Make "postgres -C guc" print "" not "(null)" for null-valued GUCs.

tglsfdc · tglsfdc · commit f2c28bb1f2fe · 2016-06-22T11:55:24.000-04:00
Commit 0b0baf2 et al made this case print "(null)" on the grounds that that's what happened on platforms that didn't crash. But neither behavior was actually intentional. What we should print is just an empty string, for compatibility with the behavior of SHOW and other ways of examining string GUCs. Those code paths don't distinguish NULL from empty strings, so we should not here either. Per gripe from Alain Radix. Like the previous patch, back-patch to 9.2 where -C option was introduced. Discussion: <CA+YdpwxPUADrmxSD7+Td=uOshMB1KkDN7G7cf+FGmNjjxMhjbw@mail.gmail.com>
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
@@ -828,7 +828,7 @@ PostmasterMain(int argc, char *argv[])
 		const char *config_val = GetConfigOption(output_config_variable,
 												 false, false);
 
-		puts(config_val ? config_val : "(null)");
+		puts(config_val ? config_val : "");
 		ExitPostmaster(0);
 	}
 

Original file line number	Diff line number	Diff line change
`@@ -828,7 +828,7 @@ PostmasterMain(int argc, char *argv[])`
`828`	`828`	`const char *config_val = GetConfigOption(output_config_variable,`
`829`	`829`	`false, false);`
`830`	`830`
`831`		`- puts(config_val ? config_val : "(null)");`
	`831`	`+ puts(config_val ? config_val : "");`
`832`	`832`	`ExitPostmaster(0);`
`833`	`833`	`}`
`834`	`834`