Fix type confusion in guc_var_compare()

anarazel · anarazel · commit 2cf9bda76cfd · 2024-07-15T09:26:03.000-07:00
Before this change guc_var_compare() cast the input arguments to const struct config_generic *. That's not quite right however, as the input on one side is often just a char * on one side. Instead just use char *, the first field in config_generic. This fixes a -Warray-bounds warning with some versions of gcc. While the warning is only known to be triggered for <= 15, the issue the warning points out seems real, so apply the fix everywhere. Author: Nazir Bilal Yavuz <byavuz81@gmail.com> Reported-by: Erik Rijkers <er@xs4all.nl> Suggested-by: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/a74a1a0d-0fd2-3649-5224-4f754e8f91aa%40xs4all.nl
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
@@ -5291,10 +5291,10 @@ find_option(const char *name, bool create_placeholders, int elevel)
 static int
 guc_var_compare(const void *a, const void *b)
 {
-	const struct config_generic *confa = *(struct config_generic *const *) a;
-	const struct config_generic *confb = *(struct config_generic *const *) b;
+	const char *namea = **(const char ** const *) a;
+	const char *nameb = **(const char ** const *) b;
 
-	return guc_name_compare(confa->name, confb->name);
+	return guc_name_compare(namea, nameb);
 }
 
 /*

Original file line number	Diff line number	Diff line change
`@@ -5291,10 +5291,10 @@ find_option(const char *name, bool create_placeholders, int elevel)`
`5291`	`5291`	`static int`
`5292`	`5292`	`guc_var_compare(const void a, const void b)`
`5293`	`5293`	`{`
`5294`		`- const struct config_generic confa = (struct config_generic const ) a;`
`5295`		`- const struct config_generic confb = (struct config_generic const ) b;`
	`5294`	`+ const char namea = (const char * const *) a;`
	`5295`	`+ const char nameb = (const char * const *) b;`
`5296`	`5296`
`5297`		`- return guc_name_compare(confa->name, confb->name);`
	`5297`	`+ return guc_name_compare(namea, nameb);`
`5298`	`5298`	`}`
`5299`	`5299`
`5300`	`5300`	`/*`