mpbarrett: Found mpbarrett_reduce hanging on this testcase.

A Python program spun inside mpbarrett_reduce, attempting the
computation in this testcase.  The test program hung too, and debugging
it yielded the following information.  On entry, d and m were equal; for
some reason, in the MP_DEST call, d was being aliased to m again, even
though m was still active; of course, m/d now had refcount 1, and all
hell broke loose when m got dropped.

A ground-up rebuild made the problem go away, so maybe it was just fluff
in the build tree.  I'm leaving this test here anyway so that it'll
catch a return of the bug, and maybe I can investigate it more carefully
then.

diff --git a/tests/mpbarrett b/tests/mpbarrett
index 1438cb5..801b091 100644 (file)
--- a/tests/mpbarrett
+++ b/tests/mpbarrett
@@ -97,6 +97,16 @@ mpbarrett-exp {
   25906467774034212974484417859588980567136610347807401817990462701
   514778499400157641662814932021958856708417966520837469125919104431
   123456789012345678901234567890123456789012345678901234567890;
+
+  # --- Strange bug ---
+  #
+  # Strange memory corruption bug causing mpbarrett_reduce to hang.
+  # Seems to have vanished on a clean rebuild so maybe this was just build
+  # fluff or something.  Leave it here to pick up regression.
+
+  30916300184138066757562815127455898754391418637651479989257882011612153138316483396290143656363307389355307404813205623380378799585065876990874918745873480056891738964426752
+  2 44329
+  10975270953088118598390528358454369816072092233138947812823085741431681835772475760228604878294514156761050649439713085882651077696501584961485141097470430535290622475239424;
 }
 
 # --- Simultaneous exponentiation ---