tests: stack-overflow: avoid false failure

* tests/stack-overflow: This test would fail to elicit a stack overflow
diagnostic on some OS X systems. Rewrite to iterate, gradually increasing
the size of the input regex, stopping when grep emits the desired diagnostic
or the size reaches a reasonable limit.

1 files changed, 16 insertions, 7 deletions

diff --git a/tests/stack-overflow b/tests/stack-overflow
index 2042ebc5..69220455 100755
--- a/tests/stack-overflow
+++ b/tests/stack-overflow
@@ -3,14 +3,23 @@
 
 . "${srcdir=.}/init.sh"; path_prepend_ ../src
 
-# Too many open parentheses.
-printf %080000d 0|tr 0 '(' > in || framework_failure_
 echo grep: stack overflow > exp || framework_failure_
 
+# grep attempts to detect overflow via gnulib's c-stack module.
+# Trigger that with an input regex composed solely of open parentheses,
+# increasing the size of that input until grep emits the expected diagnostic.
 fail=0
-returns_ 2 grep -E -f in >out 2>err || fail=1
+for i in 1 3 5 10 20 30 40 50 100 200; do
+  # Create a file containing $i * 10000 open parentheses:
+  printf %0${i}0000d 0|tr 0 '(' > in || framework_failure_
+  grep -E -f in >out 2>err; st=$?
+  if grep -q 'stack overflow' err; then
+    test $st = 2 || fail=1
+    compare /dev/null out || fail=1
+    compare exp err || fail=1
+    test $fail = 0 && Exit 0
+    fail_ 'printed "stack overflow", but something else was wrong'
+  fi
+done
 
-compare /dev/null out || fail=1
-compare exp err || fail=1
-
-Exit $fail
+fail_ 'grep never printed "stack overflow"'