From f6caa58074a6dd66c57f2e8a1ff36e9fbe6530b9 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Wed, 25 Jan 2023 15:54:35 +0900
Subject: [PATCH v11 2/3] introduce routine for checking mutually exclusive
 parameters

---
 src/include/utils/guc.h         |  2 ++
 src/backend/postmaster/pgarch.c |  7 ++-----
 src/backend/utils/misc/guc.c    | 18 ++++++++++++++++++
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index ba89d013e6..d7785785c2 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -372,6 +372,8 @@ extern int	NewGUCNestLevel(void);
 extern void AtEOXact_GUC(bool isCommit, int nestLevel);
 extern void BeginReportingGUCOptions(void);
 extern void ReportChangedGUCOptions(void);
+extern void CheckMutuallyExclusiveGUCs(const char *p1val, const char *p1name,
+									   const char *p2val, const char *p2name);
 extern void ParseLongOption(const char *string, char **name, char **value);
 extern const char *get_config_unit_name(int flags);
 extern bool parse_int(const char *value, int *result, int flags,
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..e63515d624 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2558,6 +2558,24 @@ ReportChangedGUCOptions(void)
 	}
 }
 
+/*
+ * Check if two GUCs are mutually set.  Works only when comparing two
+ * string GUCs.
+ *
+ * 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("cannot set both %s and %s", p1name, p2name),
+				 errdetail("Only one of %s or %s may be set.",
+						   p1name, p2name)));
+}
+
 /*
  * ReportGUCOption: if appropriate, transmit option value to frontend
  *
-- 
2.39.0