tests: fix stack overflow test case for old gmake.

* tests/012/stack.tl: The (if stack-limited ...) test is not
correct because even if gerlimit indicates an unlimited stack,
we impose a defualt limit, and so (get-stack-limit) returns a
an integer value. The idea here was to try to skip this test
case when the stack usage is unlmited, which happens under
older versions of GNU make, before posix_spawn was introduced.
Instead, let's execute this test case only if we have
setrlimit. In the forked child, we try to impose a small stack
limit that will give use the stack overflow crash we are
testing for. The objective of the test case is to validate
that when (set-stack-limit 0) is called, the child will abort
due to a signal, rather than (recur) returning :so.

1 files changed, 7 insertions, 2 deletions

diff --git a/tests/012/stack.tl b/tests/012/stack.tl
index 62df252b..b3cea078 100644
--- a/tests/012/stack.tl
+++ b/tests/012/stack.tl
@@ -10,10 +10,15 @@
 
 (test (so (recur)) :so)
 
-(if stack-limited
+(if (fboundp 'setrlimit)
   (test (let ((pid (fork)))
           (cond
-            ((zerop pid) (set-stack-limit 0) (recur))
+            ((zerop pid)
+             (set-stack-limit 0)
+             (let ((rlim (getrlimit rlimit-stack)))
+               (set rlim.cur 32768)
+               (setrlimit rlimit-stack rlim))
+             (recur))
             (t (let ((status (wait pid)))
                  (w-ifsignaled status)))))
         t))