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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
This commit is contained in:
Tom Lane
104
configure
vendored
104
configure
vendored
@ -1756,13 +1756,16 @@ fi
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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
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@ -1787,6 +1790,7 @@ 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: $ac_res" >&5
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@ -4990,11 +4994,100 @@ fi
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test -n "$AWK" && break
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done
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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.$ac_ext
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/* end confdefs.h. */
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int
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main ()
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{
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(void) strchr;
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;
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return 0;
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}
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_ACEOF
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if ac_fn_c_try_compile "$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
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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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cat confdefs.h - <<_ACEOF >conftest.$ac_ext
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/* end confdefs.h. */
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#include <float.h>
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#include <limits.h>
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#include <stdarg.h>
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#include <stddef.h>
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extern void ac_decl (int, char *);
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int
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main ()
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{
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#ifdef __cplusplus
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(void) ac_decl ((int) 0, (char *) 0);
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(void) ac_decl;
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#else
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(void) ac_decl;
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#endif
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;
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return 0;
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}
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_ACEOF
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if ac_fn_c_try_compile "$LINENO"; then :
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if test -s conftest.err; then :
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{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
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$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
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as_fn_error $? "cannot detect from compiler exit status or warnings
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See \`config.log' for more details" "$LINENO" 5; }
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else
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ac_cv_c_decl_report=warning
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fi
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else
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{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
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$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
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as_fn_error $? "cannot compile a simple declaration test
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See \`config.log' for more details" "$LINENO" 5; }
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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else
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{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
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$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
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as_fn_error $? "compiler does not report undeclared identifiers
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See \`config.log' for more details" "$LINENO" 5; }
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fi
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else
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ac_cv_c_decl_report=error
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_c_decl_report" >&5
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$as_echo "$ac_cv_c_decl_report" >&6; }
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case $ac_cv_c_decl_report in
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warning) ac_c_decl_warn_flag=yes ;;
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*) ac_c_decl_warn_flag= ;;
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esac
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if test "$with_llvm" = yes; then :
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if test -z "$LLVM_CONFIG"; then
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for ac_prog in llvm-config llvm-config-7 llvm-config-6.0 llvm-config-5.0 llvm-config-4.0 llvm-config-3.9
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do
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@ -5250,7 +5343,8 @@ _ACEOF
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fi
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fi # fi
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unset CFLAGS
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@ -15197,7 +15291,8 @@ esac
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# posix_fadvise() is a no-op on Solaris, so don't incur function overhead
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# by calling it, 2009-04-02
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# http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/lib/libc/port/gen/posix_fadvise.c
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if test "$PORTNAME" != "solaris"; then
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if test "$PORTNAME" != "solaris"; then :
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for ac_func in posix_fadvise
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do :
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ac_fn_c_check_func "$LINENO" "posix_fadvise" "ac_cv_func_posix_fadvise"
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@ -15221,7 +15316,8 @@ cat >>confdefs.h <<_ACEOF
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#define HAVE_DECL_POSIX_FADVISE $ac_have_decl
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_ACEOF
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fi
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fi # fi
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ac_fn_c_check_decl "$LINENO" "fdatasync" "ac_cv_have_decl_fdatasync" "#include <unistd.h>
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"
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