* libguile/frames.h (struct scm_frame): stack_holder is a void*.
* libguile/frames.c (scm_i_frame_stack_base, scm_i_frame_offset): Expect
stack_holder to be the raw struct scm_vm or scm_vm_cont.
* libguile/continuations.c (scm_i_continuation_to_frame):
* libguile/stacks.c (scm_make_stack)
* libguile/vm.c (vm_dispatch_hook): Adapt creators.
* libguile/frames.h (enum scm_vm_frame_kind, SCM_VM_FRAME_KIND)
(scm_c_make_frame): Add a "frame kind" bit to the first word. This
will allow the "stack holder" to be a non-SCM object.
* libguile/continuations.c (scm_i_continuation_to_frame):
* libguile/frames.c (scm_c_make_frame, scm_frame_previous)
* libguile/stacks.c (scm_make_stack):
* libguile/vm.c (vm_dispatch_hook): Adapt frame creators to set the
frame kind bit.
* libguile/frames.h: Wrap the C interface to VM frames in
BUILDING_LIBGUILE. Change VM frames to record relative offsets into a
stack held by some other object, so that if the stack moves they will
remain valid.
* libguile/frames.c (scm_c_make_frame): Remove offset argument.
(scm_i_frame_offset): Instead, compute the offset from the stack
holder.
(scm_i_frame_stack_base): New helper.
(scm_frame_previous): Adapt.
* libguile/stacks.c (scm_make_stack)
* libguile/vm.c (vm_dispatch_hook):
* libguile/continuations.c (scm_i_continuation_to_frame): 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/continuations.h:
* libguile/continuations.c: Reimplement continuations and the call_cc
stub as RTL programs.
* libguile/programs.c (scm_i_rtl_program_minimum_arity): Add a case for
continuations.
* libguile/vm-engine.c (rtl_vm_debug_engine): Always call the abort
continuation hook with the number of non-procedure locals. Fix
compose-continuation argument count. Enable call/cc.
* 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/control.c:
* libguile/continuations.c: Fix for the case in which SCM_ALIGNED is not
defined. Though I wonder, perhaps we should just error out in those
cases.
* libguile/ports.c (scm_putc, scm_puts):
* libguile/ports.h (scm_putc_unlocked, scm_puts_unlocked): Separate into
_unlocked and locked variants. Change all callers to use the
_unlocked versions.
* libguile/tags.h (SCM_UNPACK_POINTER, SCM_PACK_POINTER): New macros.
The old SCM2PTR and PTR2SCM were defined in such a way that
round-tripping through a pointer could lose precision, even in the
case in which you weren't interested in actually dereferencing the
pointer, it was simply that you needed to plumb a SCM through APIs
that take pointers. These new macros are more like SCM_PACK and
SCM_UNPACK, but for pointer types. The bit representation of the
pointer should be the same as the scm_t_bits representation.
* libguile/gc.h (PTR2SCM, SCM2PTR): Remove support for (old) UNICOS
pointers. We are going to try tagging the SCM object itself in the
future, and I don't think that keeping this support is worth its
cost. It probably doesn't work anyway.
* libguile/backtrace.c:
* libguile/bytevectors.c:
* libguile/continuations.c:
* libguile/fluids.c:
* libguile/foreign.c:
* libguile/gc.h:
* libguile/guardians.c:
* libguile/hashtab.c:
* libguile/load.c:
* libguile/numbers.c:
* libguile/ports.c:
* libguile/smob.c:
* libguile/strings.c:
* libguile/symbols.c:
* libguile/vm.c:
* libguile/weak-set.c:
* libguile/weak-table.c:
* libguile/weak-vector.c: Update many sites to use the new macros.
* libguile/continuations.c (scm_handler, c_handler)
(scm_c_with_continuation_barrier, scm_with_continuation_barrier):
Instead of calling scm_handle_by_message_noexit in the pre-unwind
handler, roll our own exception printing in the pre-unwind, and do to
exit()-on-quit in the post-unwind handler. This lets the stack unwind
at exit-time so that pending dynwinds run.
* test-suite/tests/continuations.test ("continuations"): Add a test.
* libguile/continuations.c (scm_handler, c_handler)
(scm_c_with_continuation_barrier, scm_with_continuation_barrier): Call
scm_handle_by_message_noexit in the post-unwind handler, so that
dynwinds
* test-suite/tests/continuations.test ("continuations"): Add a test.
* libguile/objcodes.h (SCM_OBJCODE_TYPE_MMAP)
(SCM_OBJCODE_TYPE_BYTEVECTOR, SCM_OBJCODE_TYPE_SLICE)
(SCM_OBJCODE_TYPE_STATIC): Enumerate objcode types instead of
expressing them as flags.
(SCM_OBJCODE_TYPE): Type is held in bits 8-15.
(SCM_OBJCODE_FLAGS): Flags are now shifted by 16 bits, not 8.
(SCM_MAKE_OBJCODE_TAG): New helper.
* libguile/continuations.c (STATIC_OBJCODE_TAG):
* libguile/control.c (STATIC_OBJCODE_TAG):
* libguile/foreign.c (STATIC_OBJCODE_TAG):
* libguile/gsubr.c (STATIC_OBJCODE_TAG):
* libguile/smob.c (STATIC_OBJCODE_TAG):
* libguile/objcodes.c (make_objcode_by_mmap, scm_c_make_objcode_slice)
(scm_bytecode_to_objcode): : Use SCM_MAKE_OBJCODE_TAG.
* libguile/vm.h (struct scm_vm_cont): Instead of saving the "IP", save
"RA" and "MVRA". That is, save singly-valued and multiply-valued
return addresses, so that we can return multiple values on the stack.
(scm_i_vm_reinstate_continuation): Remove.
* libguile/vm.c (vm_capture_continuation): Rename from capture_vm_cont,
and change the prototype so we can capture the RA and MVRA, and so
that tail calls to call/cc can capture a continuation without the
call/cc application frame.
(vm_return_to_continuation): Rename from reinstate_vm_cont, and take
arguments to return to the continuation. Handles returning to single
or multiple-value RA.
(scm_i_vm_capture_continuation): Change to invoke
vm_capture_continuation. Kept around for the benefit of make-stack.
* libguile/vm-i-system.c (continuation-call): Handle reinstatement of
the VM stack, with arguments.
(call/cc, tail-call/cc): Adapt to new vm_capture_continuation
prototype. tail-call/cc captures tail continuations.
* libguile/stacks.c (scm_make_stack): Update for scm_vm_cont structure
change.
* libguile/continuations.h (struct scm_contregs): Remove throw_value
member, which was used to return a value to a continuation.
(scm_i_check_continuation): New internal function, checks that a
continuation may be reinstated.
(scm_i_reinstate_continuation): Replaces scm_i_continuation_call; just
reinstates the C stack.
(scm_i_contregs_vm, scm_i_contregs_vm_cont): New internal accessors.
* libguile/continuations.c (scm_i_make_continuation): Return
SCM_UNDEFINED if we are returning again.
(grow_stack, copy_stack_and_call, scm_dynthrow): Remove extra arg, as
vm opcodes handle value returns.
(copy_stack): No need to instate VM continuation.
(scm_i_reinstate_continuation): Adapt.
* libguile/continuations.h:
* libguile/continuations.c (scm_i_make_continuation): Take VM and VM
continuation arguments as well; I'm not convinced that saving all VM
continuations was the right thing, and in any case we only ever saved
the latest. Running a new VM should create a continuation barrier.
* libguile/stacks.c (scm_make_stack):
* libguile/vm-i-system.c (call/cc, tail-call/cc): Adapt callers.
* libguile/vm.h (scm_i_vm_capture_continuation)
(scm_i_vm_reinstate_continuation): Change to be internal, and to only
capture and reinstate continuations for a particular VM.
* libguile/continuations.h
* libguile/continuations.c (scm_i_call_with_current_continuation): New
internal function. Not exported because I'm not sure whether or not
this should have a continuation barrier in the future. Uses a
hand-coded VM procedure.
* libguile/eval.c (eval): Use scm_i_call_with_current_continuation.
* libguile/vm-i-system.c (continuation-call): New op, like subr-call or
foreign-call, but for continuations.
* libguile/continuations.h: Add scm_i_continuation_call internal
declaration.
(SCM_CONTINUATIONP): Reimplement in terms of
SCM_PROGRAM_IS_CONTINUATION.
(scm_tc16_continuation, SCM_CONTREGS, SCM_CONTINUATION_LENGTH)
(SCM_SET_CONTINUATION_LENGTH, SCM_JMPBUF, SCM_DYNENV, SCM_THROW_VALUE)
(SCM_CONTINUATION_ROOT, SCM_DFRAME): Remove these from the exposed
API.
(scm_i_continuation_to_frame): New internal declaration.
* libguile/continuations.c
* libguile/continuations.c: Add trickery like in foreign.c, smob.c, and
gsubr.c, so that we can make procedural trampolines for continuations.
(scm_i_continuation_to_frame): New internal function, from stacks.c.
* libguile/programs.h (SCM_F_PROGRAM_IS_CONTINUATION)
(SCM_PROGRAM_IS_CONTINUATION): Add a flag for programs that are
continuations. Probably should add flags for the other trampoline
types too.
* libguile/programs.c (scm_i_program_print): Print continuations as
before.
* libguile/stacks.c (scm_stack_id, scm_make_stack): Use
scm_i_continuation_to_frame in the continuation case.
* libguile/debug.h (scm_t_debug_frame): Remove this type, as it was
internal to the old evaluator.
(SCM_EVALFRAME, SCM_APPLYFRAME, SCM_VOIDFRAME, SCM_MACROEXPF)
(SCM_TAILREC, SCM_TRACED_FRAME, SCM_ARGS_READY, SCM_DOVERFLOW)
(SCM_MAX_FRAME_SIZE, SCM_FRAMETYPE)
(SCM_EVALFRAMEP, SCM_APPLYFRAMEP, SCM_VOIDFRAMEP, SCM_MACROEXPFP)
(SCM_TAILRECP, SCM_TRACED_FRAME_P, SCM_ARGS_READY_P, SCM_OVERFLOWP)
(SCM_SET_MACROEXP, SCM_SET_TAILREC, SCM_SET_TRACED_FRAME)
(SCM_SET_ARGSREADY, SCM_SET_OVERFLOW)
(SCM_CLEAR_MACROEXP, SCM_CLEAR_TRACED_FRAME, SCM_CLEAR_ARGSREADY):
Remove macro accessors to scm_t_debug_frame.
(SCM_DEBUGOBJP, SCM_DEBUGOBJ_FRAME, SCM_SET_DEBUGOBJ_FRAME):
(scm_debug_object_p, scm_make_debugobj): Remove debugobj accessors.
(scm_i_unmemoize_expr): Remove unused declaration.
* libguile/debug.c (scm_debug_options): No more max limit on frame
sizes.
(scm_start_stack): Just call out to scm_vm_call_with_new_stack.
(scm_debug_object_p, scm_make_debugobj, scm_init_debug): No more
debugobj smob type.
* libguile/deprecated.h:
* libguile/deprecated.c (scm_i_deprecated_last_debug_frame)
(scm_last_debug_frame): Remove deprecated debug-frame bits.
* libguile/stacks.c (scm_make_stack): Rework this function and its
dependents to only walk VM frames.
(scm_stack_id): Call out to the holder of the VM frame in question,
which should be a VM or a VM continuation, for the stack ID. Currently
this bit is stubbed out.
(scm_last_stack_frame): Removed. It seems this is mainly useful for a
debugger, and we need to rewrite the debugger to work on the Scheme
level.
* test-suite/tests/continuations.test ("continuations"): Remove test for
last-stack-frame.
* libguile/continuations.h (struct scm_t_contregs):
* libguile/continuations.c (scm_make_continuation):
(copy_stack_and_call, scm_i_with_continuation_barrier): No need to
save and restore debug frames.
* libguile/threads.h (scm_i_thread): Don't track debug frames.
(scm_i_last_debug_frame, scm_i_set_last_debug_frame): Remove macro
accessors.
* libguile/threads.c (guilify_self_1): Don't track debug frames.
* libguile/throw.c: No need to track debug frames in a jmpbuf.
* libguile/vm-engine.c (vm_engine, VM_PUSH_DEBUG_FRAMES): Don't push
debug frames.
* libguile/vm.h:
* libguile/vm.c (scm_vm_call_with_new_stack): New function. Currently
stubbed out though.
The crux of this problem was that the thread doing a throw, and so
checking scm_i_critical_section_level, was different from the thread
that was in a critical section.
* libguile/async.h (scm_i_critical_section_level): Removed, replaced
by per-thread critical_section_level.
(SCM_CRITICAL_SECTION_START, SCM_CRITICAL_SECTION_END): Use
per-thread critical_section_level.
* libguile/continuations.c (scm_dynthrow): Check per-thread
critical_section_level.
* libguile/threads.c (guilify_self_1): Init per-thread
critical_section_level.
(scm_i_critical_section_level): Removed.
* libguile/threads.h (scm_i_thread): New critical_section_level field.
* libguile/throw.c (scm_ithrow): Check per-thread critical_section_level.
Problem was that if an application includes both libguile.h and the
system's setjmp.h, and is compiled on IA64, it gets compile errors
because of jmp_buf, setjmp and longjmp being multiply defined.
* libguile/__scm.h (__ia64__): Define scm_i_jmp_buf, SCM_I_SETJMP and
SCM_I_LONGJMP instead of jmp_buf, setjmp and longjmp.
(all other platforms): Map scm_i_jmp_buf, SCM_I_SETJMP and
SCM_I_LONGJMP to jmp_buf, setjmp and longjmp.
* libguile/continuations.c (scm_make_continuation): Use `SCM_I_SETJMP'
instead of `setjmp'.
(copy_stack_and_call): Use `SCM_I_LONJMP' instead of `longjmp'.
(scm_ia64_longjmp): Use type `scm_i_jmp_buf' instead of `jmp_buf'.
* libguile/continuations.h (scm_t_contregs): Use type `scm_i_jmp_buf'
instead of `jmp_buf'.
* libguile/threads.c (suspend): Use `SCM_I_SETJMP' instead of
`setjmp'.
* libguile/threads.h (scm_i_thread): Use type `scm_i_jmp_buf' instead
of `jmp_buf'.
* libguile/throw.c (JBJMPBUF, make_jmpbuf, jmp_buf_and_retval): Use
type `scm_i_jmp_buf' instead of `jmp_buf'.
(scm_c_catch): Use `SCM_I_SETJMP' instead of `setjmp'.
(scm_ithrow): Use `SCM_I_LONGJMP' instead of `longjmp'.
Thanks to Juhani Rantanen for the report.
* libguile/continuations.c (scm_make_continuation): Delay making the smob
until the data is fully initialized. Fixes a bug whereby a GC in
scm_vm_capture_continuations would catch the us with an undefined
continuation->vm_conts, leading to marking badness.
* libguile/vm.c (vm_cont_free): Report the correct size to scm_gc_free.
* libguile/continuations.c (continuation_mark): Mark the vm
continuations.
* libguile/vm.c (vm_cont_mark): Fix the marking function.
(vm_mark): Fix this one too -- the size is a number of STACKITEMS,
which we foolishly assume are the same size as SCM.
* test-suite/tests/ftw.test: Make our stat hacks verifyable without
assuming that they are interpreted.
* test-suite/tests/r5rs_pitfall.test: Re-indent.
* libguile/continuations.c (scm_make_continuation): Capture VM
continuations as well, as their stack is outside the C stack.
(copy_stack): Reinstate VM stacks with the C stack.
* libguile/continuations.h (scm_t_contregs): Add a pointer for VM stacks.
A binary-incompatible change -- hopefully not too many people were
messing around with this struct, though.
* libguile/vm-engine.c (vm_run): Add a note about possibly maintaining a
stack of vms.
* libguile/vm.c (struct scm_vm_cont): New struct, distinct from scm_vm.
(vm_cont_mark, vm_cont_free, capture_vm_cont, reinstate_vm_cont):
Reorder some code, and fix some bad assumptions about what part of the
stack to copy; obviously this code was never used.
* libguile/vm.h:
* libguile/vm.c (scm_vm_capture_continuations)
(scm_vm_reinstate_continuations): New public functions, used by
continuations.c.
* Specific problems in IA64 make check
** test-unwind
Representation of the relevant dynamic context:
non-rewindable
catch frame make cont.
o----o-----a----------b-------------c
\
\ call cont.
o-----o-----------d
A continuation is captured at (c), with a non-rewindable frame in the
dynamic context at (b). If a rewind through that frame was attempted,
Guile would throw to the catch at (a). Then the context unwinds back
past (a), then winds forwards again, and the captured continuation is
called at (d).
We should end up at the catch at (a). On ia64, we get an "illegal
instruction".
The problem is that Guile does not restore the ia64 register backing
store (RBS) stack (which is saved off when the continuation is
captured) until all the unwinding and rewinding is done. Therefore,
when the rewind code (scm_i_dowinds) hits the non-rewindable frame at
(b), the RBS stack hasn't yet been restored. The throw finds the
jmp_buf (for the catch at (a)) correctly from the dynamic context, and
jumps back to (a), but the RBS stack is invalid, hence the illegal
instruction.
This could be fixed by restoring the RBS stack earlier, at the same
point (copy_stack) where the normal stack is restored. But that
causes a problem in the next test...
** continuations.test
The dynamic context diagram for this case is similar:
non-rewindable
catch frame make cont.
a----x-----o----------b-------------c
\
\ call cont.
o-------d
The only significant difference is that the catch point (a) is
upstream of where the dynamic context forks. This means that the RBS
stack at (d) already contains the correct RBS contents for throwing
back to (a), so it doesn't matter whether the RBS stack that was saved
off with the continuation gets restored.
This test passes with the Guile 1.8.4 code, but fails (with an
"illegal instruction") when the code is changed to restore the RBS
stack earlier as described above.
The problem now is that the RBS stack is being restored _too_ early;
specifically when there is still stuff to do that relies on the old
RBS contents. When a continuation is called, the sequence of relevant
events is:
(1) Grow the (normal) stack until it is bigger than the (normal)
stack saved off in the continuation. (scm_dynthrow, grow_stack)
(2) scm_i_dowinds calls itself recursively, such that
(2.1) for each rewind (from (x) to (c)) that will be needed,
another frame is added to the stack (both normal and RBS),
with local variables specifying the required rewind; the
rewinds don't actually happen yet, they will happen when
the stack unwinds again through these frames
(2.2) required unwinds - back from where the continuation was
called (d) to the fork point (x) - are done immediately.
(3) The normal (i.e. non-RBS) stack that was stored in the
continuation is restored (i.e. copied on top of the actual
stack).
Note that this doesn't overwrite the frames that were added in
(2.1), because the growth in (1) ensures that the added frames
are beyond the end of the restored stack.
(4) ? Restore the RBS stack here too ?
(5) Return (from copy_stack) through the (2.1) frames, which means
that the rewinds now happen.
(6) setcontext (or longjmp) to the context (c) where the
continuation was captured.
The trouble is that step (1) does not create space in the RBS stack in
the same kind of way that it does for the normal stack. Therefore, if
the saved (in the continuation) RBS stack is big enough, it can
overwrite the RBS of the (2.1) frames that still need to complete.
This causes an illegal instruction when we return through those frames
and try to perform the rewinds.
* Fix
The key to the fix is that the saved RBS stack only needs to be
restored at some point before the next setcontext call, and that doing
it as close to the setcontext call as possible will avoid bad
interactions with the pre-setcontext stack. Therefore we do the
restoration at the last possible point, immediately before the next
setcontext call.
The situation is complicated by there being two ways that the next
setcontext call can happen.
- If the unwinding and rewinding is all successful, the next
setcontext will be the one from step (6) above. This is the
"normal" continuation invocation case.
- If one of the rewinds throws an error, the next setcontext will
come from the throw implementation code. (And the one in step (6)
will never happen.) This is the rewind error case.
In the rewind error case, the code calling setcontext knows nothing
about the continuation. So to cover both cases, we:
- copy (in step (4) above) the address and length of the
continuation's saved RBS stack to the current thread state
(SCM_I_CURRENT_THREAD)
- modify all setcontext callers so that they check the current
thread state for a saved RBS stack, and restore it if so before
calling setcontext.
* Notes
** I think rewinders cannot rely on using any stack data
Unless it can be guaranteed that the data won't go into a register.
I'm not 100% sure about this, but I think it follows from the fact
that the RBS stack is not restored until after the rewinds have
happened.
Note that this isn't a regression caused by the current fix. In Guile
1.8.4, the RBS stack was restored _after_ the rewinds, and this is
still the case now.
** Most setcontext calls for `throw' don't need to change the RBS stack
In the absence of continuation invocation, the setcontext call in the
throw implementation code always sets context to a place higher up the
same stack (both normal and RBS), hence no stack restoration is
needed.
* Other changes
** Using setcontext for all non-local jumps (for __ia64__)
Along the way, I read a claim somewhere that setcontext was more
reliable than longjmp, in cases where the stack has been manipulated.
I don't now have any reason to believe this, but it seems reasonable
anyway to leave the __ia64__ code using getcontext/setcontext, instead
of setjmp/longjmp.
(I think the only possible argument against this would be performance -
if getcontext was significantly slower than setjmp. It that proves to
be the case, we should revisit this.)
** Capping RBS base for non-main threads
Somewhere else along the way, I hit a problem in GC, involving the RBS
stack of a non-main thread. The problem was, in
SCM_MARK_BACKING_STORE, that scm_ia64_register_backing_store_base was
returning a value that was massively greater than the value of
scm_ia64_ar_bsp, leading to a seg fault. This is because the
implementation of scm_ia64_register_backing_store_base is only valid
for the main thread. I couldn't find a neat way of getting the true
RBS base of a non-main thread, but one idea is simply to call
scm_ia64_ar_bsp when guilifying a thread, and use the value returned
as an upper bound for that thread's RBS base. (Note that the RBS
stack grows upwards.)
(Were it not for scm_init_guile, we could be much more definitive
about this. We could take the value of scm_ia64_ar_bsp as a
definitive base address for the part of the RBS stack that Guile cares
about. We could also then discard
scm_ia64_register_backing_store_base.)
* threads.c (SCM_MARK_BACKING_STORE): Use scm_ia64_ar_bsp() and
scm_ia64_register_backing_store_base() instead of Linux-specific
implementations.
* gc.h (scm_ia64_register_backing_store_base, scm_ia64_ar_bsp):
New declarations.
* gc.c (__libc_ia64_register_backing_store_base): Declaration
removed.
(scm_ia64_register_backing_store_base, scm_ia64_ar_bsp): New, with
implementations for Linux and HP-UX.
* coop-pthreads.c (SCM_MARK_BACKING_STORE): Use scm_ia64_ar_bsp()
and scm_ia64_register_backing_store_base() instead of
Linux-specific implementations.
* continuations.h (__libc_ia64_register_backing_store_base):
Declaration removed.
(scm_t_contregs): New "fresh" field.
* continuations.c (ia64_getcontext): Removed.
(scm_make_continuation): Use continuation fresh field instead of
interpreting getcontext return values (which isn't portable). Use
scm_ia64_ar_bsp() and scm_ia64_register_backing_store_base()
instead of Linux-specific implementations.
(copy_stack_and_call): Use scm_ia64_register_backing_store_base()
instead of Linux-specific implementation.
* _scm.h (__ia64__): Also detect __ia64.
