Merge PR #292: Fix overflow bug in DividePrim

smarr · Aug 5, 2019 · eb16019 · eb16019
2 parents d3985a8 + cea6675
commit eb16019
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Showing 2 changed files with 18 additions and 1 deletion.
diff --git a/core-lib/TestSuite/IntegerTests.ns b/core-lib/TestSuite/IntegerTests.ns
@@ -195,6 +195,11 @@ class IntegerTests usingPlatform: platform testFramework: minitest = (
 
       self assert:  3 equals: 7 / 2.0.
       self assert:  2 equals: 7 / 3.5.
+
+      self assert: 9223372036854775808 equals: (* Java.MIN_VALUE *)   -9223372036854775808 / -1.
+
+      (* To trigger issue, we need to compute the value, because it is otherwise parsed as a big integer *)
+      self assert: 9223372036854775808 equals: (* Java.MIN_VALUE *) ((-922337203685477580 * 10) - 8) / -1.
     )
 
     public testDouble = (

diff --git a/src/som/primitives/arithmetic/DividePrim.java b/src/som/primitives/arithmetic/DividePrim.java
@@ -12,11 +12,19 @@
 @GenerateNodeFactory
 @Primitive(primitive = "int:divideBy:", selector = "/")
 public abstract class DividePrim extends ArithmeticPrim {
-  @Specialization
+  private static final BigInteger OVERFLOW_RESULT =
+      BigInteger.valueOf(Long.MIN_VALUE).divide(BigInteger.valueOf(-1));
+
+  @Specialization(guards = "!isOverflowDivision(left, right)")
   public final long doLong(final long left, final long right) {
     return left / right;
   }
 
+  @Specialization(guards = "isOverflowDivision(left, right)")
+  public final Object doLongWithOverflow(final long left, final long right) {
+    return OVERFLOW_RESULT;
+  }
+
   @Specialization
   @TruffleBoundary
   public final Object doBigInteger(final BigInteger left, final BigInteger right) {
@@ -40,4 +48,8 @@ public final Object doLong(final long left, final BigInteger right) {
   public final Object doLong(final long left, final double right) {
     return (long) (left / right);
   }
+
+  protected static final boolean isOverflowDivision(final long left, final long right) {
+    return left == Long.MIN_VALUE && right == -1;
+  }
 }