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fixing reader labels in core reader for non-trivial cycles

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Cycles like #0=(a #1=(#0#) #1#) with an inner cycle looping back to
an outer cycle would cause infinite loops.  We fix these by marking
objects as we patch reader labels, then clearing the marks.
This commit is contained in:
Alex Shinn 2015-07-11 21:06:28 +09:00
parent 76d088d260
commit 9959f90b7a
1 changed files with 8 additions and 5 deletions
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13
sexp.c
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@ -2594,17 +2594,18 @@ static int sexp_decode_utf8_char(const unsigned char* s) {
#endif
#if SEXP_USE_READER_LABELS
static sexp sexp_fill_reader_labels(sexp ctx, sexp x, sexp shares) {
static sexp sexp_fill_reader_labels(sexp ctx, sexp x, sexp shares, int state) {
sexp t, *p, *q;
if (sexp_reader_labelp(x))
return sexp_vector_data(shares)[sexp_unbox_reader_label(x)];
if (!x || !sexp_pointerp(x))
if (!x || !sexp_pointerp(x) || sexp_markedp(x) == state)
return x;
sexp_markedp(x) = state;
t = sexp_object_type(ctx, x);
p = (sexp*) (((char*)x) + sexp_type_field_base(t));
q = p + sexp_type_num_slots_of_object(t, x);
for ( ; p < q; ++p)
*p = sexp_fill_reader_labels(ctx, *p, shares);
*p = sexp_fill_reader_labels(ctx, *p, shares, state);
return x;
}
#endif
@ -3138,8 +3139,10 @@ sexp sexp_read_op (sexp ctx, sexp self, sexp_sint_t n, sexp in) {
else if (res == SEXP_RAWDOT)
res = sexp_read_error(ctx, "unexpected '.'", SEXP_NULL, in);
#if SEXP_USE_READER_LABELS
else if (!sexp_exceptionp(res) && sexp_vectorp(shares))
res = sexp_fill_reader_labels(ctx, res, shares);
else if (!sexp_exceptionp(res) && sexp_vectorp(shares)) {
res = sexp_fill_reader_labels(ctx, res, shares, 1); /* mark=1 */
res = sexp_fill_reader_labels(ctx, res, shares, 0); /* mark=0 */
}
#endif
sexp_maybe_unblock_port(ctx, in);
sexp_gc_release1(ctx);