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Fix edgecase segfault of BigDecimal#remainder #349

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Merged
tompng merged 1 commit into from
Jun 10, 2025
+13 −7
Merged

Fix edgecase segfault of BigDecimal#remainder #349

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14 changes: 7 additions & 7 deletions ext/bigdecimal/bigdecimal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2043,14 +2043,14 @@ BigDecimal_divremain(VALUE self, VALUE r, Real **dv, Real **rv)
b = GetVpValue(r, 0);
}

if (!b) return DoSomeOne(self, r, rb_intern("remainder"));
if (!b) return Qfalse;
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@tompng tompng Jun 10, 2025

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I don't think using Qfalse and Qtrue instead of false and true, but this pattern is frequently used in bigdecimal.c even if the function name starts with BigDecimal_.
But this pattern is used in is_zero, is_one and BigDecimal_DoDivmod.
I think it's better to refactor in a separate pull request

SAVE(b);

if (VpIsPosInf(b) || VpIsNegInf(b)) {
GUARD_OBJ(*dv, NewZeroWrapLimited(1, 1));
VpSetZero(*dv, 1);
*rv = a;
return Qnil;
return Qtrue;
}

mx = (a->MaxPrec + b->MaxPrec) *VpBaseFig();
Expand All @@ -2074,7 +2074,7 @@ BigDecimal_divremain(VALUE self, VALUE r, Real **dv, Real **rv)

*dv = d;
*rv = ff;
return Qnil;
return Qtrue;
}

/* call-seq:
Expand All @@ -2087,11 +2087,11 @@ BigDecimal_divremain(VALUE self, VALUE r, Real **dv, Real **rv)
static VALUE
BigDecimal_remainder(VALUE self, VALUE r) /* remainder */
{
VALUE f;
Real *d, *rv = 0;
f = BigDecimal_divremain(self, r, &d, &rv);
if (!NIL_P(f)) return f;
return VpCheckGetValue(rv);
if (BigDecimal_divremain(self, r, &d, &rv)) {
return VpCheckGetValue(rv);
}
return DoSomeOne(self, r, rb_intern("remainder"));
Comment on lines +2091 to +2094
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@tompng tompng Jun 10, 2025

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Same interface as BigDecimal_DoDivmod

        if (BigDecimal_DoDivmod(self, b, &div, &mod)) {
            return BigDecimal_to_i(VpCheckGetValue(div));
        }
        return DoSomeOne(self, b, rb_intern("div"));

}

/* call-seq:
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6 changes: 6 additions & 0 deletions test/bigdecimal/test_bigdecimal.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -1089,6 +1089,12 @@ def test_remainder_with_rational
assert_kind_of(BigDecimal, BigDecimal("3").remainder(1.quo(3)))
end

def test_remainder_coerce
o = Object.new
def o.coerce(x); [x, BigDecimal("3")]; end
assert_equal(BigDecimal("1.1"), BigDecimal("7.1").remainder(o))
end

def test_divmod
x = BigDecimal((2**100).to_s)
assert_equal([(x / 3).floor, 1], x.divmod(3))
Expand Down