add Guido's reasoning behind running all tests twice

diff --git a/Makefile.pre.in b/Makefile.pre.in
index 207798eff4ee887c52f2350d882400ccfe37fe74..843c50fd4b08c8cea9065ea1b20096005b12b642 100644 (file)
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -514,6 +514,13 @@ $(LIBRARY_OBJS) $(MODOBJS) Modules/$(MAINOBJ): $(PYTHON_HEADERS)
 ######################################################################
 
 # Test the interpreter (twice, once without .pyc files, once with)
+# In the past, we've had problems where bugs in the marshalling or
+# elsewhere caused bytecode read from .pyc files to behave differently
+# than bytecode generated directly from a .py source file.  Sometimes
+# the bytecode read from a .pyc file had the bug, somtimes the directly
+# generated bytecode.  This is sometimes a very shy bug needing a lot of
+# sample data.
+
 TESTOPTS=      -l
 TESTPROG=      $(srcdir)/Lib/test/regrtest.py
 TESTPYTHON=    $(RUNSHARED) ./$(BUILDPYTHON) -E -tt