Index: lib/nfcomp.lisp
===================================================================
--- lib/nfcomp.lisp	(revision 14310)
+++ lib/nfcomp.lisp	(working copy)
@@ -198,8 +198,8 @@
               output-file (pathname-type
                            (backend-target-fasl-pathname
                             *target-backend*))))
-    (let* ((*features* (append (if (listp features) features (list features)) (setup-target-features target-backend *features*)))
-           (*fasl-deferred-warnings* nil) ; !!! WITH-COMPILATION-UNIT ...
+    
+    (let* ((*fasl-deferred-warnings* nil) ; !!! WITH-COMPILATION-UNIT ...
            (*fasl-save-local-symbols* save-local-symbols)
            (*save-source-locations* save-source-locations)
            (*fasl-save-doc-strings* save-doc-strings)
@@ -222,41 +222,54 @@
            (*fasl-compile-time-env* (new-lexical-environment (new-definition-environment)))
            (*fcomp-external-format* external-format)
            (forms nil))
-      (let ((current *outstanding-deferred-warnings*) last)
-        (when (and current
-                   (setq last (deferred-warnings.last-file current))
-                   (equalp *compile-file-pathname* (cdr last)))
-          ;; Discard previous deferred warnings when recompiling exactly the same file again,
-          ;; since most likely this is due to an interactive "retry compilation" request and
-          ;; we want to avoid duplicate warnings.
-          (setf (deferred-warnings.last-file current) nil)))
+      ;; This hair is to allow things to push stuff onto *features*.  What
+      ;; about thread-safety here?
+      (let ((old-features *features*)
+            (new-features (append (if (listp features) 
+                                    features 
+                                    (list features))
+                                  (setup-target-features target-backend *features*))))
+        (unwind-protect
+            (progn
+              (setf *features* new-features)
+              (let ((current *outstanding-deferred-warnings*) last)
+                (when (and current
+                           (setq last (deferred-warnings.last-file current))
+                           (equalp *compile-file-pathname* (cdr last)))
+                  ;; Discard previous deferred warnings when recompiling
+                  ;; exactly the same file again, since most likely this is
+                  ;; due to an interactive "retry compilation" request and
+                  ;; we want to avoid duplicate warnings.
+                  (setf (deferred-warnings.last-file current) nil)))
+              
+              (let* ((*outstanding-deferred-warnings* (%defer-warnings nil)))
+                (rplacd (defenv.type defenv) *outstanding-deferred-warnings*)
+                (setf (defenv.defined defenv) (deferred-warnings.defs *outstanding-deferred-warnings*))
+                
+                (setq forms (fcomp-file src
+                                        (or compile-file-original-truename (namestring orig-src))
+                                        compile-file-original-buffer-offset
+                                        lexenv))
+                
+                (setf (deferred-warnings.warnings *outstanding-deferred-warnings*) 
+                      (append *fasl-deferred-warnings* (deferred-warnings.warnings *outstanding-deferred-warnings*)))
+                (when *compile-verbose* (fresh-line))
+                (multiple-value-bind (any harsh) (report-deferred-warnings *compile-file-pathname*)
+                  (setq *fasl-warnings-signalled-p* (or *fasl-warnings-signalled-p* any)
+                        *fasl-non-style-warnings-signalled-p* (if (eq harsh :very) :very
+                                                                (or *fasl-non-style-warnings-signalled-p* harsh)))))
+              (when (and *fasl-break-on-program-errors* (eq *fasl-non-style-warnings-signalled-p* :very))
+                (cerror "create the output file despite the errors"
+                        "Serious errors encountered during compilation of ~s"
+                        src))
+              (fasl-scan-forms-and-dump-file forms output-file lexenv)
+              (values output-file
+                      (truename (pathname output-file)) 
+                      *fasl-warnings-signalled-p* 
+                      (and *fasl-non-style-warnings-signalled-p* t)))
+          (setf *features* (append (set-difference *features* new-features)
+                                   old-features)))))))
 
-      (let* ((*outstanding-deferred-warnings* (%defer-warnings nil)))
-        (rplacd (defenv.type defenv) *outstanding-deferred-warnings*)
-        (setf (defenv.defined defenv) (deferred-warnings.defs *outstanding-deferred-warnings*))
-
-        (setq forms (fcomp-file src
-                                (or compile-file-original-truename (namestring orig-src))
-                                compile-file-original-buffer-offset
-                                lexenv))
-
-        (setf (deferred-warnings.warnings *outstanding-deferred-warnings*) 
-              (append *fasl-deferred-warnings* (deferred-warnings.warnings *outstanding-deferred-warnings*)))
-        (when *compile-verbose* (fresh-line))
-        (multiple-value-bind (any harsh) (report-deferred-warnings *compile-file-pathname*)
-          (setq *fasl-warnings-signalled-p* (or *fasl-warnings-signalled-p* any)
-                *fasl-non-style-warnings-signalled-p* (if (eq harsh :very) :very
-                                                        (or *fasl-non-style-warnings-signalled-p* harsh)))))
-      (when (and *fasl-break-on-program-errors* (eq *fasl-non-style-warnings-signalled-p* :very))
-        (cerror "create the output file despite the errors"
-                "Serious errors encountered during compilation of ~s"
-                src))
-      (fasl-scan-forms-and-dump-file forms output-file lexenv)
-      (values output-file
-              (truename (pathname output-file)) 
-              *fasl-warnings-signalled-p* 
-              (and *fasl-non-style-warnings-signalled-p* t)))))
-
 (defvar *fcomp-locked-hash-tables*)
 (defvar *fcomp-load-forms-environment* nil)