Fix x.fix and x.frac affected by prec limit, Stop -x and x.abs round with prec limit (#409)

Author: tompng

ext/bigdecimal/bigdecimal.c

@@ -1702,8 +1702,8 @@ static VALUE
 BigDecimal_neg(VALUE self)
 {
     BDVALUE a = GetBDValueMust(self);
-    BDVALUE c = NewZeroWrapLimited(1, a.real->Prec * BASE_FIG);
-    VpAsgn(c.real, a.real, -1);
+    BDVALUE c = NewZeroWrapNolimit(1, a.real->Prec * BASE_FIG);
+    VpAsgn(c.real, a.real, -10);
     RB_GC_GUARD(a.bigdecimal);
     return CheckGetValue(c);
 }
@@ -2176,8 +2176,8 @@ static VALUE
 BigDecimal_abs(VALUE self)
 {
     BDVALUE a = GetBDValueMust(self);
-    BDVALUE c = NewZeroWrapLimited(1, a.real->Prec * BASE_FIG);
-    VpAsgn(c.real, a.real, 1);
+    BDVALUE c = NewZeroWrapNolimit(1, a.real->Prec * BASE_FIG);
+    VpAsgn(c.real, a.real, 10);
     VpChangeSign(c.real, 1);
     RB_GC_GUARD(a.bigdecimal);
     return CheckGetValue(c);
@@ -2215,7 +2215,7 @@ static VALUE
 BigDecimal_fix(VALUE self)
 {
     BDVALUE a = GetBDValueMust(self);
-    BDVALUE c = NewZeroWrapLimited(1, (a.real->Prec + 1) * BASE_FIG);
+    BDVALUE c = NewZeroWrapNolimit(1, (a.real->Prec + 1) * BASE_FIG);
     VpActiveRound(c.real, a.real, VP_ROUND_DOWN, 0); /* 0: round off */
     RB_GC_GUARD(a.bigdecimal);
     return CheckGetValue(c);
@@ -2359,7 +2359,7 @@ static VALUE
 BigDecimal_frac(VALUE self)
 {
     BDVALUE a = GetBDValueMust(self);
-    BDVALUE c = NewZeroWrapLimited(1, (a.real->Prec + 1) * BASE_FIG);
+    BDVALUE c = NewZeroWrapNolimit(1, (a.real->Prec + 1) * BASE_FIG);
     VpFrac(c.real, a.real);
     RB_GC_GUARD(a.bigdecimal);
     return CheckGetValue(c);

test/bigdecimal/test_bigdecimal.rb

@@ -2051,6 +2051,31 @@ def test_div_mod_rem_operation_with_limit
     end
   end
 
+  def test_sign_operator_ignores_limit
+    plus_x = BigDecimal('7' * 100)
+    minus_x = -plus_x
+    BigDecimal.save_limit do
+      BigDecimal.limit(3)
+      assert_equal(plus_x, +plus_x)
+      assert_equal(minus_x, +minus_x)
+      assert_equal(minus_x, -plus_x)
+      assert_equal(plus_x, -minus_x)
+      assert_equal(plus_x, minus_x.abs)
+      assert_equal(plus_x, plus_x.abs)
+    end
+  end
+
+  def test_fix_frac_ignores_limit
+    fix = BigDecimal("#{'4' * 56}")
+    frac = BigDecimal("0.#{'7' * 89}")
+    x = fix + frac
+    BigDecimal.save_limit do
+      BigDecimal.limit(3)
+      assert_equal(fix, x.fix)
+      assert_equal(frac, x.frac)
+    end
+  end
+
   def test_sign
     BigDecimal.mode(BigDecimal::EXCEPTION_OVERFLOW, false)
     BigDecimal.mode(BigDecimal::EXCEPTION_NaN, false)