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fix another space-safety issue in interpreter loop

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When the main interpreter loop is called for an application where the
argument array coincides with the current runstack pointer, then the
protocol is that the callee gets to modify that space --- and it
should modify that space as arguments become unused. The interpreter
was always copying arguments to a fresh space, though.
This commit is contained in:
Matthew Flatt 2016-12-14 16:28:28 -07:00
parent f2be44dea4
commit 4683b023ab
1 changed files with 25 additions and 7 deletions
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32
racket/src/racket/src/eval.c
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@ -2655,7 +2655,7 @@ scheme_do_eval(Scheme_Object *obj, int num_rands, Scheme_Object **rands,
Scheme_Object *v;
GC_CAN_IGNORE Scheme_Object *tmpv; /* safe-for-space relies on GC_CAN_IGNORE */
GC_CAN_IGNORE Scheme_Object **tmprands; /* safe-for-space relies on GC_CAN_IGNORE */
GC_MAYBE_IGNORE_INTERIOR Scheme_Object **old_runstack;
GC_MAYBE_IGNORE_INTERIOR Scheme_Object **old_runstack, **runstack_base;
GC_MAYBE_IGNORE_INTERIOR MZ_MARK_STACK_TYPE old_cont_mark_stack;
#if USE_LOCAL_RUNSTACK
GC_MAYBE_IGNORE_INTERIOR Scheme_Object **runstack;
@ -2721,6 +2721,17 @@ scheme_do_eval(Scheme_Object *obj, int num_rands, Scheme_Object **rands,
MZ_CONT_MARK_POS += 2;
old_runstack = RUNSTACK;
if (num_rands >= 0) {
/* If we have a call with arguments at runstack, then we're
allowed to recycle the argument part of the runstack. In fact,
space safety may relies on reusing that space to clear argument
values. */
if (rands == RUNSTACK)
runstack_base = RUNSTACK + num_rands;
else
runstack_base = RUNSTACK;
} else
runstack_base = RUNSTACK;
old_cont_mark_stack = MZ_CONT_MARK_STACK;
if (num_rands >= 0) {
@ -2803,7 +2814,7 @@ scheme_do_eval(Scheme_Object *obj, int num_rands, Scheme_Object **rands,
data = SCHEME_CLOSURE_CODE(obj);
if ((RUNSTACK - RUNSTACK_START) < data->max_let_depth) {
if ((runstack_base - RUNSTACK_START) < data->max_let_depth) {
rands = evacuate_runstack(num_rands, rands, RUNSTACK);
if (rands == p->tail_buffer) {
@ -2842,7 +2853,7 @@ scheme_do_eval(Scheme_Object *obj, int num_rands, Scheme_Object **rands,
n = num_params - has_rest;
RUNSTACK = old_runstack - num_params;
RUNSTACK = runstack_base - num_params;
CHECK_RUNSTACK(p, RUNSTACK);
RUNSTACK_CHANGED();
@ -2903,7 +2914,7 @@ scheme_do_eval(Scheme_Object *obj, int num_rands, Scheme_Object **rands,
return NULL; /* Doesn't get here */
}
stack = RUNSTACK = old_runstack - num_params;
stack = RUNSTACK = runstack_base - num_params;
CHECK_RUNSTACK(p, RUNSTACK);
RUNSTACK_CHANGED();
@ -2927,7 +2938,7 @@ scheme_do_eval(Scheme_Object *obj, int num_rands, Scheme_Object **rands,
return NULL; /* Doesn't get here */
}
}
RUNSTACK = old_runstack;
RUNSTACK = runstack_base;
RUNSTACK_CHANGED();
}
@ -3169,7 +3180,7 @@ scheme_do_eval(Scheme_Object *obj, int num_rands, Scheme_Object **rands,
rands = p->ku.apply.tail_rands;
p->ku.apply.tail_rator = NULL;
p->ku.apply.tail_rands = NULL;
RUNSTACK = old_runstack;
RUNSTACK = runstack_base;
RUNSTACK_CHANGED();
} else {
break;
@ -3943,7 +3954,7 @@ scheme_do_eval(Scheme_Object *obj, int num_rands, Scheme_Object **rands,
rands = p->ku.apply.tail_rands;
p->ku.apply.tail_rator = NULL;
p->ku.apply.tail_rands = NULL;
RUNSTACK = old_runstack;
RUNSTACK = runstack_base;
RUNSTACK_CHANGED();
goto apply_top;
}
@ -3967,6 +3978,13 @@ scheme_do_eval(Scheme_Object *obj, int num_rands, Scheme_Object **rands,
returnv_never_multi:
/* If resetting RUNSTACK to old_runstack makes the stack larger, we
need to clear extra slots to avoid making an old value on the
runstack suddenly live again */
while ((uintptr_t)RUNSTACK > (uintptr_t)old_runstack) {
RUNSTACK--;
*RUNSTACK = NULL;
}
MZ_RUNSTACK = old_runstack;
MZ_CONT_MARK_STACK = old_cont_mark_stack;
MZ_CONT_MARK_POS -= 2;