https://cgit.freebsd.org/ports/tree/databases/libodbc++/files/patch-src-datetime.cpp
https://bugs.gentoo.org/855887

(Given the source, possibly fixes libcxx too?)
--- a/src/datetime.cpp
+++ b/src/datetime.cpp
@@ -272,7 +272,7 @@
 # endif
 #endif
       ,ODBCXX_STRING_CONST("%09d"),nanos_);
-      buf[9] = NULL;// Terminate string
+      buf[9] = '\0';// Terminate string
     ret+=ODBCXX_STRING(buf);
   }
   return ret;