trace: implement redefinition checks.

The tracing module should warn when traced functions or
methods are being redefined, and stop tracing the original
methods.

* eval.c (trace_check): New function. Calls
sys:trace-redefined-check if the trace module has been
loaded, otherwise does nothing.
(op_defun, op_defmacro): Call trace_check to have a warning
issued for a redefined traced function or macro.

* eval.h (trace_check): Declared.

* lisplib.c (trace_loaded): New global variable.
(trace_instantiate): Flip trace_loaded to t.

* lisplib.h (trace_loaded): Declared.

* share/txr/stdlib/trace.tl (sys:trace-redefine-check): New
function. Checks two situations: traced function or method
is redefined (neither old nor new is traced any longer),
and traced method is overridden (base method continues to be
traced, override is not traced).

* struct.c (static_slot_ensure): Do a trace check here,
taking care of defmeth.

1 files changed, 1 insertions, 0 deletions

diff --git a/lisplib.h b/lisplib.h
index 57a98d6e..e54ec5c6 100644
--- a/lisplib.h
+++ b/lisplib.h
@@ -26,6 +26,7 @@
  */
 
 extern val dl_table;
+extern val trace_loaded;
 void lisplib_init(void);
 val lisplib_try_load(val sym);
 void set_dlt_entries(val dlt, val *name, val fun);