Replace use of sys_siglist[] with strsignal().

This commit back-patches the v12-era commits a73d08319, cc92cca43,
and 7570df0f3 into supported pre-v12 branches.  The net effect is to
eliminate our former dependency on the never-standard sys_siglist[]
array, instead using POSIX-standard strsignal(3).

What motivates doing this now is that glibc just removed sys_siglist[]
from the set of symbols available to newly-built programs.  While our
code can survive without sys_siglist[], it then fails to print any
description of the signal that killed a child process, which is a
non-negligible loss of friendliness.  We can expect that people will
be wanting to build the back branches on platforms that include this
change, so we need to do something.

Since strsignal(3) has existed for quite a long time, and we've not
had any trouble with these patches so far in v12, it seems safe to
back-patch into older branches.

Discussion: https://postgr.es/m/3179114.1594853308@sss.pgh.pa.us

configure

@@ -12584,7 +12584,7 @@ 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 posix_fallocate pstat pthread_is_threaded_np readlink setproctitle setsid shm_open sigprocmask symlink sync_file_range towlower uselocale utime utimes wcstombs wcstombs_l
+for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll posix_fallocate pstat pthread_is_threaded_np readlink setproctitle setsid shm_open sigprocmask strsignal symlink sync_file_range towlower uselocale 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"
@@ -13476,25 +13476,6 @@ $as_echo "#define HAVE_SIGSETJMP 1" >>confdefs.h
 
 fi
 
-ac_fn_c_check_decl "$LINENO" "sys_siglist" "ac_cv_have_decl_sys_siglist" "#include <signal.h>
-/* NetBSD declares sys_siglist in unistd.h.  */
-#ifdef HAVE_UNISTD_H
-# include <unistd.h>
-#endif
-
-"
-if test "x$ac_cv_have_decl_sys_siglist" = xyes; then :
-  ac_have_decl=1
-else
-  ac_have_decl=0
-fi
-
-cat >>confdefs.h <<_ACEOF
-#define HAVE_DECL_SYS_SIGLIST $ac_have_decl
-_ACEOF
-
-
-
 ac_fn_c_check_func "$LINENO" "syslog" "ac_cv_func_syslog"
 if test "x$ac_cv_func_syslog" = xyes; then :
   ac_fn_c_check_header_mongrel "$LINENO" "syslog.h" "ac_cv_header_syslog_h" "$ac_includes_default"

configure.in

@@ -1483,6 +1483,7 @@ AC_CHECK_FUNCS(m4_normalize([
 	setsid
 	shm_open
 	sigprocmask
+	strsignal
 	symlink
 	sync_file_range
 	towlower
@@ -1695,8 +1696,6 @@ if test x"$pgac_cv_func_sigsetjmp" = x"yes"; then
   AC_DEFINE(HAVE_SIGSETJMP, 1, [Define to 1 if you have sigsetjmp().])
 fi
 
-AC_DECL_SYS_SIGLIST
-
 AC_CHECK_FUNC(syslog,
               [AC_CHECK_HEADER(syslog.h,
                                [AC_DEFINE(HAVE_SYSLOG, 1, [Define to 1 if you have the syslog interface.])])])

src/backend/postmaster/pgarch.c

@@ -598,17 +598,10 @@ pgarch_archiveXlog(char *xlog)
 				   errhint("See C include file \"ntstatus.h\" for a description of the hexadecimal value."),
 				   errdetail("The failed archive command was: %s",
 							 xlogarchcmd)));
-#elif defined(HAVE_DECL_SYS_SIGLIST) && HAVE_DECL_SYS_SIGLIST
-			ereport(lev,
-					(errmsg("archive command was terminated by signal %d: %s",
-							WTERMSIG(rc),
-			  WTERMSIG(rc) < NSIG ? sys_siglist[WTERMSIG(rc)] : "(unknown)"),
-					 errdetail("The failed archive command was: %s",
-							   xlogarchcmd)));
 #else
 			ereport(lev,
-					(errmsg("archive command was terminated by signal %d",
-							WTERMSIG(rc)),
+					(errmsg("archive command was terminated by signal %d: %s",
+							WTERMSIG(rc), pg_strsignal(WTERMSIG(rc))),
 					 errdetail("The failed archive command was: %s",
 							   xlogarchcmd)));
 #endif

src/backend/postmaster/postmaster.c

@@ -3528,6 +3528,7 @@ LogChildExit(int lev, const char *procname, int pid, int exitstatus)
 						procname, pid, WEXITSTATUS(exitstatus)),
 				 activity ? errdetail("Failed process was running: %s", activity) : 0));
 	else if (WIFSIGNALED(exitstatus))
+	{
 #if defined(WIN32)
 		ereport(lev,
 
@@ -3538,7 +3539,7 @@ LogChildExit(int lev, const char *procname, int pid, int exitstatus)
 						procname, pid, WTERMSIG(exitstatus)),
 				 errhint("See C include file \"ntstatus.h\" for a description of the hexadecimal value."),
 				 activity ? errdetail("Failed process was running: %s", activity) : 0));
-#elif defined(HAVE_DECL_SYS_SIGLIST) && HAVE_DECL_SYS_SIGLIST
+#else
 	ereport(lev,
 
 	/*------
@@ -3546,19 +3547,10 @@ LogChildExit(int lev, const char *procname, int pid, int exitstatus)
 	  "server process" */
 			(errmsg("%s (PID %d) was terminated by signal %d: %s",
 					procname, pid, WTERMSIG(exitstatus),
-					WTERMSIG(exitstatus) < NSIG ?
-					sys_siglist[WTERMSIG(exitstatus)] : "(unknown)"),
-	  activity ? errdetail("Failed process was running: %s", activity) : 0));
-#else
-		ereport(lev,
-
-		/*------
-		  translator: %s is a noun phrase describing a child process, such as
-		  "server process" */
-				(errmsg("%s (PID %d) was terminated by signal %d",
-						procname, pid, WTERMSIG(exitstatus)),
+						pg_strsignal(WTERMSIG(exitstatus))),
 				 activity ? errdetail("Failed process was running: %s", activity) : 0));
 #endif
+	}
 	else
 		ereport(lev,
 

src/bin/pg_basebackup/pg_basebackup.c

@@ -1848,7 +1848,7 @@ BaseBackup(void)
 	{
 #ifndef WIN32
 		int			status;
-		int			r;
+		pid_t		r;
 #else
 		DWORD		status;
 		/*
@@ -1875,7 +1875,7 @@ BaseBackup(void)
 
 		/* Just wait for the background process to exit */
 		r = waitpid(bgchild, &status, 0);
-		if (r == -1)
+		if (r == (pid_t) -1)
 		{
 			fprintf(stderr, _("%s: could not wait for child process: %s\n"),
 					progname, strerror(errno));
@@ -1884,19 +1884,13 @@ BaseBackup(void)
 		if (r != bgchild)
 		{
 			fprintf(stderr, _("%s: child %d died, expected %d\n"),
-					progname, r, (int) bgchild);
+					progname, (int) r, (int) bgchild);
 			disconnect_and_exit(1);
 		}
-		if (!WIFEXITED(status))
+		if (status != 0)
 		{
-			fprintf(stderr, _("%s: child process did not exit normally\n"),
-					progname);
-			disconnect_and_exit(1);
-		}
-		if (WEXITSTATUS(status) != 0)
-		{
-			fprintf(stderr, _("%s: child process exited with error %d\n"),
-					progname, WEXITSTATUS(status));
+			fprintf(stderr, "%s: %s\n",
+					progname, wait_result_to_str(status));
 			disconnect_and_exit(1);
 		}
 		/* Exited normally, we're happy! */

src/common/wait_error.c

@@ -58,25 +58,17 @@ wait_result_to_str(int exitstatus)
 		}
 	}
 	else if (WIFSIGNALED(exitstatus))
+	{
 #if defined(WIN32)
 		snprintf(str, sizeof(str),
 				 _("child process was terminated by exception 0x%X"),
 				 WTERMSIG(exitstatus));
-#elif defined(HAVE_DECL_SYS_SIGLIST) && HAVE_DECL_SYS_SIGLIST
-	{
-		char		str2[256];
-
-		snprintf(str2, sizeof(str2), "%d: %s", WTERMSIG(exitstatus),
-				 WTERMSIG(exitstatus) < NSIG ?
-				 sys_siglist[WTERMSIG(exitstatus)] : "(unknown)");
-		snprintf(str, sizeof(str),
-				 _("child process was terminated by signal %s"), str2);
-	}
 #else
 		snprintf(str, sizeof(str),
-				 _("child process was terminated by signal %d"),
-				 WTERMSIG(exitstatus));
+				 _("child process was terminated by signal %d: %s"),
+				 WTERMSIG(exitstatus), pg_strsignal(WTERMSIG(exitstatus)));
 #endif
+	}
 	else
 		snprintf(str, sizeof(str),
 				 _("child process exited with unrecognized status %d"),

src/include/pg_config.h.in

@@ -152,10 +152,6 @@
    don't. */
 #undef HAVE_DECL_STRTOULL
 
-/* Define to 1 if you have the declaration of `sys_siglist', and to 0 if you
-   don't. */
-#undef HAVE_DECL_SYS_SIGLIST
-
 /* Define to 1 if you have the declaration of `vsnprintf', and to 0 if you
    don't. */
 #undef HAVE_DECL_VSNPRINTF
@@ -520,6 +516,9 @@
 /* Define to 1 if you have the `strlcpy' function. */
 #undef HAVE_STRLCPY
 
+/* Define to 1 if you have the `strsignal' function. */
+#undef HAVE_STRSIGNAL
+
 /* Define to 1 if you have the `strtoll' function. */
 #undef HAVE_STRTOLL
 

src/include/pg_config.h.win32

@@ -373,6 +373,9 @@
 /* Define to 1 if you have the <string.h> header file. */
 #define HAVE_STRING_H 1
 
+/* Define to 1 if you have the `strsignal' function. */
+/* #undef HAVE_STRSIGNAL */
+
 /* Define to 1 if you have the `strtoll' function. */
 #ifdef HAVE_LONG_LONG_INT_64
 #define HAVE_STRTOLL 1

src/include/port.h

@@ -201,6 +201,9 @@ extern char *pgwin32_setlocale(int category, const char *locale);
 #define setlocale(a,b) pgwin32_setlocale(a,b)
 #endif   /* WIN32 */
 
+/* Wrap strsignal(), or provide our own version if necessary */
+extern const char *pg_strsignal(int signum);
+
 /* Portable prompt handling */
 extern char *simple_prompt(const char *prompt, int maxlen, bool echo);
 

src/port/Makefile

@@ -32,7 +32,7 @@ LIBS += $(PTHREAD_LIBS)
 
 OBJS = $(LIBOBJS) $(PG_CRC32C_OBJS) chklocale.o erand48.o inet_net_ntop.o \
 	noblock.o path.o pgcheckdir.o pgmkdirp.o pgsleep.o \
-	pgstrcasecmp.o pqsignal.o \
+	pgstrcasecmp.o pgstrsignal.o pqsignal.o \
 	qsort.o qsort_arg.o quotes.o sprompt.o tar.o thread.o
 
 # foo_srv.o and foo.o are both built from foo.c, but only foo.o has -DFRONTEND

src/port/pgstrsignal.c

@@ -0,0 +1,64 @@
+/*-------------------------------------------------------------------------
+ *
+ * pgstrsignal.c
+ *	  Identify a Unix signal number
+ *
+ * On platforms compliant with modern POSIX, this just wraps strsignal(3).
+ * Elsewhere, we do the best we can.
+ *
+ * This file is not currently built in MSVC builds, since it's useless
+ * on non-Unix platforms.
+ *
+ * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/port/pgstrsignal.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+
+/*
+ * pg_strsignal
+ *
+ * Return a string identifying the given Unix signal number.
+ *
+ * The result is declared "const char *" because callers should not
+ * modify the string.  Note, however, that POSIX does not promise that
+ * the string will remain valid across later calls to strsignal().
+ *
+ * This version guarantees to return a non-NULL pointer, although
+ * some platforms' versions of strsignal() reputedly do not.
+ *
+ * Note that the fallback cases just return constant strings such as
+ * "unrecognized signal".  Project style is for callers to print the
+ * numeric signal value along with the result of this function, so
+ * there's no need to work harder than that.
+ */
+const char *
+pg_strsignal(int signum)
+{
+	const char *result;
+
+	/*
+	 * If we have strsignal(3), use that --- but check its result for NULL.
+	 */
+#ifdef HAVE_STRSIGNAL
+	result = strsignal(signum);
+	if (result == NULL)
+		result = "unrecognized signal";
+#else
+
+	/*
+	 * We used to have code here to try to use sys_siglist[] if available.
+	 * However, it seems that all platforms with sys_siglist[] have also had
+	 * strsignal() for many years now, so that was just a waste of code.
+	 */
+	result = "(signal names not available on this platform)";
+#endif
+
+	return result;
+}

src/test/regress/pg_regress.c

@@ -1534,14 +1534,9 @@ log_child_failure(int exitstatus)
 #if defined(WIN32)
 		status(_(" (test process was terminated by exception 0x%X)"),
 			   WTERMSIG(exitstatus));
-#elif defined(HAVE_DECL_SYS_SIGLIST) && HAVE_DECL_SYS_SIGLIST
-		status(_(" (test process was terminated by signal %d: %s)"),
-			   WTERMSIG(exitstatus),
-			   WTERMSIG(exitstatus) < NSIG ?
-			   sys_siglist[WTERMSIG(exitstatus)] : "(unknown))");
 #else
-		status(_(" (test process was terminated by signal %d)"),
-			   WTERMSIG(exitstatus));
+		status(_(" (test process was terminated by signal %d: %s)"),
+			   WTERMSIG(exitstatus), pg_strsignal(WTERMSIG(exitstatus)));
 #endif
 	}
 	else