process startup: Centralize pgwin32_signal_initialize() calls.

For one, the existing location lead to somewhat awkward code in main(). For
another, the new location is easier to understand anyway.

Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-By: Robert Haas <robertmhaas@gmail.com>
Discussion: https://postgr.es/m/20210802164124.ufo5buo4apl6yuvs@alap3.anarazel.de

src/backend/main/main.c

@@ -181,35 +181,24 @@ main(int argc, char *argv[])
 	 * Dispatch to one of various subprograms depending on first argument.
 	 */
 
-#ifdef EXEC_BACKEND
-	if (argc > 1 && strncmp(argv[1], "--fork", 6) == 0)
-		SubPostmasterMain(argc, argv);	/* does not return */
-#endif
-
-#ifdef WIN32
-
-	/*
-	 * Start our win32 signal implementation
-	 *
-	 * SubPostmasterMain() will do this for itself, but the remaining modes
-	 * need it here
-	 */
-	pgwin32_signal_initialize();
-#endif
-
 	if (argc > 1 && strcmp(argv[1], "--check") == 0)
 		BootstrapModeMain(argc, argv, true);
 	else if (argc > 1 && strcmp(argv[1], "--boot") == 0)
 		BootstrapModeMain(argc, argv, false);
+#ifdef EXEC_BACKEND
+	else if (argc > 1 && strncmp(argv[1], "--fork", 6) == 0)
+		SubPostmasterMain(argc, argv);
+#endif
 	else if (argc > 1 && strcmp(argv[1], "--describe-config") == 0)
-		GucInfoMain();			/* does not return */
+		GucInfoMain();
 	else if (argc > 1 && strcmp(argv[1], "--single") == 0)
 		PostgresMain(argc, argv,
 					 NULL,		/* no dbname */
-					 strdup(get_user_name_or_exit(progname)));	/* does not return */
+					 strdup(get_user_name_or_exit(progname)));
 	else
-		PostmasterMain(argc, argv); /* does not return */
+		PostmasterMain(argc, argv);
-	abort();					/* should not get here */
+	/* the functions above should not return */
+	abort();
 }
 
 

src/backend/postmaster/postmaster.c

@@ -4905,15 +4905,6 @@ SubPostmasterMain(int argc, char *argv[])
 	/* Close the postmaster's sockets (as soon as we know them) */
 	ClosePostmasterPorts(strcmp(argv[1], "--forklog") == 0);
 
-	/*
-	 * Start our win32 signal implementation. This has to be done after we
-	 * read the backend variables, because we need to pick up the signal pipe
-	 * from the parent process.
-	 */
-#ifdef WIN32
-	pgwin32_signal_initialize();
-#endif
-
 	/* Setup as postmaster child */
 	InitPostmasterChild();
 

src/backend/utils/init/miscinit.c

@@ -87,13 +87,23 @@ bool		IgnoreSystemIndexes = false;
 /*
  * Initialize the basic environment for a postmaster child
  *
- * Should be called as early as possible after the child's startup.
+ * Should be called as early as possible after the child's startup. However,
+ * on EXEC_BACKEND builds it does need to be after read_backend_variables().
  */
 void
 InitPostmasterChild(void)
 {
 	IsUnderPostmaster = true;	/* we are a postmaster subprocess now */
 
+	/*
+	 * Start our win32 signal implementation. This has to be done after we
+	 * read the backend variables, because we need to pick up the signal pipe
+	 * from the parent process.
+	 */
+#ifdef WIN32
+	pgwin32_signal_initialize();
+#endif
+
 	/*
 	 * Set reference point for stack-depth checking. We re-do that even in the
 	 * !EXEC_BACKEND case, because there are some edge cases where processes
@@ -166,6 +176,13 @@ InitStandaloneProcess(const char *argv0)
 {
 	Assert(!IsPostmasterEnvironment);
 
+	/*
+	 * Start our win32 signal implementation
+	 */
+#ifdef WIN32
+	pgwin32_signal_initialize();
+#endif
+
 	InitProcessGlobals();
 
 	/* Initialize process-local latch support */