Handle NULL for short descriptions of custom GUC variables

michaelpq · michaelpq · commit 1b40ceea24e6 · 2022-05-28T12:13:02.000+09:00
If a short description is specified as NULL in one of the various DefineCustomXXXVariable() functions available to external modules to define a custom parameter, SHOW ALL would crash. This change teaches SHOW ALL to properly handle NULL short descriptions, as well as any code paths that manipulate it, to gain in flexibility. Note that help_config.c was already able to do that, when describing a set of GUCs for postgres --describe-config. Author: Steve Chavez Reviewed by: Nathan Bossart, Andres Freund, Michael Paquier, Tom Lane Discussion: https://postgr.es/m/CAGRrpzY6hO-Kmykna_XvsTv8P2DshGiU6G3j8yGao4mk0CqjHA%40mail.gmail.com Backpatch-through: 10
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
@@ -8079,7 +8079,16 @@ ShowAllGUCConfig(DestReceiver *dest)
 			isnull[1] = true;
 		}
 
-		values[2] = PointerGetDatum(cstring_to_text(conf->short_desc));
+		if (conf->short_desc)
+		{
+			values[2] = PointerGetDatum(cstring_to_text(conf->short_desc));
+			isnull[2] = false;
+		}
+		else
+		{
+			values[2] = PointerGetDatum(NULL);
+			isnull[2] = true;
+		}
 
 		/* send it to dest */
 		do_tup_output(tstate, values, isnull);
@@ -8091,7 +8100,8 @@ ShowAllGUCConfig(DestReceiver *dest)
 			pfree(setting);
 			pfree(DatumGetPointer(values[1]));
 		}
-		pfree(DatumGetPointer(values[2]));
+		if (conf->short_desc)
+			pfree(DatumGetPointer(values[2]));
 	}
 
 	end_tup_output(tstate);
