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Fix configure's AC_CHECK_DECLS tests to work correctly with clang.

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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
This commit is contained in:
Tom Lane
2018-11-19 12:01:47 -05:00
parent 85efd1a041
commit 97b398ee5c
4 changed files with 217 additions and 5 deletions
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100
configure vendored
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@ -2304,13 +2304,16 @@ rm -f conftest.val
ac_fn_c_check_decl ()
{
as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
as_decl_name=`echo $2|sed 's/ *(.*//'`
# Initialize each $ac_[]_AC_LANG_ABBREV[]_decl_warn_flag once.
as_decl_name=`echo $2|sed 's/ *(.*//'`
as_decl_use=`echo $2|sed -e 's/(/((/' -e 's/)/) 0&/' -e 's/,/) 0& (/g'`
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $as_decl_name is declared" >&5
$as_echo_n "checking whether $as_decl_name is declared... " >&6; }
if eval \${$3+:} false; then :
$as_echo_n "(cached) " >&6
else
ac_save_werror_flag=$ac_c_werror_flag
ac_c_werror_flag="$ac_c_decl_warn_flag$ac_c_werror_flag"
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
$4
@ -2335,6 +2338,7 @@ else
eval "$3=no"
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
ac_c_werror_flag=$ac_save_werror_flag
fi
eval ac_res=\$$3
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
@ -13262,7 +13266,96 @@ esac
# posix_fadvise() is a no-op on Solaris, so don't incur function overhead
# by calling it, 2009-04-02
# http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/lib/libc/port/gen/posix_fadvise.c
if test "$PORTNAME" != "solaris"; then
# The Clang compiler raises a warning for an undeclared identifier that matches
# a compiler builtin function. All extant Clang versions are affected, as of
# Clang 3.6.0. Test a builtin known to every version. This problem affects the
# C and Objective C languages, but Clang does report an error under C++ and
# Objective C++.
#
# Passing -fno-builtin to the compiler would suppress this problem. That
# strategy would have the advantage of being insensitive to stray warnings, but
# it would make tests less realistic.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking how $CC reports undeclared, standard C functions" >&5
$as_echo_n "checking how $CC reports undeclared, standard C functions... " >&6; }
if ${ac_cv_c_decl_report+:} false; then :
$as_echo_n "(cached) " >&6
else
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
int
main ()
{
(void) strchr;
;
return 0;
}
_ACEOF
if ac_fn_c_try_compile "$LINENO"; then :
if test -s conftest.err; then :
# For AC_CHECK_DECL to react to warnings, the compiler must be silent on
# valid AC_CHECK_DECL input. No library function is consistently available
# on freestanding implementations, so test against a dummy declaration.
# Include always-available headers on the off chance that they somehow
# elicit warnings.
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <float.h>
#include <limits.h>
#include <stdarg.h>
#include <stddef.h>
extern void ac_decl (int, char *);
int
main ()
{
#ifdef __cplusplus
(void) ac_decl ((int) 0, (char *) 0);
(void) ac_decl;
#else
(void) ac_decl;
#endif
;
return 0;
}
_ACEOF
if ac_fn_c_try_compile "$LINENO"; then :
if test -s conftest.err; then :
{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
as_fn_error $? "cannot detect from compiler exit status or warnings
See \`config.log' for more details" "$LINENO" 5; }
else
ac_cv_c_decl_report=warning
fi
else
{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
as_fn_error $? "cannot compile a simple declaration test
See \`config.log' for more details" "$LINENO" 5; }
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
else
{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
as_fn_error $? "compiler does not report undeclared identifiers
See \`config.log' for more details" "$LINENO" 5; }
fi
else
ac_cv_c_decl_report=error
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_c_decl_report" >&5
$as_echo "$ac_cv_c_decl_report" >&6; }
case $ac_cv_c_decl_report in
warning) ac_c_decl_warn_flag=yes ;;
*) ac_c_decl_warn_flag= ;;
esac
if test "$PORTNAME" != "solaris"; then :
for ac_func in posix_fadvise
do :
ac_fn_c_check_func "$LINENO" "posix_fadvise" "ac_cv_func_posix_fadvise"
@ -13286,7 +13379,8 @@ cat >>confdefs.h <<_ACEOF
#define HAVE_DECL_POSIX_FADVISE $ac_have_decl
_ACEOF
fi
fi # fi
ac_fn_c_check_decl "$LINENO" "fdatasync" "ac_cv_have_decl_fdatasync" "#include <unistd.h>
"