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, 6 insertions, 0 deletions

diff --git a/struct.c b/struct.c
index a4e9eb8f..bd9644be 100644
--- a/struct.c
+++ b/struct.c
@@ -1123,6 +1123,12 @@ val static_slot_ensure(val stype, val sym, val newval, val no_error_p)
     uw_throwf(error_s, lit("~a: ~s isn't a valid slot name"),
               self, sym, nao);
 
+  if (trace_loaded) {
+    struct struct_type *st = stype_handle(&stype, self);
+    val name = list(meth_s, st->name, sym, nao);
+    trace_check(name);
+  }
+
   no_error_p = default_bool_arg(no_error_p);
   return static_slot_ens_rec(stype, sym, newval, no_error_p, self, 0);
 }