Don't change verify_gens in tests.

tests/gc-cardmark.impure.lisp

@@ -8,10 +8,11 @@
 (with-test (:name :adjacent-barrier-elimination-sticky-marks
             :skipped-on (or :gc-stress
                             (:not :soft-card-marks)))
+  (let ((pre_verify_gen_0 (extern-alien "pre_verify_gen_0" int)))
    (setf (extern-alien "pre_verify_gen_0" int) 1)
    (loop repeat 1000000
          do (adjacent-barriers))
-  (setf (extern-alien "pre_verify_gen_0" int) 0))
+   (setf (extern-alien "pre_verify_gen_0" int) pre_verify_gen_0)))
 
 
 ;;; The layout of FOO must not get promoted from gen0 to gen1.

tests/gc-slow.impure.lisp

@@ -55,6 +55,7 @@
 #+sb-thread
 (with-test (:name :concurrently-alloc-code)
   ;; this debug setting may or may not find a problem, but it can't hurt to try
+  (let ((pre_verify_gen_0 (extern-alien "pre_verify_gen_0" int)))
    (setf (extern-alien "pre_verify_gen_0" int) 1)
    (let ((worker-th
            (sb-thread:make-thread
@@ -73,4 +74,4 @@
        (let ((compiles (sb-thread:join-thread worker-th)))
          (format t "~&Compiled ~D times, GC'ed ~D times~%"
                  compiles gcs))))
-  (setf (extern-alien "pre_verify_gen_0" int) 0))
+   (setf (extern-alien "pre_verify_gen_0" int) pre_verify_gen_0)))

tests/lockfree-list.pure.lisp

@@ -116,6 +116,7 @@
     (gc)
     (when show (show (list-head *lfl*) #'get-next "del "))))
 
+(defvar *old-verify-gens* (sb-alien:extern-alien "verify_gens" char))
 ;; Enable heap validity tester
 #+(and generational (not gc-stress)) (setf (sb-alien:extern-alien "verify_gens" char) 0)
 
@@ -526,3 +527,6 @@
                       (if (< i (1- nthreads)) (+ chunk-start chunk-size))))
         (incf chunk-start chunk-size))
       (tester lflist worklists))))
+
+#+(and generational (not gc-stress))
+(setf (sb-alien:extern-alien "verify_gens" char) *old-verify-gens*)