Handle GUC memory right in older pgsql versions

http.c

@@ -314,25 +314,35 @@ http_strtolower(const char *input)
 
 
 #if PG_VERSION_NUM < 160000
+static void *
+guc_malloc(int elevel, size_t size)
+{
+	void	   *data;
+
+	/* Avoid unportable behavior of malloc(0) */
+	if (size == 0)
+		size = 1;
+	data = malloc(size);
+	if (data == NULL)
+		ereport(elevel,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory")));
+	return data;
+}
+
 static char *
 guc_strdup(int elevel, const char *src)
 {
-    char       *data;
-    MemoryContext oldcontext = MemoryContextSwitchTo(CacheMemoryContext);
-    data = pstrdup(src);
-    MemoryContextSwitchTo(oldcontext);
-
-    if (data == NULL)
-        ereport(elevel,
-                (errcode(ERRCODE_OUT_OF_MEMORY),
-                 errmsg("out of memory")));
-    return data;
+	size_t len = strlen(src) + 1;
+	char *dup = guc_malloc(elevel, len);
+	memcpy(dup, src, len);
+	return dup;
 }
 
 static void
 guc_free(void *ptr)
 {
-	pfree(ptr);
+	free(ptr);
 }
 #endif