* libguile/Makefile.am: add new header file setjump-win.h
* libguile/continuations.h, libguile/dynstack.c, libguile/dynstack.h,
libguile/intrinsics.h, libguile/vm.h:
supply custom `setjmp` macro on Windows
Mingw implements `setjmp (env)` as a macro that expands to
_setjmp (env, faddr)
where `faddr` is set to the current frame address.
This address is then stored as first element in the jump buffer `env`.
When `longjmp` is called, it tries to unwind the stack up
to the saved address by calling `RtlUnwindEx` from MSVCRT,
which will fail, if the stack frames are interwoven with
JIT-generated code, that violate the Windows x64 calling conventions.
Thus implement the macro ourselves as
_setjmp (env, NULL)
which will toggle a code path in `longjmp` that does no unwinding.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
* libguile/jit.c (emit_alloc_frame_for_sp):
* libguile/vm-engine.c (ALLOC_FRAME, RESET_FRAME):
* libguile/vm.c (vm_increase_sp, scm_i_vm_prepare_stack):
(return_unused_stack_to_os, vm_expand_stack, alloc_frame):
(scm_call_with_stack_overflow_handler):
* libguile/vm.h (struct scm_vm): Remove sp_min_since_gc handling. It
was a very minor optimization when it was centralized in vm.c, but now
with JIT it's causing too much duplicate code generation.
* libguile/vm.c (scm_i_vm_emergency_abort): New helper: an abort that
doesn't allocate, not even stack.
* libguile/throw.c (abort_to_prompt): Use scm_i_vm_emergency_abort.
* libguile/vm.h: Declare helper.
* libguile/vm.h (SCM_VM_NUM_HOOKS): Remove hook enumeration.
(struct scm_vm): Re-arrange members to be more dense and to use common
cache lines for commonly-used members. Declare hooks and their enabled
flags by name.
* libguile/vm-engine.c (RUN_HOOK): Refer to hooks by name.
* libguile/vm.c (FOR_EACH_HOOK): New helper.
(vm_hook_compute_enabled, vm_recompute_disable_mcode): New routines to
recompute when hooks are enabled, and whether to disable mcode because
hooks are active.
(set_vm_trace_level): New helper.
(invoke_hook): Take hook to invoke by value.
(DEFINE_INVOKE_HOOK): Refactor to use named hooks.
(scm_i_vm_prepare_stack): Init named hooks.
(VM_ADD_HOOK, VM_REMOVE_HOOK): Refactor to use named hooks, and also
recompute global disable_mcode flag.
(scm_set_vm_trace_level_x, scm_c_set_vm_engine_x): Use internal helper.
* libguile/vm.h (SCM_VM_ABORT_HOOK): Rename from
SCM_VM_ABORT_CONTINUATION_HOOK.
* libguile/vm-engine.c (ABORT_HOOK):
* libguile/vm.c (invoke_abort_hook): Adapt to SCM_VM_ABORT_HOOK name
change.
(reset_vm_hook_enabled): New helper.
(VM_ADD_HOOK, VM_REMOVE_HOOK): New helper macros, replacing
VM_DEFINE_HOOK.
(scm_vm_add_abort_hook_x, scm_vm_remove_abort_hook_x)
(scm_vm_add_apply_hook_x, scm_vm_remove_apply_hook_x)
(scm_vm_add_return_hook_x, scm_vm_remove_return_hook_x)
(scm_vm_add_next_hook_x, scm_vm_remove_next_hook_x): New functions,
replacing direct access to the hooks. Allows us to know in a more
fine-grained way when to enable hooks.
(scm_set_vm_trace_level_x): Use reset_vm_hook_enabled to update the
individual hook_enabled flags.
* module/statprof.scm:
* module/system/vm/coverage.scm:
* module/system/vm/traps.scm:
* module/system/vm/vm.scm: Adapt VM hook users to the new API.
* libguile/continuations.c (scm_i_continuation_to_frame): Adapt to vra
field renaming.
(scm_i_reinstate_continuation, grow_stack, copy_stack_and_call)
(scm_dynthrow): Take mra of continuation. Set on the vp before the
longjmp.
* libguile/continuations.h: Update scm_i_reinstate_continuation
prototype.
* libguile/dynstack.h:
* libguile/control.c (scm_suspendable_continuation_p):
* libguile/dynstack.c (PROMPT_WORDS, PROMPT_VRA, PROMPT_MRA):
(PROMPT_JMPBUF, scm_dynstack_push_prompt, scm_dynstack_find_prompt)
(scm_dynstack_wind_prompt): Store both virtual and machine return
addresses on the dynstack, for prompts.
* libguile/eval.c (eval): Pass NULL for mra.
* libguile/intrinsics.c (push_prompt): Add mra arg, and pass it to the
dynstack.
* libguile/intrinsics.h: Update prototypes so that continuation-related
intrinsics can save and restore the MRA.
* libguile/jit.h:
* libguile/jit.c: Return VRA when JIT code needs to tier down.
* libguile/stacks.c (find_prompt, scm_make_stack)
* libguile/throw.c (catch): Adapt find-prompt calls.
* libguile/vm-engine.c (instrument-entry, instrument-loop): Add logic to
continue with vcode after the mcode finishes.
(compose-continuation, capture-continuation, abort, prompt): Add logic
to pass NULL as captured MRA, but continue with mcode from new
continuations, if appropriate.
* libguile/vm.c (scm_i_vm_cont_to_frame, capture_stack)
(scm_i_capture_current_stack, reinstate_continuation_x)
(capture_continuation, compose_continuation_inner, compose_continuation)
(capture_delimited_continuation, abort_to_prompt): Adapt to plumb
around machine code continuations.
(scm_call_n): Check "mra_after_abort" field for machine code
continuation, if any.
* libguile/vm.h (struct scm_vm): Add "mra_after_abort" field.
(struct scm_vm_cont): Rename "ra" field to "vra" and add "mra" field.
* libguile/frames.c (scm_frame_return_values): New function, for use
when a frame is at "return-values".
(scm_init_frames_builtins): Register frame-return-values.
* libguile/vm-engine.c (RETURN_HOOK): Rename from POP_CONTINUATION_HOOK.
(call, call-label): Remove PUSH_CONTINUATION_HOOK; it's unneeded, as
you can always check the FP from an apply hook.
(return-values): Run return hook before popping frame.
* libguile/vm.c (vm_dispatch_return_hook): Rename from
vm_dispatch_pop_continuation_hook. Remove push continuation hook.
(scm_vm_return_hook):
* libguile/vm.h (SCM_VM_PUSH_CONTINUATION_HOOK): Remove.
(SCM_VM_RETURN_HOOK): Rename from SCM_VM_POP_CONTINUATION_HOOK.
* module/system/vm/frame.scm (frame-return-values): Export.
* module/system/vm/trace.scm (print-return, trace-calls-to-procedure)
(trace-calls-in-procedure): Adapt to not receiving values as
arguments.
* module/system/vm/traps.scm (trap-in-procedure, trap-frame-finish):
Adapt to return hook coming from returning frame.
(program-sources-by-line): Update to use match instead of pmatch.
* module/system/vm/traps.scm (trap-in-dynamic-extent)
(trap-calls-to-procedure): Adapt to return hook not receiving values.
* module/system/vm/vm.scm: Remove push continuation hook and rename
return hook.
* libguile/control.c (scm_abort_to_prompt_star)
* libguile/throw.c (abort_to_prompt): Pass prompt tag and argv in one
array.
* libguile/vm.c (scm_i_vm_abort): Reimplement as a call into the VM's
abort_to_prompt builtin.
(vm_abort): New helper, a copy of scm_i_vm_abort. Will allow us to
avoid some arg shuffling when aborting from the VM.
* libguile/vm.h: Remove setjmp include and simplify scm_i_vm_abort
decl.
* libguile/control.h:
* libguile/control.c (scm_i_make_composable_continuation): Rename from
make_partial_continuation and expose internally.
(scm_abort_to_prompt_star): Adapt to scm_i_vm_abort name change.
* libguile/intrinsics.h (SCM_FOR_ALL_VM_INTRINSICS): Define
abort_to_prompt intrinsic.
* libguile/throw.c (abort_to_prompt): Adapt to scm_i_vm_abort name
change.
* libguile/vm-engine.c (abort): Use abort_to_prompt intrinsic.
* libguile/vm.c (capture_delimited_continuation): Move here from
control.c where it was named reify_partial_continuation.
(scm_i_vm_abort): Move from control.c where it was named
scm_c_abort (and only exposed internally).
(abort_to_prompt): New intrinsic, replacing vm_abort.
* libguile/vm.h: Add setjmp include and scm_i_vm_abort decl.
* libguile/threads.c (thread_mark): Unconditionally call
scm_i_vm_mark_stack.
(guilify_self_1): Eagerly prepare the thread stack, before entering
Guile mode. It's only a page of mmap, after all.
* libguile/vm.c (scm_i_vm_prepare_stack): Rename from init_vm.
(thread_vm, scm_the_vm): Remove.
(VM_DEFINE_HOOK, scm_vm_trace_level, scm_set_vm_trace_level_x)
(scm_vm_engine, scm_c_set_vm_engine_x, scm_i_capture_current_stack)
(scm_call_n, scm_call_with_stack_overflow_handler): Adapt to get VM
from thread.
(scm_i_vm_free_stack): Memset the whole thing to 0 when we're done.
* libguile/control.c (scm_abort_to_prompt_star)
* libguile/eval.c (eval):
* libguile/throw.c (catch, abort_to_prompt): Get VM from thread.
As the FSF advises, 'There is no legal significance to using the
three-character sequence “(C)”, but it does no harm.' It does take up
space though! For that reason, we remove it here from our C files.
* libguile/bytevectors.h: Include uniform.h, for use in the macros.
* libguile/extensions.h: Include libpath.h, for the
SCM_EFFECTIVE_VERSION, which is almost always used with these
routines.
* libguile/frames.h:
* libguile/instructions.h:
* libguile/intrinsics.h:
* libguile/loader.h:
* libguile/programs.h:
* libguile/vm.h: Include <libguile/__scm.h> instead of <libguile.h>.
Cuts a circular include, but also precipitates a lot of maintenance in
the .c files.
* libguile/*.c: Update C files to add needed all needed includes that
before were getting automatically pulled in by the indirect inclusion
of libguile.h.
Adapt VM stack to grow downward. This will make native compilation look
more like the VM code, as we will be able to use native CALL
instructions, taking proper advantage of the return address buffer.
* libguile/continuations.c (scm_i_continuation_to_frame): Record offsets
from stack top.
* libguile/control.c (scm_i_prompt_pop_abort_args_x): Adapt for reversed
order of arguments, and instead of relying on the abort to push on the
number of arguments, make the caller save the stack depth, which
allows us to compute the number of arguments ourselves.
(reify_partial_continuation, scm_c_abort): Adapt to reversed stack
order.
* libguile/dynstack.c (scm_dynstack_wind_prompt): Since we wind the
stack in a downward direction, subtract the reloc instead of adding
it.
* libguile/dynstack.h (SCM_F_DYNSTACK_PROMPT_ESCAPE_ONLY): Remove flag;
instead rely on prompt-establishing code to save the stack depth.
* libguile/eval.c (eval): Remove extraneous "volatile" declarations for
variables that are not re-set between the setjmp and any longjmp.
Adapt to save stack depth before instating the prompt.
* libguile/foreign.c (scm_i_foreign_call): Adapt to receive arguments in
reverse order.
* libguile/frames.c (frame_stack_top, scm_i_frame_stack_top): Adapt to
compute stack top instead of stack bottom.
(scm_c_frame_closure): Adapt to stack growth change.
(scm_frame_num_locals, scm_frame_local_ref, scm_frame_set_x): Use
union data type to access stack.
(RELOC): Reformat.
(scm_c_frame_previous): Adapt to stack growth change.
* libguile/frames.h: Adapt stack diagram to indicate that the stack
grows up.
(union scm_vm_stack_element): New data type used to access items on
the stack.
(SCM_FRAME_PREVIOUS_SP)
(SCM_FRAME_RETURN_ADDRESS, SCM_FRAME_SET_RETURN_ADDRESS)
(SCM_FRAME_DYNAMIC_LINK, SCM_FRAME_SET_DYNAMIC_LINK)
(SCM_FRAME_LOCAL, SCM_FRAME_NUM_LOCALS): Adapt to stack representation
change.
(SCM_FRAME_SLOT): New helper.
(SCM_VM_FRAME_FP, SCM_VM_FRAME_SP): Adapt to stack growth change.
* libguile/stacks.c (scm_make_stack): Record offsets from top of stack.
* libguile/throw.c (catch): Adapt to scm_i_prompt_pop_abort_args_x
change.
* libguile/vm-engine.c (ALLOC_FRAME, RESET_FRAME):
(FRAME_LOCALS_COUNT_FROM): Adapt to stack growth change.
(LOCAL_ADDRESS): Use SCM_FRAME_SLOT to get the address as the proper
data type.
(RETURN_ONE_VALUE, RETURN_VALUE_LIST): Adapt to stack growth change.
(apply): Shuffling up the SMOB apply args can cause the stack to
expand, so use ALLOC_FRAME instead of RESET_FRAME.
(vm_engine): Adapt for stack growth change.
* libguile/vm.c (vm_increase_sp, vm_push_sp, vm_restore_sp): Adapt to
stack representation change.
(scm_i_vm_cont_to_frame): Adapt to take offsets from the top.
(scm_i_vm_capture_stack): Adapt to capture from the top.
(vm_return_to_continuation_inner): Adapt for data type changes.
(vm_return_to_continuation): Likewise, and instead of looping, just
splat the saved arguments on with memcpy.
(vm_dispatch_hook): Adapt to receive arguments in the reverse order.
Adapt callers.
(vm_abort): There is never a tail argument. Adapt to stack
representation change.
(vm_reinstate_partial_continuation)
(vm_reinstate_partial_continuation_inner): Adapt to stack growth
change.
(allocate_stack, free_stack): Adapt to data type change.
(expand_stack): Don't try to mremap(), as you can't grow a mapping
from the bottom. Without knowing that there's a free mapping space
right below the old stack, which there usually isn't on Linux, we have
to copy. We can't use MAP_GROWSDOWN because Linux is buggy.
(make_vm): Adapt to stack representation changes.
(return_unused_stack_to_os): Round down instead of up, as the stack
grows down.
(scm_i_vm_mark_stack): Adapt to walk up the stack.
(scm_i_vm_free_stack): Adapt to scm_vm changes.
(vm_expand_stack_inner, reset_stack_limit, vm_expand_stack): Adapt to
the stack growing down.
(scm_call_n): Adapt to the stack growing down. Don't allow argv to
point into the stack.
* libguile/vm.h (struct scm_vm, struct scm_vm_cont): Adapt to hold the
stack top and bottom.
* libguile/stacks.c (scm_make_stack, scm_stack_id):
* libguile/vm.c (scm_i_vm_cont_to_frame): Allow delimited continuations
as the argument to make-stack.
* libguile/vm.h:
* libguile/vm.c (default_max_stack_size, initialize_default_stack_size):
Remove the default stack limit. In this way, programs run from the
command line or outside of the REPL will have no soft stack limit.
(make_vm): Change `max_stack_size' field to be a stack of limits and
handlers.
(current_overflow_size, should_handle_stack_overflow)
(reset_stack_limit, wind_overflow_handler, unwind_overflow_handler)
(vm_expand_stack): If the stack surpasses a user-set limit, call the
user-specified handler within its outer stack limit.
(call-with-stack-overflow-handler): New interface.
* module/system/vm/vm.scm: Export call-with-stack-overflow-handler.
* libguile/vm.h (struct scm_vm): Reorder fields. Add "sp_max_since_gc"
field.
* libguile/vm-engine.c (ALLOC_FRAME, RESET_FRAME):
* libguile/vm.c (vm_return_to_continuation)
(vm_reinstate_partial_continuation, scm_call_n): In places where we
could increase the stack height, update sp_max_since_gc.
(vm_expand_stack): Relocate sp_max_since_gc on expansion.
(scm_bootstrap_vm): Record the page size using gnulib's getpagesize.
(return_unused_stack_to_os): New routine, run when marking stacks.
* libguile/vm-engine.c (CHECK_OVERFLOW): Call vm_expand_stack, not
vm_error_stack_overflow.
* libguile/vm.c (hard_max_stack_size, default_max_stack_size): Recast
#defines as locals. Have both hard and soft stack limits.
(initialize_default_stack_size): Set soft stack limit from
GUILE_STACK_SIZE.
(expand_stack, vm_expand_stack): Support for expanding stacks as
needed. Whee!
(make_vm): Adapt limits.
(scm_call_n): Expand stack if needed.
* libguile/vm.h (struct scm_vm): Add max_stack_size member.
* libguile/threads.c (thread_mark): Mark the VM stack, if we have one.
(on_thread_exit): Free the VM stack here.
* libguile/vm.c (make_vm): Allocate the VM stack using mmap, and arrange
for it to be marked by the thread marker.
(scm_i_vm_mark_stack, scm_i_vm_free_stack): New internal interfaces.
(allocate_stack, free_stack): New helpers.
* libguile/vm.h:
* libguile/vm.c:
(scm_vm_apply_hook, scm_vm_push_continuation_hook,
scm_vm_pop_continuation_hook, scm_vm_abort_continuation_hook,
scm_vm_restore_continuation_hook, scm_vm_next_hook,
scm_vm_trace_level, scm_set_vm_trace_level_x, scm_vm_engine,
scm_set_vm_engine_x, scm_c_set_vm_engine_x): The VM argument is now
implicit: the VM for the current thread.
* doc/ref/api-debug.texi (VM Hooks): Try to adapt.
* module/ice-9/command-line.scm:
* module/statprof.scm:
* module/system/vm/coverage.scm:
* module/system/vm/trace.scm:
* module/system/vm/trap-state.scm:
* module/system/vm/traps.scm:
* test-suite/tests/control.test:
* test-suite/tests/eval.test: Adapt users that set hooks or ensure that
we have a debug engine.
* libguile/vm-engine.c:
* libguile/vm.c: Rework VM inclusion so that we don't define VM_ENGINE
and expect vm-engine.c to understand that -- since there is only
VM_USE_HOOKS, define that in vm.c directly. Rename rtl_vm_foo to
vm_foo.
* libguile/vm.h: Remove scm_t_vm_engine typedef.
* libguile/frames.h (SCM_FRAME_RTL_RETURN_ADDRESS)
(SCM_FRAME_SET_RTL_RETURN_ADDRESS): Remove. The variants without _RTL
now work fine.
(struct scm_vm_frame): Change the return address to be a
scm_t_uint32*.
(struct scm_frame): Change IP to be scm_t_uint32*.
* libguile/frames.c (scm_c_make_frame)
* libguile/control.c (reify_partial_continuation, scm_c_abort)
* libguile/dynstack.c (PROMPT_IP)
(scm_dynstack_push_prompt, scm_dynstack_find_prompt)
* libguile/dynstack.h:
* libguile/vm-engine.c (SYNC_IP, RETURN_ONE_VALUE)
(call, return-values, prompt): Adapt.
* libguile/Makefile.am:
* libguile/vm-builtins.h: New header, declaring stubs needed by the
compiler like values, apply, and abort-to-prompt.
* libguile/vm.c: Adapt the apply and values stubs to conform to a
standard interface. Add an abort-to-prompt stub. Add call/cc and
call-with-values stubs.
(scm_vm_builtin_ref): New helper, for the builtin-ref opcode.
(scm_vm_builtin_name_to_index)
(scm_vm_builtin_index_to_name): New helpers, for the compiler and
disassembler, respectively.
(scm_init_vm_builtins, scm_bootstrap_vm): Allow the compiler helpers
to be loaded later into a module.
* module/language/rtl.scm: Export builtin-index->name and
builtin-name->index.
* libguile/vm-engine.c (RETURN_VALUE_LIST): Update to use new names of
"apply" and "values".
(tail-call/shuffle): New opcode.
(abort): Update to be a tail VM op, and reorder and renumber other
ops.
(builtin-ref): New opcode.
* libguile/continuations.h:
* libguile/continuations.c (scm_i_call_with_current_continuation):
Move this to vm.[ch], implemented as a builtin.
* module/language/tree-il/compile-cps.scm (convert): Convert to
'abort-to-prompt calls, possibly with 'apply, effectively undoing the
tree-il transformation.
* module/language/cps/reify-primitives.scm (builtin-ref): New helper.
(reify-primitives): Convert builtin primitives to builtin-ref.
* module/language/cps/dfg.scm (constant-needs-allocation?):
* module/language/cps/compile-rtl.scm (emit-rtl-sequence): Add support
for compiling builtin-ref.
* module/system/vm/disassembler.scm (code-annotation): Add annotation
for builtin-ref.
* 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/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/vm.h (scm_c_vm_run): Make internal.
* libguile/vm.c (vm_default_engine): New static global variable.
(make_vm): Set vp->engine based on
(scm_vm_apply): Remove in favor of call-with-vm.
(scm_thread_vm, scm_set_thread_vm_x): Remove these, as they did not
have a well-defined meaning, and were dangerous to call on other
threads.
(scm_the_vm): Reinstate previous definition.
(symbol_to_vm_engine, vm_engine_to_symbol)
(vm_has_pending_computation): New helpers.
(scm_vm_engine, scm_set_vm_engine_x, scm_c_set_vm_engine_x): New
accessors for VM engines.
(scm_c_set_default_vm_engine_x, scm_set_default_vm_engine_x): New
setters for the default VM engine.
(scm_call_with_vm): New function, applies a procedure to arguments in
a context in which a given VM is current.
* libguile/eval.c (eval, scm_apply): VM dispatch goes through
scm_call_with_vm.
* test-suite/tests/control.test ("the-vm"):
* module/system/vm/coverage.scm (with-code-coverage): Use call-with-vm.
* module/system/vm/vm.scm: Update exports.
* test-suite/vm/run-vm-tests.scm (run-vm-program):
* test-suite/tests/compiler.test ("current-reader"): Just rely on the
result of make-program being an applicable.
* test-suite/tests/eval.test ("stack overflow"): Add a note that this
test does not test what it should.
