* libguile/dynstack.h (SCM_DYNSTACK_TYPE_WITH_FLUID): Rename from
with-fluids.
* libguile/dynstack.c (scm_dynstack_push_fluid):
(scm_dynstack_unwind_fluid): Change API to only wind/unwind one
fluid binding.
(WITH_FLUID_WORDS): New define, always 2 words (fluid and value box).
(WITH_FLUID_FLUID, WITH_FLUID_VALUE_BOX): New macros to get offsets of
fluid and value box.
(scm_dynstack_push_rewinder, scm_dynstack_push_unwinder): Use
WINDER_WORDS.
(scm_dynstack_push_dynwind): Use DYNWIND_WORDS.
(scm_dynstack_wind_1): Update for scm_swap_fluid API change.
* libguile/fluids.h:
* libguile/fluids.c (scm_prepare_fluids): Remove; no longer needed.
(scm_swap_fluid): Update to just swap one fluid binding.
(scm_c_with_fluids, scm_c_with_fluid): Update to use
scm_dynstack_push_fluid.
* libguile/memoize.c (do_push_fluid, do_pop_fluid): Adapt to API
change.
* libguile/vm-engine.c (rtl_vm_engine): Change wind-fluids / unwind-fluids
to push-fluid / pop-fluid, and actually enable. Woo!
* libguile/vm-i-system.c (push-fluid, pop-fluid): Update to new API.
* libguile/vm-i-system.c (push-fluid, pop-fluid):
* doc/ref/vm.texi (Dynamic Environment Instructions): Rename wind-fluids
to push-fluid, and unwind-fluids to pop-fluid. They now only work on
one fluid binding at a time.
* module/ice-9/boot-9.scm (with-fluid*): Implement in Scheme in terms of
primcalls to push-fluid and pop-fluid.
(custom-throw-handler, catch, with-throw-handler): Use with-fluid*
instead of with-fluids, as with-fluids is no longer available before
psyntax is loaded.
(with-fluids): Define in Scheme in terms of with-fluid*.
* libguile/fluids.c (scm_with_fluid): Rename from scm_with_fluids, and
don't expose to Scheme.
* libguile/eval.c (eval): Remove SCM_M_WITH_FLUIDS case.
* libguile/expand.c (expand_with_fluids): Remove with-fluids syntax.
(DYNLET): Remove, no longer defining dynlet in the %expanded-vtables.
* libguile/expand.h: Remove dynlet definitions.
* module/ice-9/eval.scm (primitive-eval): Remove with-fluids case.
* libguile/memoize.c (do_push_fluid, do_pop_fluid): New primitive
helpers, like wind and unwind.
(memoize): Memoize wind and unwind primcalls. Don't memoize dynlet to
with-fluids.
(scm_init_memoize): Initialize push_fluid and pop_fluid here.
* libguile/memoize.h (SCM_M_WITH_FLUIDS): Remove definition.
* module/ice-9/psyntax.scm (build-dynlet): Remove; this just supported
with-fluids, which is now defined in boot-9.
* module/ice-9/psyntax-pp.scm: Regenerate.
* doc/ref/compiler.texi (Tree-IL):
* module/language/tree-il.scm:
* module/language/tree-il/analyze.scm:
* module/language/tree-il/canonicalize.scm:
* module/language/tree-il/compile-glil.scm:
* module/language/tree-il/cse.scm:
* module/language/tree-il/debug.scm:
* module/language/tree-il/effects.scm: Remove <dynlet>. Add cases for
primcalls to push-fluid and pop-fluid in compile-glil.scm and
effects.scm.
* module/language/tree-il/peval.scm (peval): Factor out
with-temporaries; probably a bad idea, but works for now. Factor out
make-begin0 (a better idea). Inline primcalls to with-fluid*, and
remove dynlet cases.
* module/language/tree-il/primitives.scm (*interesting-primitive-names*):
Add with-fluid*.
* libguile/vm.c (vm_error_kwargs_invalid_keyword,
vm_error_kwargs_unrecognized_keyword): Add parameter. Pass it
enclosed in a list as the last argument to `scm_error_scm'.
* libguile/vm-i-system.c (bind_kwargs): Adjust accordingly.
* libguile/eval.c (error_invalid_keyword, error_unrecognized_keyword):
Add parameter.
(prepare_boot_closure_env_for_apply): Adjust accordingly.
* module/ice-9/eval.scm (primitive-eval): Likewise.
* libguile/error.c (scm_error_scm): Mention `keyword-argument-error' in
docstring.
* module/ice-9/boot-9.scm (keyword-error-printer): New procedure; use it.
* test-suite/tests/optargs.test (c&e, with-test-prefix/c&e): Remove.
("define*")["unrecognized keyword"]: Test the value passed along the
`keyword-argument-error' exception.
["invalid keyword"]: New test.
* doc/ref/api-control.texi (Error Reporting): Update `scm-error'
description.
* libguile/vm-engine.c:
* libguile/vm-i-scheme.c:
* libguile/vm-i-system.c: CPP hygiene: the code that #defines, #undefs.
Makes things cleaner given the multiple inclusion dance we do.
* doc/ref/api-debug.texi (VM Hooks): Update documentation.
* libguile/vm.c (vm_dispatch_hook):
* libguile/vm-engine.c: Rework the hook machinery so that they can
receive an arbitrary number of arguments. The return and abort
hooks will pass the values that they return to their continuations.
(vm_engine): Adapt to ABORT_CONTINUATION_HOOK change.
* libguile/vm-i-system.c (return, return/values): Adapt to
POP_CONTINUATION_HOOK change.
* module/system/vm/frame.scm (frame-return-values): Remove. The
pop-continuation-hook will pass the values directly.
* module/system/vm/trace.scm (print-return):
(trace-calls-to-procedure):
(trace-calls-in-procedure): Update to receive return values
directly.
* module/system/vm/traps.scm (trap-in-procedure)
(trap-in-dynamic-extent): Ignore return values.
(trap-frame-finish, trap-calls-in-dynamic-extent)
(trap-calls-to-procedure): Pass return values to the handlers.
* doc/ref/api-procedures.texi (Case-lambda): Expand case-lambda*
documentation.
* module/ice-9/eval.scm (primitive-eval):
* libguile/eval.c (prepare_boot_closure_env_for_apply): Dispatch to the
next case-lambda clause if there are too many positionals.
* doc/ref/vm.texi (Function Prologue Instructions):
* libguile/vm-i-system.c (bind-optionals/shuffle-or-br): New
instruction, like bind-optionals/shuffle but can dispatch to the next
clause if there are too many positionals.
* module/language/assembly/disassemble.scm (code-annotation):
* module/language/assembly/decompile-bytecode.scm (decode-load-program):
* module/language/assembly/compile-bytecode.scm (compile-bytecode): Add
case for bind-optionals/shuffle-or-br.
* module/language/glil/compile-assembly.scm (glil->assembly): If there
is an alternate, use bind-optionals/shuffle-or-br instead of
bind-optionals/shuffle.
* test-suite/tests/optargs.test ("case-lambda*"): Add tests.
This commit removes code that was newly deprecated in stable-2.0.
Conflicts:
libguile/deprecated.c
libguile/deprecated.h
libguile/modules.c
module/ice-9/boot-9.scm
module/ice-9/deprecated.scm
* libguile/deprecated.h:
* libguile/deprecated.c (scm_sym2var): Deprecate this function.
* libguile/modules.h:
* libguile/modules.c (scm_module_ensure_local_variable): New public
function, replacing scm_sym2var with a true definep, without going
through eval closures (which are deprecated).
(scm_current_module): Rework to do something sensible before modules
are booted.
(scm_module_lookup, scm_lookup): Refactor to use scm_module_variable.
(scm_module_define, scm_define): Refactor to use
scm_module_ensure_local_variable.
* libguile/vm-i-system.c (define!): Use scm_define.
* libguile/vm.c (resolve_variable): Use scm_module_lookup.
* libguile/macros.c (scm_make_syntax_transformer): Use
scm_module_variable.
* libguile/gdbint.c (gdb_binding): Use scm_define.
* doc/ref/api-modules.texi (Accessing Modules from C): Add docs for
scm_module_ensure_local_variable.
* libguile/frames.c (scm_frame_instruction_pointer):
* module/system/vm/frame.scm (frame-bindings):
(frame-next-source, frame-call-representation): Fix a few locations
that thought that the frame-procedure will always be a VM
procedure. This will not not be the case when traversing the stack of
an application of a non-procedure.
* libguile/vm-i-system.c (call, tail-call, mv-call): Instead of
special-casing structs and smobs at these call sites, just set up the
stack, and jump to a generic apply loop if the proc is not a program.
* libguile/vm-engine.c: The generic apply loop is here. Also, the boot
program is now simply a boot continuation, and can handle any number
of arguments.
* libguile/vm.c (make_boot_program): Update the code that makes the boot
continuation.
* libguile/vm.c:
(vm_error):
(vm_error_bad_instruction):
(vm_error_unbound):
(vm_error_unbound_fluid):
(vm_error_not_a_variable):
(vm_error_not_a_thunk):
(vm_error_apply_to_non_list):
(vm_error_kwargs_length_not_even):
(vm_error_kwargs_invalid_keyword):
(vm_error_kwargs_unrecognized_keyword):
(vm_error_too_many_args):
(vm_error_wrong_num_args):
(vm_error_wrong_type_apply):
(vm_error_stack_overflow):
(vm_error_stack_underflow):
(vm_error_improper_list):
(vm_error_not_a_pair):
(vm_error_not_a_bytevector):
(vm_error_not_a_struct):
(vm_error_no_values):
(vm_error_not_enough_values):
(vm_error_continuation_not_rewindable):
(vm_error_bad_wide_string_length):
(vm_error_invalid_address):
(vm_error_object):
(vm_error_free_variable): New internal helpers, implementing VM error
handling.
* libguile/vm-engine.h (VM_ASSERT): New helper macro.
(ASSERT, CHECK_OBJECT, CHECK_FREE_VARIABLE):
(PRE_CHECK_UNDERFLOW, PUSH_LIST): Use the new helper.
* libguile/vm-i-loader.c:
* libguile/vm-i-scheme.c:
* libguile/vm-i-system.c: Use VM_ASSERT and the out-of-line error
handlers.
* libguile/vm-engine.c (vm_engine): Remove inline error handlers, and
remove a couple of local vars. Use VM_ASSERT. Have halt handle the
return itself.
* libguile/vm.c (prepare_smob_call): New helper. Now, instead of making
a per-smob trampoline, we will shuffle the smob into the args and use
a gsubr. This prevents a memory leak in which the trampolines, which
were values in a weak-key table, were preventing the smobs from being
collected.
* libguile/vm-i-system.c (call, tail-call, mv-call): Adapt to new smob
application mechanism.
(smob-call): Remove this instruction.
* libguile/smob.h (scm_smob_descriptor): Rename apply_trampoline_objcode
to apply_trampoline.
* libguile/smob.c: Remove our own objcode trampolines in favor of using
scm_c_make_gsubr.
(scm_smob_prehistory): No more trampoline weak map.
* libguile/procprop.c (scm_i_procedure_arity): Adapt to applicable smob
representation change.
* libguile/vm.c (prepare_smob_call): New helper. Now, instead of making
a per-smob trampoline, we will shuffle the smob into the args and use
a gsubr. This prevents a memory leak in which the trampolines, which
were values in a weak-key table, were preventing the smobs from being
collected.
* libguile/vm-i-system.c (call, tail-call, mv-call): Adapt to new smob
application mechanism.
(smob-call): Remove this instruction.
* libguile/smob.h (scm_smob_descriptor): Rename apply_trampoline_objcode
to apply_trampoline.
* libguile/smob.c: Remove our own objcode trampolines in favor of using
scm_c_make_gsubr.
(scm_smob_prehistory): No more trampoline weak map.
* libguile/procprop.c (scm_i_procedure_arity): Adapt to applicable smob
representation change.
* libguile/control.h: Remove scm_t_prompt_registers and
scm_c_make_prompt_registers.
(scm_c_abort): Take a pointer to a jmpbuf instead of a cookie. It
will serve the same purpose.
* libguile/control.c (reify_partial_continuation, scm_at_abort): Adapt
to new prompt representation.
* libguile/dynstack.h:
* libguile/dynstack.c (scm_dynstack_push_prompt): Prompts now have 5
words instead of 2, as they now push the fp, sp, ip, and jmpbuf on the
stack separately. This avoids allocation.
(scm_dynstack_find_prompt): Likewise, add return values for fp, sp,
etc.
(scm_dynstack_wind_prompt): Replaces scm_dynstack_relocate_prompt.
* libguile/eval.c (eval):
* libguile/stacks.c (find_prompt):
* libguile/throw.c (pre_init_catch): Adapt to the new prompt mechanism.
* libguile/vm-engine.c (vm_engine): Setjmp an on-stack jmpbuf every time
the VM enters. We can then re-use that jmpbuf for all prompts in that
invocation.
* libguile/vm-i-system.c (partial_cont_call): Adapt to change in prompt
representation. We don't need to wind here any more, since we pass in
the prompt's jmpbuf.
(prompt): Adapt to scm_dynstack_push_prompt change.
(abort): Adapt to vm_abort change.
* libguile/vm.h (struct scm_vm): No more cookie.
* libguile/vm.c (vm_abort): Adapt to scm_c_abort change.
(vm_reinstate_partial_continuation): Rewind the dynamic stack here,
now that we do have a valid jmpbuf.
(make_vm): No need to initialize a cookie.
* libguile/vm-i-system.c (wind):
* module/language/tree-il/compile-glil.scm (flatten-lambda-case):
Instead of making `wind' call `scm_thunk_p' on the winder and unwinder
at runtime, make it the responsibility of the compiler to emit code to
call thunk? and error, but only if the compiler cannot prove them to
be thunks.
* libguile/vm-engine.c (vm_engine): Remove a now-unused error block.
* libguile/dynstack.h:
* libguile/dynstack.c: New files, implementing the dynamic stack as a
true stack instead of a linked list. This lowers the cost of
dynwinds: frames, winders, prompts, with-fluids, and dynamic-wind.
For the most part, we allocate these items directly on the stack.
* libguile/dynwinds.h:
* libguile/dynwinds.c: Adapt all manipulators of the wind stack to use
interfaces from dynstack.c. Remove heap-allocated winder and frame
object types.
(scm_dowinds, scm_i_dowinds): Remove these. The first was exported,
but it was not a public interface.
* libguile/continuations.c:
* libguile/continuations.h (scm_t_contregs): Continuation objects
reference scm_t_dynstack* values now. Adapt to the new interfaces.
* libguile/control.c:
* libguile/control.h: There is no longer a scm_tc7_prompt kind of object
that can be allocated on the heap. Instead, the prompt flags, key,
and registers are pushed on the dynwind stack. (The registers are
still on the heap.) Also, since the vm_cont will reference the
dynwinds, make the partial continuation stub take just one extra arg,
instead of storing the intwinds separately in the object table.
* libguile/fluids.c:
* libguile/fluids.h: No more with-fluids objects; instead, the fluids go
on the dynstack. The values still have to be on the heap, though.
(scm_prepare_fluids, scm_swap_fluids): New internal functions,
replacing scm_i_make_with_fluids and scm_i_swap_with_fluids.
* libguile/print.c: Remove prompt and with-fluids printers.
* libguile/tags.h: Revert prompt and with-fluids tc7 values to what they
were before they were allocated.
* libguile/vm-i-system.c (partial_cont_call): Just pop the vmcont, the
intwinds will not be passed as a second arg. Rewind the dynamic stack
from within the VM, so that any rewinder sees valid prompt entries.
(call_cc, tail_call_cc): Adapt to pass the dynstack to
scm_i_vm_capture_stack.
(prompt, wind, unwind, wind_fluids, unwind_fluids): Adapt to the new
interfaces.
* libguile/vm.h (scm_i_capture_current_stack): Rename from
scm_i_vm_capture_continuation.
(scm_i_vm_capture_stack): Take a dynstack as an argument.
* libguile/vm.c (vm_reinstate_partial_continuation): Don't wind here, as
that could result in winders seeing invalid prompts.
* libguile/eval.c:
* libguile/root.c:
* libguile/stacks.c:
* libguile/threads.c:
* libguile/threads.h:
* libguile/throw.c: Adapt other users of dynwinds to use the dynstack.
* libguile/boolean.c (scm_nil_p): New function.
* libguile/vm-i-scheme.c (nilp, not_nilp):
* libguile/vm-i-system.c (br_if_nil, br_if_not_nil): New instructions.
Renumber other ops.
* libguile/_scm.h (SCM_OBJCODE_MINOR_VERSION): Increment.
* module/language/assembly/compile-bytecode.scm (compile-bytecode): Add
support for writing `br-if-nil' and `br-if-not-nil' instructions.
* module/language/assembly/disassemble.scm (code-annotation): Add
`br-if-nil' and `br-if-not-nil' to the list of branch instructions.
* module/language/tree-il/compile-glil.scm: Add `nil?' to
`*primcall-ops*'.
(flatten): Use the new branch instructions for `nil?' conditionals.
* module/language/tree-il/primitives.scm: Add `nil?' to
`*interesting-primitive-names*', `*effect-free-primitives', and
`*effect+exception-free-primitives*'.
* libguile/vm-engine.h (DEAD): New macro, nulls out a value.
* libguile/vm-i-system.c:
* libguile/vm-i-loader.c:
* libguile/vm-i-scheme.c: Use DEAD when variables become dead.
Later we can #ifdef this out, but I want to give the buildbots a try
with this patch to make sure it's correct.
Fixes part of <http://bugs.gnu.org/10520>.
Reported by Bruno Haible <bruno@clisp.org>.
* libguile/vm-i-system.c (COMPILER_BARRIER): New macro.
(halt, return, return_values): Insert compiler barrier after each
assignment to `fp'.
* libguile/fluids.c (grow_dynamic_state, new_fluid): Arrange for the
default value in the dynamic-state vector to be SCM_UNDEFINED instead
of SCM_BOOL_F. If the value in the dynamic-state is #f, default to a
value attached to the fluid instead. This allows useful default
values.
(scm_make_fluid_with_default): New function, allows the user to
specify a default value for the fluid. Defaults to #f. Bound to
`make-fluid' on the Scheme side.
(scm_make_unbound_fluid): Use SCM_UNDEFINED as the default in all
threads.
(scm_fluid_unset_x): Also unset the default value. Not sure if this
is the right thing.
(fluid_ref): Update to the new default-value strategy.
* libguile/threads.c (scm_i_reset_fluid): Reset to SCM_UNDEFINED.
* libguile/threads.h: Remove extra arg to scm_i_reset_fluid.
* libguile/vm-i-system.c (fluid-ref): Update to new default-value
strategy.
* module/ice-9/vlist.scm (block-growth-factor): Default to 2 in all
threads. Fixes http://debbugs.gnu.org/10093.
* libguile/__scm.h (SCM_ASYNC_TICK_WITH_CODE): Redefine to take a
scm_i_thread* as well. OK to do because it's within a
BUILDING_LIBGUILE block.
* libguile/vm-engine.c (vm_engine): Cache the scm_i_thread* instead of
the dynstate, so we can use the thread for ticks.
* libguile/vm-engine.h (VM_HANDLE_INTERRUPTS): Tick with the
scm_i_thread* local var, to avoid excessive tls calls.
* libguile/vm-i-system.c: Fix dynstate users to use
current_thread->dynamic_state.
* libguile/vm-engine.c (VM_CHECK_OBJECT, VM_CHECK_FREE_VARIABLES): Set
to 0 for both engines. These are really internal debugging variables,
which don't affect user-visible features, provided that the compiler
is correct of course.
(VM_CHECK_UNDERFLOW): New var, also off by default: whether to check
for stack underflow when popping values.
(vm_engine): Don't declare object_count if we are not checking object
table accesses.
* libguile/vm-engine.h (CACHE_PROGRAM): Don't muck with object_count
if we are not checking object table accesses.
(CHECK_UNDERFLOW, PRE_CHECK_UNDERFLOW): Nop out if we are not checking
underflow.
(POP2, POP3): New macros which check for underflow before popping more
than one value.
* libguile/vm-i-loader.c (load_array):
* libguile/vm-i-scheme.c (set_car, set_cdr, vector_set, slot_set)
(BV_SET_WITH_ENDIANNESS, BV_FIXABLE_INT_SET, BV_INT_SET)
(BV_FLOAT_SET):
* libguile/vm-i-system.c (partial_cont_call, fix_closure, prompt)
(fluid_set): Use POP2 / POP3.
(local_set, long_local_set): Pop to locals instead of using values on
the stack then dropping; allows for underflow to be checked before the
value is accessed.
(BR): Don't NULLSTACK or DROP after the operation.
(br_if, br_if_not, br_if_eq, br_if_not_eq, br_if_null)
(br_if_not_null): Pop to locals before doing the compare and jump.
* libguile/vm-i-system.c (new-frame): Though it was appealing to set the
dynamic link here on the incomplete frame, we no longer do that, for
the reasons mentioned in the code.
(call, mv-call): Adapt to set the frame's dynamic link.
* libguile/vm-engine.c (vm_engine): Don't set dynamic link here, even
for boot program.
* libguile/frames.c (scm_frame_num_locals, scm_frame_local_ref)
(scm_frame_local_set_x): Fix up not-yet-active frame detection.
* libguile/vm-i-system.c (variable-ref, variable-set, variable-bound?):
Check that the argument is actually a variable. Thanks to Kevin
Holmes for the report.
* libguile/vm-engine.c (vm_engine): Error handling down here.
* THANKS: Update.
* libguile/fluids.c (scm_make_undefined_fluid, scm_fluid_unset_x)
(scm_fluid_bound_p): New functions.
(fluid_ref): New function; like scm_fluid_ref, but will not throw an
error for unbound fluids.
(scm_fluid_ref, swap_fluid): Use `fluid_ref'.
* libguile/fluids.h (scm_make_undefined_fluid, scm_fluid_unset_x)
(scm_fluid_bound_p): New prototypes.
* libguile/vm-i-system.c (fluid_ref): If fluid is unbound, jump to
`vm_error_unbound_fluid'.
* libguile/vm-engine.c (VM_NAME)[vm_error_unbound_fluid]: New error
message.
* test-suite/tests/fluids.test ("unbound fluids")["fluid-ref of unbound
fluid", "fluid-bound? of bound fluid", "fluid-bound? of unbound
fluid", "unbound fluids can be set", "bound fluids can be unset"]: New
tests.
* libguile/vm-i-system.c (variable-ref, toplevel-ref)
(long-toplevel-ref): Fixup callers.
* libguile/vm-engine.c (vm_error_unbound): Don't use vm-error for
unbound vars, use misc-error. Don't include VM: in the string. Take
the name directly in finish_args, not as a list.
* libguile/vm-i-system.c (VM_DEFINE_INSTRUCTION): Drop the stack items
corresponding the the with-fluids object. Thanks very much to Stefan
Israelsson Tampe for the fix.
* libguile/vm-i-scheme.c (symbol?, vector?): New
instructions. Renumbered the rest.
* libguile/vm-i-system.c: Renumber instructions.
* libguile/_scm.h (SCM_OBJCODE_MINOR_VERSION): Bump.
* module/ice-9/psyntax.scm (binding-type, binding-value): Define using
macros so that we inline to car and cdr opcodes. Oh, for an inliner :)
* module/language/tree-il/compile-glil.scm (*primcall-ops*)
* module/language/tree-il/primitives.scm
(*interesting-primitive-names*, *effect-free-primitives*)
(*effect+exception-free-primitives*): Add symbol? and vector?
inlines.
* libguile/vm-i-system.c (call_cc, tail_call_cc): Call the new
RESTORE_CONTINUATION_HOOK when a continuation is restored.
(prompt): Call the new ABORT_CONTINUATION_HOOK when entering the abort
handler's continuation.
* libguile/vm-engine.h (ABORT_CONTINUATION_HOOK)
(RESTORE_CONTINUATION_HOOK):
* libguile/vm.h (SCM_VM_ABORT_CONTINUATION_HOOK)
(SCM_VM_RESTORE_CONTINUATION_HOOK):
* libguile/vm.c: (scm_vm_abort_continuation_hook): New hook, called when
entering an abort handler.
(scm_vm_restore_continuation_hook): New hook, called after returning
to a continuation.
* module/system/vm/vm.scm: Add hooks to export list.
* libguile/vm.h (SCM_VM_PUSH_CONTINUATION_HOOK)
(SCM_VM_POP_CONTINUATION_HOOK): New hooks, to replace
enter/exit/return.
(SCM_VM_BOOT_HOOK, SCM_VM_HALT_HOOK, SCM_VM_BREAK_HOOK): Remove these
useless hooks.
* libguile/vm.c (scm_vm_push_continuation_hook)
(scm_vm_pop_continuation_hook): New accessors.
* libguile/vm-i-system.c: Remove boot, halt, break, enter, exit, and
return hooks. Also remove the break instruction. Instead now when we
push a new continuation onto the stack we call PUSH_CONTINUATION_HOOK,
and when we pop via a return we call POP_CONTINUATION_HOOK. APPLY_HOOK
is now decoupled from continuation pushes and pops.
* libguile/vm-engine.h:
* libguile/vm-engine.c: Adapt for hooks.
* module/system/vm/trace.scm (vm-trace): Adapt for hooks. Also revive
the #:instructions? #t mode.
* module/system/vm/vm.scm: Adapt exports for new set of hooks.
