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"""
This file defines utilities for manipulating the stack in an
RPython-compliant way. It is mainly about the stack_check() function.
"""
import py
from rpython.rlib.objectmodel import we_are_translated, fetch_translated_config
from rpython.rlib.rarithmetic import r_uint
from rpython.rlib import rgc
from rpython.rtyper.lltypesystem import lltype, rffi
from rpython.rtyper.lltypesystem.lloperation import llop
# ____________________________________________________________
def llexternal(name, args, res, _callable=None):
return rffi.llexternal(name, args, res,
sandboxsafe=True, _nowrapper=True,
_callable=_callable)
_stack_get_end = llexternal('LL_stack_get_end', [], lltype.Signed,
lambda: 0)
_stack_get_length = llexternal('LL_stack_get_length', [], lltype.Signed,
lambda: 1)
_stack_set_length_fraction = llexternal('LL_stack_set_length_fraction',
[lltype.Float], lltype.Void,
lambda frac: None)
_stack_too_big_slowpath = llexternal('LL_stack_too_big_slowpath',
[lltype.Signed], lltype.Char,
lambda cur: '\x00')
# the following is used by the JIT
_stack_get_end_adr = llexternal('LL_stack_get_end_adr', [], lltype.Signed)
_stack_get_length_adr= llexternal('LL_stack_get_length_adr',[], lltype.Signed)
# the following is also used by the JIT: "critical code" paths are paths in
# which we should not raise StackOverflow at all, but just ignore the stack limit
_stack_criticalcode_start = llexternal('LL_stack_criticalcode_start', [],
lltype.Void, lambda: None)
_stack_criticalcode_stop = llexternal('LL_stack_criticalcode_stop', [],
lltype.Void, lambda: None)
def stack_check():
if not we_are_translated():
return
if fetch_translated_config().translation.reverse_debugger:
return # XXX for now
#
# Load the "current" stack position, or at least some address that
# points close to the current stack head
current = llop.stack_current(lltype.Signed)
#
# Load these variables from C code
end = _stack_get_end()
length = _stack_get_length()
#
# Common case: if 'current' is within [end-length:end], everything
# is fine
ofs = r_uint(end - current)
if ofs <= r_uint(length):
return
#
# Else call the slow path
stack_check_slowpath(current)
stack_check._always_inline_ = True
stack_check._dont_insert_stackcheck_ = True
@rgc.no_collect
def stack_check_slowpath(current):
if ord(_stack_too_big_slowpath(current)):
from rpython.rlib.rstackovf import _StackOverflow
raise _StackOverflow
stack_check_slowpath._dont_inline_ = True
stack_check_slowpath._dont_insert_stackcheck_ = True
def stack_almost_full():
"""Return True if the stack is more than 15/16th full."""
if not we_are_translated():
return False
# see stack_check()
current = llop.stack_current(lltype.Signed)
end = _stack_get_end()
length = 15 * (r_uint(_stack_get_length()) >> 4)
ofs = r_uint(end - current)
if ofs <= length:
return False # fine
else:
_stack_too_big_slowpath(current) # this might update the stack end
end = _stack_get_end()
ofs = r_uint(end - current)
return ofs > length
stack_almost_full._dont_insert_stackcheck_ = True
stack_almost_full._jit_look_inside_ = False
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