345+
ac_cv_c_decl_report=error
13346+
fi
13347+
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
13348+
fi
13349+
{$as_echo"$as_me:${as_lineno-$LINENO}: result:$ac_cv_c_decl_report">&5
13350+
$as_echo"$ac_cv_c_decl_report">&6; }
13351+
13352+
case$ac_cv_c_decl_reportin
13353+
warning) ac_c_decl_warn_flag=yes ;;
13354+
*) ac_c_decl_warn_flag= ;;
13355+
esac
13356+
13357+
iftest"$PORTNAME"!="solaris";then:
13358+
1326613359
forac_funcin posix_fadvise
1326713360
do:
1326813361
ac_fn_c_check_func"$LINENO""posix_fadvise""ac_cv_func_posix_fadvise"
@@ -13286,7 +13379,8 @@ cat >>confdefs.h <<_ACEOF
1328613379
#define HAVE_DECL_POSIX_FADVISE$ac_have_decl
1328713380
_ACEOF
1328813381

13289-
fi
13382+
13383+
fi# fi
1329013384

1329113385
ac_fn_c_check_decl"$LINENO""fdatasync""ac_cv_have_decl_fdatasync""#include <unistd.h>
1329213386
"

‎configure.in

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1492,10 +1492,11 @@ esac
14921492
# posix_fadvise() is a no-op on Solaris, so don't incur function overhead
14931493
# by calling it, 2009-04-02
14941494
# http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/lib/libc/port/gen/posix_fadvise.c
1495-
if test "$PORTNAME" != "solaris"; then
1495+
dnl must use AS_IF here, else AC_REQUIRES inside AC_CHECK_DECLS malfunctions
1496+
AS_IF([test "$PORTNAME" != "solaris"], [
14961497
AC_CHECK_FUNCS(posix_fadvise)
14971498
AC_CHECK_DECLS(posix_fadvise, [], [], [#include <fcntl.h>])
1498-
fi
1499+
]) #fi
14991500

15001501
AC_CHECK_DECLS(fdatasync, [], [], [#include <unistd.h>])
15011502
AC_CHECK_DECLS([strlcat, strlcpy])

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