Remove configure-time thread safety checking (thread_test.c).

This testing was useful when it was written, nigh twenty years ago,
but it seems fairly pointless for any platform built in the last
dozen or more years.  (Compare also the comments at 8a212118.)
Also we now have reports that the test program itself fails under
ThreadSanitizer.  Rather than invest effort in fixing it, let's
just drop it, and assume that the few people who still care
already know they need to use --disable-thread-safety.

Back-patch into v14, for consistency with 8a212118.

Discussion: https://postgr.es/m/CADhDkKzPSiNvA3Hyq+wSR_icuPmazG0cFe=YnC3U-CFcYLc8Xw@mail.gmail.com

configure

@@ -11934,10 +11934,10 @@ if test "$ac_res" != no; then :
 
 fi
 
-# Required for thread_test.c on Solaris
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing sched_yield" >&5
-$as_echo_n "checking for library containing sched_yield... " >&6; }
-if ${ac_cv_search_sched_yield+:} false; then :
+# Cygwin:
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing shmget" >&5
+$as_echo_n "checking for library containing shmget... " >&6; }
+if ${ac_cv_search_shmget+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   ac_func_search_save_LIBS=$LIBS
@@ -11950,16 +11950,16 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 #ifdef __cplusplus
 extern "C"
 #endif
-char sched_yield ();
+char shmget ();
 int
 main ()
 {
-return sched_yield ();
+return shmget ();
   ;
   return 0;
 }
 _ACEOF
-for ac_lib in '' rt; do
+for ac_lib in '' cygipc; do
   if test -z "$ac_lib"; then
     ac_res="none required"
   else
@@ -11967,35 +11967,34 @@ for ac_lib in '' rt; do
     LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
   fi
   if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_search_sched_yield=$ac_res
+  ac_cv_search_shmget=$ac_res
 fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext
-  if ${ac_cv_search_sched_yield+:} false; then :
+  if ${ac_cv_search_shmget+:} false; then :
   break
 fi
 done
-if ${ac_cv_search_sched_yield+:} false; then :
+if ${ac_cv_search_shmget+:} false; then :
 
 else
-  ac_cv_search_sched_yield=no
+  ac_cv_search_shmget=no
 fi
 rm conftest.$ac_ext
 LIBS=$ac_func_search_save_LIBS
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_sched_yield" >&5
-$as_echo "$ac_cv_search_sched_yield" >&6; }
-ac_res=$ac_cv_search_sched_yield
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_shmget" >&5
+$as_echo "$ac_cv_search_shmget" >&6; }
+ac_res=$ac_cv_search_shmget
 if test "$ac_res" != no; then :
   test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
 
 fi
 
-# Required for thread_test.c on Solaris 2.5:
-# Other ports use it too (HP-UX) so test unconditionally
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing gethostbyname_r" >&5
-$as_echo_n "checking for library containing gethostbyname_r... " >&6; }
-if ${ac_cv_search_gethostbyname_r+:} false; then :
+# *BSD:
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing backtrace_symbols" >&5
+$as_echo_n "checking for library containing backtrace_symbols... " >&6; }
+if ${ac_cv_search_backtrace_symbols+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   ac_func_search_save_LIBS=$LIBS
@@ -12008,16 +12007,16 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 #ifdef __cplusplus
 extern "C"
 #endif
-char gethostbyname_r ();
+char backtrace_symbols ();
 int
 main ()
 {
-return gethostbyname_r ();
+return backtrace_symbols ();
   ;
   return 0;
 }
 _ACEOF
-for ac_lib in '' nsl; do
+for ac_lib in '' execinfo; do
   if test -z "$ac_lib"; then
     ac_res="none required"
   else
@@ -12025,91 +12024,35 @@ for ac_lib in '' nsl; do
     LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
   fi
   if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_search_gethostbyname_r=$ac_res
+  ac_cv_search_backtrace_symbols=$ac_res
 fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext
-  if ${ac_cv_search_gethostbyname_r+:} false; then :
+  if ${ac_cv_search_backtrace_symbols+:} false; then :
   break
 fi
 done
-if ${ac_cv_search_gethostbyname_r+:} false; then :
+if ${ac_cv_search_backtrace_symbols+:} false; then :
 
 else
-  ac_cv_search_gethostbyname_r=no
+  ac_cv_search_backtrace_symbols=no
 fi
 rm conftest.$ac_ext
 LIBS=$ac_func_search_save_LIBS
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_gethostbyname_r" >&5
-$as_echo "$ac_cv_search_gethostbyname_r" >&6; }
-ac_res=$ac_cv_search_gethostbyname_r
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_backtrace_symbols" >&5
+$as_echo "$ac_cv_search_backtrace_symbols" >&6; }
+ac_res=$ac_cv_search_backtrace_symbols
 if test "$ac_res" != no; then :
   test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
 
 fi
 
-# Cygwin:
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing shmget" >&5
-$as_echo_n "checking for library containing shmget... " >&6; }
-if ${ac_cv_search_shmget+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  ac_func_search_save_LIBS=$LIBS
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
 
-/* Override any GCC internal prototype to avoid an error.
-   Use char because int might match the return type of a GCC
-   builtin and then its argument prototype would still apply.  */
-#ifdef __cplusplus
-extern "C"
-#endif
-char shmget ();
-int
-main ()
-{
-return shmget ();
-  ;
-  return 0;
-}
-_ACEOF
-for ac_lib in '' cygipc; do
-  if test -z "$ac_lib"; then
-    ac_res="none required"
-  else
-    ac_res=-l$ac_lib
-    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
-  fi
-  if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_search_shmget=$ac_res
-fi
-rm -f core conftest.err conftest.$ac_objext \
-    conftest$ac_exeext
-  if ${ac_cv_search_shmget+:} false; then :
-  break
-fi
-done
-if ${ac_cv_search_shmget+:} false; then :
-
-else
-  ac_cv_search_shmget=no
-fi
-rm conftest.$ac_ext
-LIBS=$ac_func_search_save_LIBS
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_shmget" >&5
-$as_echo "$ac_cv_search_shmget" >&6; }
-ac_res=$ac_cv_search_shmget
-if test "$ac_res" != no; then :
-  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
-
-fi
-
-# *BSD:
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing backtrace_symbols" >&5
-$as_echo_n "checking for library containing backtrace_symbols... " >&6; }
-if ${ac_cv_search_backtrace_symbols+:} false; then :
+if test "$enable_thread_safety" = yes; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing gethostbyname_r" >&5
+$as_echo_n "checking for library containing gethostbyname_r... " >&6; }
+if ${ac_cv_search_gethostbyname_r+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   ac_func_search_save_LIBS=$LIBS
@@ -12122,16 +12065,16 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 #ifdef __cplusplus
 extern "C"
 #endif
-char backtrace_symbols ();
+char gethostbyname_r ();
 int
 main ()
 {
-return backtrace_symbols ();
+return gethostbyname_r ();
   ;
   return 0;
 }
 _ACEOF
-for ac_lib in '' execinfo; do
+for ac_lib in '' nsl; do
   if test -z "$ac_lib"; then
     ac_res="none required"
   else
@@ -12139,32 +12082,30 @@ for ac_lib in '' execinfo; do
     LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
   fi
   if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_search_backtrace_symbols=$ac_res
+  ac_cv_search_gethostbyname_r=$ac_res
 fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext
-  if ${ac_cv_search_backtrace_symbols+:} false; then :
+  if ${ac_cv_search_gethostbyname_r+:} false; then :
   break
 fi
 done
-if ${ac_cv_search_backtrace_symbols+:} false; then :
+if ${ac_cv_search_gethostbyname_r+:} false; then :
 
 else
-  ac_cv_search_backtrace_symbols=no
+  ac_cv_search_gethostbyname_r=no
 fi
 rm conftest.$ac_ext
 LIBS=$ac_func_search_save_LIBS
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_backtrace_symbols" >&5
-$as_echo "$ac_cv_search_backtrace_symbols" >&6; }
-ac_res=$ac_cv_search_backtrace_symbols
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_gethostbyname_r" >&5
+$as_echo "$ac_cv_search_gethostbyname_r" >&6; }
+ac_res=$ac_cv_search_gethostbyname_r
 if test "$ac_res" != no; then :
   test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
 
 fi
 
-
-if test "$enable_thread_safety" = yes; then
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing pthread_barrier_wait" >&5
 $as_echo_n "checking for library containing pthread_barrier_wait... " >&6; }
 if ${ac_cv_search_pthread_barrier_wait+:} false; then :
@@ -19393,57 +19334,6 @@ fi
   fi
 fi
 
-# Thread testing
-
-# We have to run the thread test near the end so we have all our symbols
-# defined.  Cross compiling throws a warning.
-#
-if test "$enable_thread_safety" = yes; then
-if test "$PORTNAME" != "win32"
-then
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking thread safety of required library functions" >&5
-$as_echo_n "checking thread safety of required library functions... " >&6; }
-
-_CFLAGS="$CFLAGS"
-_LIBS="$LIBS"
-CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
-LIBS="$LIBS $PTHREAD_LIBS"
-if test "$cross_compiling" = yes; then :
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: maybe" >&5
-$as_echo "maybe" >&6; }
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING:
-*** Skipping thread test program because of cross-compile build.
-" >&5
-$as_echo "$as_me: WARNING:
-*** Skipping thread test program because of cross-compile build.
-" >&2;}
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include "$srcdir/config/thread_test.c"
-_ACEOF
-if ac_fn_c_try_run "$LINENO"; then :
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-$as_echo "yes" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-  as_fn_error $? "thread test program failed
-This platform is not thread-safe.  Check the file 'config.log' for the
-exact reason, or use --disable-thread-safety to disable thread safety." "$LINENO" 5
-fi
-rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
-  conftest.$ac_objext conftest.beam conftest.$ac_ext
-fi
-
-CFLAGS="$_CFLAGS"
-LIBS="$_LIBS"
-else
-{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: *** skipping thread test on Win32" >&5
-$as_echo "$as_me: WARNING: *** skipping thread test on Win32" >&2;}
-fi
-fi
-
 # If compiler will take -Wl,--as-needed (or various platform-specific
 # spellings thereof) then add that to LDFLAGS.  This is much easier than
 # trying to filter LIBS to the minimum for each executable.

configure.ac

@@ -1173,17 +1173,13 @@ AC_SEARCH_LIBS(shm_unlink, rt)
 AC_SEARCH_LIBS(clock_gettime, [rt posix4])
 # Solaris:
 AC_SEARCH_LIBS(fdatasync, [rt posix4])
-# Required for thread_test.c on Solaris
-AC_SEARCH_LIBS(sched_yield, rt)
-# Required for thread_test.c on Solaris 2.5:
-# Other ports use it too (HP-UX) so test unconditionally
-AC_SEARCH_LIBS(gethostbyname_r, nsl)
 # Cygwin:
 AC_SEARCH_LIBS(shmget, cygipc)
 # *BSD:
 AC_SEARCH_LIBS(backtrace_symbols, execinfo)
 
 if test "$enable_thread_safety" = yes; then
+  AC_SEARCH_LIBS(gethostbyname_r, nsl)
   AC_SEARCH_LIBS(pthread_barrier_wait, pthread)
 fi
 
@@ -2330,38 +2326,6 @@ if test "$enable_tap_tests" = yes; then
   fi
 fi
 
-# Thread testing
-
-# We have to run the thread test near the end so we have all our symbols
-# defined.  Cross compiling throws a warning.
-#
-if test "$enable_thread_safety" = yes; then
-if test "$PORTNAME" != "win32"
-then
-AC_MSG_CHECKING([thread safety of required library functions])
-
-_CFLAGS="$CFLAGS"
-_LIBS="$LIBS"
-CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
-LIBS="$LIBS $PTHREAD_LIBS"
-AC_RUN_IFELSE(
-  [AC_LANG_SOURCE([[#include "$srcdir/config/thread_test.c"]])],
-  [AC_MSG_RESULT(yes)],
-  [AC_MSG_RESULT(no)
-  AC_MSG_ERROR([thread test program failed
-This platform is not thread-safe.  Check the file 'config.log' for the
-exact reason, or use --disable-thread-safety to disable thread safety.])],
-  [AC_MSG_RESULT(maybe)
-  AC_MSG_WARN([
-*** Skipping thread test program because of cross-compile build.
-])])
-CFLAGS="$_CFLAGS"
-LIBS="$_LIBS"
-else
-AC_MSG_WARN([*** skipping thread test on Win32])
-fi
-fi
-
 # If compiler will take -Wl,--as-needed (or various platform-specific
 # spellings thereof) then add that to LDFLAGS.  This is much easier than
 # trying to filter LIBS to the minimum for each executable.