0.7.9.52:

[sbcl.git] / BUGS

diff --git a/BUGS b/BUGS
index c746255..c3ad6f9 100644 (file)
--- a/BUGS
+++ b/BUGS
@@ -522,6 +522,40 @@ WORKAROUND:
     internal error, failed AVER:
       "(COMMON-LISP:EQ (SB!C::TN-ENVIRONMENT SB!C:TN) SB!C::TN-ENV)"
 
+  This examples better illustrates the problem:
+
+  (defun tst ()
+    (declare (optimize (speed 2) (debug 3)))
+    (flet ((m1 ()
+             (bar (if (foo) 1 2))
+             (let ((x (foo)))
+               (bar x (list x)))))
+      (if (catch nil)
+          (m1)
+          (m1))))
+
+  (X is allocated in the physical environment of M1; X is :WRITE in
+  the call of LET [convert-to-global]; IF makes sure that a block
+  exists in M1 before this call.)
+
+  Because X is :DEBUG-ENVIRONMENT, it is :LIVE by default in all
+  blocks in the environment, particularly it is :LIVE in the start of
+  M1 (where it is not yet :WRITE) [setup-environment-tn-conflicts].
+
+  Then :LIVE is propagated backwards, i.e. into the caller of M1
+  where X does not exist [lifetime-flow-analysis].
+
+  (CATCH NIL) causes all TNs to be saved; Python fails on saving
+  non-existent variable; if it is replaced with (FOO), the problem
+  appears when debugging TST: LIST-LOCALS says
+
+    debugger invoked on condition of type SB-DI:UNKNOWN-DEBUG-VAR:
+
+    #<SB-DI::COMPILED-DEBUG-VAR X 0
+      {905FF7D}> is not in #<SB-DI::COMPILED-DEBUG-FUNCTION TST>.
+
+  (in those old versions, in which debugger worked :-().
+
 117:
   When the compiler inline expands functions, it may be that different
   kinds of return values are generated from different code branches.