Remove support for Unix systems without the POSIX signal APIs.

Remove configure's checks for HAVE_POSIX_SIGNALS, HAVE_SIGPROCMASK, and
HAVE_SIGSETJMP.  These APIs are required by the Single Unix Spec v2
(POSIX 1997), which we generally consider to define our minimum required
set of Unix APIs.  Moreover, no buildfarm member has reported not having
them since 2012 or before, which means that even if the code is still live
somewhere, it's untested --- and we've made plenty of signal-handling
changes of late.  So just take these APIs as given and save the cycles for
configure probes for them.

However, we can't remove as much C code as I'd hoped, because the Windows
port evidently still uses the non-POSIX code paths for signal masking.
Since we're largely emulating these BSD-style APIs for Windows anyway, it
might be a good thing to switch over to POSIX-like notation and thereby
remove a few more #ifdefs.  But I'm not in a position to code or test that.
In the meantime, we can at least make things a bit more transparent by
testing for WIN32 explicitly in these places.

11 files changed, 27 insertions, 200 deletions

diff --git a/config/c-library.m4 b/config/c-library.m4
index 7b1d9f4063d..1d28c454bae 100644
--- a/config/c-library.m4
+++ b/config/c-library.m4
@@ -170,33 +170,6 @@ AC_DEFUN([PGAC_STRUCT_ADDRINFO],
 ])])# PGAC_STRUCT_ADDRINFO
 
 
-# PGAC_FUNC_POSIX_SIGNALS
-# -----------------------
-# Check to see if the machine has the POSIX signal interface. Define
-# HAVE_POSIX_SIGNALS if so. Also set the output variable HAVE_POSIX_SIGNALS
-# to yes or no.
-#
-# Note that this test only compiles a test program, it doesn't check
-# whether the routines actually work. If that becomes a problem, make
-# a fancier check.
-AC_DEFUN([PGAC_FUNC_POSIX_SIGNALS],
-[AC_CACHE_CHECK(for POSIX signal interface, pgac_cv_func_posix_signals,
-[AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <signal.h>
-],
-[struct sigaction act, oact;
-sigemptyset(&act.sa_mask);
-act.sa_flags = SA_RESTART;
-sigaction(0, &act, &oact);])],
-[pgac_cv_func_posix_signals=yes],
-[pgac_cv_func_posix_signals=no])])
-if test x"$pgac_cv_func_posix_signals" = xyes ; then
-  AC_DEFINE(HAVE_POSIX_SIGNALS, 1,
-            [Define to 1 if you have the POSIX signal interface.])
-fi
-HAVE_POSIX_SIGNALS=$pgac_cv_func_posix_signals
-AC_SUBST(HAVE_POSIX_SIGNALS)])# PGAC_FUNC_POSIX_SIGNALS
-
-
 # PGAC_FUNC_SNPRINTF_LONG_LONG_INT_MODIFIER
 # ---------------------------------------
 # Determine which length modifier snprintf uses for long long int.  We
diff --git a/configure b/configure
index 0376a7ca919..99ef10f0f73 100755
--- a/configure
+++ b/configure
@@ -649,7 +649,6 @@ XGETTEXT
 MSGMERGE
 MSGFMT_FLAGS
 MSGFMT
-HAVE_POSIX_SIGNALS
 PG_CRC32C_OBJS
 CFLAGS_SSE42
 have_win32_dbghelp
@@ -12289,7 +12288,7 @@ fi
 LIBS_including_readline="$LIBS"
 LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
 
-for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat pthread_is_threaded_np readlink setproctitle setsid shm_open sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l
+for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat pthread_is_threaded_np readlink setproctitle setsid shm_open symlink sync_file_range towlower utime utimes wcstombs wcstombs_l
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
 ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
@@ -13048,38 +13047,6 @@ esac
 
 fi
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for sigsetjmp" >&5
-$as_echo_n "checking for sigsetjmp... " >&6; }
-if ${pgac_cv_func_sigsetjmp+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <setjmp.h>
-int
-main ()
-{
-sigjmp_buf x; sigsetjmp(x, 1);
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_link "$LINENO"; then :
-  pgac_cv_func_sigsetjmp=yes
-else
-  pgac_cv_func_sigsetjmp=no
-fi
-rm -f core conftest.err conftest.$ac_objext \
-    conftest$ac_exeext conftest.$ac_ext
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_func_sigsetjmp" >&5
-$as_echo "$pgac_cv_func_sigsetjmp" >&6; }
-if test x"$pgac_cv_func_sigsetjmp" = x"yes"; then
-
-$as_echo "#define HAVE_SIGSETJMP 1" >>confdefs.h
-
-fi
-
 ac_fn_c_check_decl "$LINENO" "sys_siglist" "ac_cv_have_decl_sys_siglist" "#include <signal.h>
 /* NetBSD declares sys_siglist in unistd.h.  */
 #ifdef HAVE_UNISTD_H
@@ -14635,54 +14602,6 @@ fi
 
 
 
-# Check that POSIX signals are available if thread safety is enabled.
-if test "$PORTNAME" != "win32"
-then
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for POSIX signal interface" >&5
-$as_echo_n "checking for POSIX signal interface... " >&6; }
-if ${pgac_cv_func_posix_signals+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <signal.h>
-
-int
-main ()
-{
-struct sigaction act, oact;
-sigemptyset(&act.sa_mask);
-act.sa_flags = SA_RESTART;
-sigaction(0, &act, &oact);
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_link "$LINENO"; then :
-  pgac_cv_func_posix_signals=yes
-else
-  pgac_cv_func_posix_signals=no
-fi
-rm -f core conftest.err conftest.$ac_objext \
-    conftest$ac_exeext conftest.$ac_ext
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_func_posix_signals" >&5
-$as_echo "$pgac_cv_func_posix_signals" >&6; }
-if test x"$pgac_cv_func_posix_signals" = xyes ; then
-
-$as_echo "#define HAVE_POSIX_SIGNALS 1" >>confdefs.h
-
-fi
-HAVE_POSIX_SIGNALS=$pgac_cv_func_posix_signals
-
-if test "$pgac_cv_func_posix_signals" != yes -a "$enable_thread_safety" = yes; then
-  as_fn_error $? "
-Thread-safety requires POSIX signals, which are not supported by this
-operating system;  use --disable-thread-safety to disable thread safety." "$LINENO" 5
-fi
-fi
-
-
 # Select semaphore implementation type.
 if test "$PORTNAME" != "win32"; then
   if test x"$USE_NAMED_POSIX_SEMAPHORES" = x"1" ; then
diff --git a/configure.in b/configure.in
index 5f16530fca8..4143451c40e 100644
--- a/configure.in
+++ b/configure.in
@@ -1406,7 +1406,7 @@ PGAC_FUNC_GETTIMEOFDAY_1ARG
 LIBS_including_readline="$LIBS"
 LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
 
-AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat pthread_is_threaded_np readlink setproctitle setsid shm_open sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l])
+AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat pthread_is_threaded_np readlink setproctitle setsid shm_open symlink sync_file_range towlower utime utimes wcstombs wcstombs_l])
 
 AC_REPLACE_FUNCS(fseeko)
 case $host_os in
@@ -1596,18 +1596,6 @@ if test "$PORTNAME" = "cygwin"; then
   AC_LIBOBJ(dirmod)
 fi
 
-dnl Cannot use AC_CHECK_FUNC because sigsetjmp may be a macro
-dnl (especially on GNU libc)
-dnl See also comments in c.h.
-AC_CACHE_CHECK([for sigsetjmp], pgac_cv_func_sigsetjmp,
-[AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <setjmp.h>],
-            [sigjmp_buf x; sigsetjmp(x, 1);])],
-            [pgac_cv_func_sigsetjmp=yes],
-            [pgac_cv_func_sigsetjmp=no])])
-if test x"$pgac_cv_func_sigsetjmp" = x"yes"; then
-  AC_DEFINE(HAVE_SIGSETJMP, 1, [Define to 1 if you have sigsetjmp().])
-fi
-
 AC_CHECK_DECLS([sys_siglist], [], [],
 [#include <signal.h>
 /* NetBSD declares sys_siglist in unistd.h.  */
@@ -1932,18 +1920,6 @@ fi
 AC_SUBST(PG_CRC32C_OBJS)
 
 
-# Check that POSIX signals are available if thread safety is enabled.
-if test "$PORTNAME" != "win32"
-then
-PGAC_FUNC_POSIX_SIGNALS
-if test "$pgac_cv_func_posix_signals" != yes -a "$enable_thread_safety" = yes; then
-  AC_MSG_ERROR([
-Thread-safety requires POSIX signals, which are not supported by this
-operating system;  use --disable-thread-safety to disable thread safety.])
-fi
-fi
-
-
 # Select semaphore implementation type.
 if test "$PORTNAME" != "win32"; then
   if test x"$USE_NAMED_POSIX_SEMAPHORES" = x"1" ; then
diff --git a/src/Makefile.global.in b/src/Makefile.global.in
index 39a7879bb69..6871c3c6143 100644
--- a/src/Makefile.global.in
+++ b/src/Makefile.global.in
@@ -432,9 +432,6 @@ host_cpu = @host_cpu@
 # Make HAVE_IPV6 available for initdb script creation
 HAVE_IPV6= @HAVE_IPV6@
 
-# The HP-UX port makefile, for one, needs access to this symbol
-HAVE_POSIX_SIGNALS= @HAVE_POSIX_SIGNALS@
-
 # This is mainly for use on FreeBSD, where we have both a.out and elf
 # systems now.  May be applicable to other systems to?
 ELF_SYSTEM= @ELF_SYS@
diff --git a/src/backend/libpq/pqsignal.c b/src/backend/libpq/pqsignal.c
index 5f17d765816..b19c4539f3f 100644
--- a/src/backend/libpq/pqsignal.c
+++ b/src/backend/libpq/pqsignal.c
@@ -18,7 +18,7 @@
 #include "libpq/pqsignal.h"
 
 
-#ifdef HAVE_SIGPROCMASK
+#ifndef WIN32
 sigset_t	UnBlockSig,
 			BlockSig,
 			StartupBlockSig;
@@ -45,7 +45,7 @@ int			UnBlockSig,
 void
 pqinitmask(void)
 {
-#ifdef HAVE_SIGPROCMASK
+#ifndef WIN32
 
 	sigemptyset(&UnBlockSig);
 
@@ -101,7 +101,7 @@ pqinitmask(void)
 #ifdef SIGALRM
 	sigdelset(&StartupBlockSig, SIGALRM);
 #endif
-#else
+#else							/* WIN32 */
 	/* Set the signals we want. */
 	UnBlockSig = 0;
 	BlockSig = sigmask(SIGQUIT) |
diff --git a/src/include/c.h b/src/include/c.h
index f5da4676c6f..8163b000df1 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -1051,9 +1051,9 @@ extern int	vsnprintf(char *str, size_t count, const char *fmt, va_list args);
 /*
  * When there is no sigsetjmp, its functionality is provided by plain
  * setjmp. Incidentally, nothing provides setjmp's functionality in
- * that case.
+ * that case.  We now support the case only on Windows.
  */
-#ifndef HAVE_SIGSETJMP
+#ifdef WIN32
 #define sigjmp_buf jmp_buf
 #define sigsetjmp(x,y) setjmp(x)
 #define siglongjmp longjmp
diff --git a/src/include/libpq/pqsignal.h b/src/include/libpq/pqsignal.h
index 4b85342f325..33642475314 100644
--- a/src/include/libpq/pqsignal.h
+++ b/src/include/libpq/pqsignal.h
@@ -15,27 +15,27 @@
 
 #include <signal.h>
 
-#ifdef HAVE_SIGPROCMASK
+#ifndef WIN32
 extern sigset_t UnBlockSig,
 			BlockSig,
 			StartupBlockSig;
 
 #define PG_SETMASK(mask)	sigprocmask(SIG_SETMASK, mask, NULL)
-#else							/* not HAVE_SIGPROCMASK */
+#else							/* WIN32 */
+/*
+ * Windows doesn't provide the POSIX signal API, so we use something
+ * approximating the old BSD signal API.
+ */
 extern int	UnBlockSig,
 			BlockSig,
 			StartupBlockSig;
 
-#ifndef WIN32
-#define PG_SETMASK(mask)	sigsetmask(*((int*)(mask)))
-#else
-#define PG_SETMASK(mask)		pqsigsetmask(*((int*)(mask)))
-int			pqsigsetmask(int mask);
-#endif
+extern int	pqsigsetmask(int mask);
 
+#define PG_SETMASK(mask)		pqsigsetmask(*(mask))
 #define sigaddset(set, signum)	(*(set) |= (sigmask(signum)))
 #define sigdelset(set, signum)	(*(set) &= ~(sigmask(signum)))
-#endif   /* not HAVE_SIGPROCMASK */
+#endif   /* WIN32 */
 
 extern void pqinitmask(void);
 
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 1dcc9a9ee7a..dda73a8b4ce 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -379,9 +379,6 @@
 /* Define to 1 if you have the `posix_fadvise' function. */
 #undef HAVE_POSIX_FADVISE
 
-/* Define to 1 if you have the POSIX signal interface. */
-#undef HAVE_POSIX_SIGNALS
-
 /* Define to 1 if the assembler supports PPC's LWARX mutex hint bit. */
 #undef HAVE_PPC_LWARX_MUTEX_HINT
 
@@ -443,12 +440,6 @@
 /* Define to 1 if you have the `shm_open' function. */
 #undef HAVE_SHM_OPEN
 
-/* Define to 1 if you have the `sigprocmask' function. */
-#undef HAVE_SIGPROCMASK
-
-/* Define to 1 if you have sigsetjmp(). */
-#undef HAVE_SIGSETJMP
-
 /* Define to 1 if you have the `snprintf' function. */
 #undef HAVE_SNPRINTF
 
diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32
index bf69ef5bdeb..6f7a773c5be 100644
--- a/src/include/pg_config.h.win32
+++ b/src/include/pg_config.h.win32
@@ -264,9 +264,6 @@
 /* Define to 1 if you have the <poll.h> header file. */
 /* #undef HAVE_POLL_H */
 
-/* Define to 1 if you have the POSIX signal interface. */
-/* #undef HAVE_POSIX_SIGNALS */
-
 /* Define to 1 if you have the `pstat' function. */
 /* #undef HAVE_PSTAT */
 
@@ -316,12 +313,6 @@
 /* Define to 1 if you have the `setsid' function. */
 /* #undef HAVE_SETSID */
 
-/* Define to 1 if you have the `sigprocmask' function. */
-/* #undef HAVE_SIGPROCMASK */
-
-/* Define to 1 if you have sigsetjmp(). */
-/* #undef HAVE_SIGSETJMP */
-
 /* Define to 1 if you have the `snprintf' function. */
 /* #undef HAVE_SNPRINTF */
 
diff --git a/src/makefiles/Makefile.hpux b/src/makefiles/Makefile.hpux
index 1917d61b436..97bd0ba6d9e 100644
--- a/src/makefiles/Makefile.hpux
+++ b/src/makefiles/Makefile.hpux
@@ -1,10 +1,3 @@
-# If we don't have POSIX signals, we need to use the libBSD signal routines.
-# (HPUX 9 and early HPUX 10 releases don't have POSIX signals.)  Link in
-# libBSD only in that case.
-ifeq ($(HAVE_POSIX_SIGNALS), no)
-   LIBS := -lBSD $(LIBS)
-endif
-
 # Using X/Open Networking Interfaces requires to link with libxnet.
 # Without specifying this, bind(), getpeername() and so on don't work
 # correctly in the LP64 data model.
diff --git a/src/port/pqsignal.c b/src/port/pqsignal.c
index f475b58acd0..3e538d8c985 100644
--- a/src/port/pqsignal.c
+++ b/src/port/pqsignal.c
@@ -11,30 +11,17 @@
  * IDENTIFICATION
  *	  src/port/pqsignal.c
  *
- *	A NOTE ABOUT SIGNAL HANDLING ACROSS THE VARIOUS PLATFORMS.
- *
- *	pg_config.h defines the macro HAVE_POSIX_SIGNALS for some platforms and
- *	not for others.  We use that here to decide how to handle signalling.
- *
- *	Ultrix and SunOS provide BSD signal(2) semantics by default.
- *
- *	SVID2 and POSIX signal(2) semantics differ from BSD signal(2)
- *	semantics.  We can use the POSIX sigaction(2) on systems that
- *	allow us to request restartable signals (SA_RESTART).
- *
- *	Some systems don't allow restartable signals at all unless we
- *	link to a special BSD library.
- *
- *	We devoutly hope that there aren't any Unix-oid systems that provide
- *	neither POSIX signals nor BSD signals.  The alternative is to do
- *	signal-handler reinstallation, which doesn't work well at all.
+ *	We now assume that all Unix-oid systems have POSIX sigaction(2)
+ *	with support for restartable signals (SA_RESTART).  We used to also
+ *	support BSD-style signal(2), but there really shouldn't be anything
+ *	out there anymore that doesn't have the POSIX API.
  *
  *	Windows, of course, is resolutely in a class by itself.  In the backend,
  *	we don't use this file at all; src/backend/port/win32/signal.c provides
  *	pqsignal() for the backend environment.  Frontend programs can use
- *	this version of pqsignal() if they wish, but beware that Windows
- *	requires signal-handler reinstallation, because indeed it provides
- *	neither POSIX signals nor BSD signals :-(
+ *	this version of pqsignal() if they wish, but beware that this does
+ *	not provide restartable signals on Windows.
+ *
  * ------------------------------------------------------------------------
  */
 
@@ -52,9 +39,7 @@
 pqsigfunc
 pqsignal(int signo, pqsigfunc func)
 {
-#if !defined(HAVE_POSIX_SIGNALS)
-	return signal(signo, func);
-#else
+#ifndef WIN32
 	struct sigaction act,
 				oact;
 
@@ -68,7 +53,9 @@ pqsignal(int signo, pqsigfunc func)
 	if (sigaction(signo, &act, &oact) < 0)
 		return SIG_ERR;
 	return oact.sa_handler;
-#endif   /* !HAVE_POSIX_SIGNALS */
+#else							/* WIN32 */
+	return signal(signo, func);
+#endif
 }
 
 #endif   /* !defined(WIN32) || defined(FRONTEND) */