* module/system/il/compile.scm (codegen): Fix *another* bug in compiling
`or' -- in the case in which the value was being discarded, as in `or'
used as a control structure, we were sometimes leaving a value on the
stack.
* testsuite/t-or.scm: Add another test case for `or'.
* module/system/il/compile.scm (codegen): Rewrite handling of `and' and
`or' ghil compilation, because it was broken if drop was #t. Tricky
bug, this one! Took me days to track down!
* module/system/repl/repl.scm: Export call-with-backtrace, which probably
should go in some other file.
* src/vm.c (scm_vm_save_stack): Handle the fp==0 case for errors before
we have a frame.
* src/vm_engine.h (NEW_FRAME, FREE_FRAME): Stricter underflow checking,
raising the stack base to the return address, in an attempt to prevent
inadvertant stack smashing (the symptom of the and/or miscompilation
bug).
(CHECK_IP): A check that the current IP is within the bounds of the
current program. Not normally compiled in. Perhaps it should be?
* src/vm_system.c (halt): Set vp->ip to NULL. Paranoia, I know.
(return): Call CHECK_IP(), if such a thing is compiled in.
* testsuite/Makefile.am (vm_test_files):
* testsuite/t-catch.scm:
* testsuite/t-map.scm:
* testsuite/t-or.scm: New tests.
