From: Nathan Bossart <nathandbossart@gmail.com>
Date: Mon, 23 Jan 2023 09:49:22 -0800
Subject: [PATCH v10 1/4] introduce routine for checking mutually exclusive
 parameters

---
 src/backend/postmaster/pgarch.c |  7 ++-----
 src/backend/utils/misc/guc.c    | 14 ++++++++++++++
 src/include/utils/guc.h         |  2 ++
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index 8ecdb9ca23..8e91f2d70f 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -831,11 +831,8 @@ LoadArchiveLibrary(void)
 {
 	ArchiveModuleInit archive_init;
 
-	if (XLogArchiveLibrary[0] != '\0' && XLogArchiveCommand[0] != '\0')
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("both archive_command and archive_library set"),
-				 errdetail("Only one of archive_command, archive_library may be set.")));
+	CheckMutuallyExclusiveGUCs(XLogArchiveLibrary, "archive_library",
+							   XLogArchiveCommand, "archive_command");
 
 	memset(&ArchiveContext, 0, sizeof(ArchiveModuleCallbacks));
 
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index d52069f446..7858e9a649 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -6880,3 +6880,17 @@ call_enum_check_hook(struct config_enum *conf, int *newval, void **extra,
 
 	return true;
 }
+
+/*
+ * ERROR if both parameters are set.
+ */
+void
+CheckMutuallyExclusiveGUCs(const char *p1val, const char *p1name,
+						   const char *p2val, const char *p2name)
+{
+	if (p1val[0] != '\0' && p2val[0] != '\0')
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("both %s and %s set", p1name, p2name),
+				 errdetail("Only one of %s, %s may be set.", p1name, p2name)));
+}
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index ba89d013e6..947597247f 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -404,6 +404,8 @@ extern void *guc_malloc(int elevel, size_t size);
 extern pg_nodiscard void *guc_realloc(int elevel, void *old, size_t size);
 extern char *guc_strdup(int elevel, const char *src);
 extern void guc_free(void *ptr);
+extern void CheckMutuallyExclusiveGUCs(const char *p1val, const char *p1name,
+									   const char *p2val, const char *p2name);
 
 #ifdef EXEC_BACKEND
 extern void write_nondefault_variables(GucContext context);
-- 
2.25.1


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