Modernize our code for looking up descriptive strings for Unix signals.

At least as far back as the 2008 spec, POSIX has defined strsignal(3)
for looking up descriptive strings for signal numbers.  We hadn't gotten
the word though, and were still using the crufty old sys_siglist array,
which is in no standard even though most Unixen provide it.

Aside from not being formally standards-compliant, this was just plain
ugly because it involved #ifdef's at every place using the code.

To eliminate the #ifdef's, create a portability function pg_strsignal,
which wraps strsignal(3) if available and otherwise falls back to
sys_siglist[] if available.  The set of Unixen with neither API is
probably empty these days, but on any platform with neither, you'll
just get "unrecognized signal".  All extant callers print the numeric
signal number too, so no need to work harder than that.

Along the way, upgrade pg_basebackup's child-error-exit reporting
to match the rest of the system.

Discussion: https://postgr.es/m/25758.1544983503@sss.pgh.pa.us

2 files changed, 6 insertions, 21 deletions

diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index f663d7befa..e88d545d65 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -650,17 +650,10 @@ 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
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index a33a131182..eedc617db4 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -3612,6 +3612,7 @@ 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,
 
@@ -3622,7 +3623,7 @@ 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,
 
 		/*------
@@ -3630,19 +3631,10 @@ 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,