diff --git a/extra/mariabackup/backup_copy.cc b/extra/mariabackup/backup_copy.cc
index 161486fbe39..176d607fe1c 100644
--- a/extra/mariabackup/backup_copy.cc
+++ b/extra/mariabackup/backup_copy.cc
@@ -1009,7 +1009,6 @@ static int fix_win_file_permissions(const char *file)
 	ACL* pOldDACL;
 	SECURITY_DESCRIPTOR* pSD = NULL;
 	EXPLICIT_ACCESS ea = { 0 };
-	BOOL isWellKnownSID = FALSE;
 	PSID pSid = NULL;
 
 	GetSecurityInfo(hFile, SE_FILE_OBJECT, DACL_SECURITY_INFORMATION, NULL, NULL,
@@ -1029,7 +1028,7 @@ static int fix_win_file_permissions(const char *file)
 	ea.grfInheritance = CONTAINER_INHERIT_ACE | OBJECT_INHERIT_ACE;
 	ea.Trustee.TrusteeType = TRUSTEE_IS_UNKNOWN;
 	ACL* pNewDACL = 0;
-	DWORD err = SetEntriesInAcl(1, &ea, pOldDACL, &pNewDACL);
+	SetEntriesInAcl(1, &ea, pOldDACL, &pNewDACL);
 	if (pNewDACL)
 	{
 		SetSecurityInfo(hFile, SE_FILE_OBJECT, DACL_SECURITY_INFORMATION, NULL, NULL,
diff --git a/sql/mysql_install_db.cc b/sql/mysql_install_db.cc
index 85507a0abde..54bd46240bc 100644
--- a/sql/mysql_install_db.cc
+++ b/sql/mysql_install_db.cc
@@ -188,7 +188,7 @@ int main(int argc, char **argv)
       die("--datadir option not provided, and default datadir not found");
       my_print_help(my_long_options);
     }
-    strncat(default_datadir, "\\data", sizeof(default_datadir));
+    strcat_s(default_datadir, "\\data");
     opt_datadir= default_datadir;
     printf("Default data directory is %s\n",opt_datadir);
   }
diff --git a/sql/mysql_upgrade_service.cc b/sql/mysql_upgrade_service.cc
index 6a15364c849..05e2e970e6c 100644
--- a/sql/mysql_upgrade_service.cc
+++ b/sql/mysql_upgrade_service.cc
@@ -513,7 +513,7 @@ int main(int argc, char **argv)
       die("Cannot start mysqld.exe process, last error =%u", GetLastError());
     }
     char pipe_name[64];
-    snprintf(pipe_name, sizeof(pipe_name), "\\\\.\\pipe\\mysql_upgrade_service_%u",
+    snprintf(pipe_name, sizeof(pipe_name), "\\\\.\\pipe\\mysql_upgrade_service_%lu",
       GetCurrentProcessId());
     for (;;)
     {