GH-36388: [C++][Python] Return error from MakeArrayFromScalar on offset overflow

cpp/src/arrow/array/array_test.cc

@@ -767,6 +767,33 @@ TEST_F(TestArray, TestMakeArrayFromScalar) {
   }
 }
 
+TEST_F(TestArray, TestMakeArrayFromScalarOffsetOverflow) {
+  // Regression test for GH-36388: MakeArrayFromScalar should return an error
+  // when the total data size would overflow 32-bit offsets instead of silently
+  // producing an invalid array with negative offsets.
+
+  // A single-byte string repeated 2^31 times overflows int32 offsets
+  auto scalar = MakeScalar("x");
+  int64_t length = static_cast<int64_t>(1) << 31;
+  ASSERT_RAISES(Invalid, MakeArrayFromScalar(*scalar, length));
+
+  // A two-byte string repeated just over INT32_MAX/2 times also overflows
+  auto scalar2 = MakeScalar("xy");
+  int64_t length2 = (static_cast<int64_t>(1) << 30) + 1;
+  ASSERT_RAISES(Invalid, MakeArrayFromScalar(*scalar2, length2));
+
+  // Binary type has the same issue
+  auto bin_scalar = std::make_shared<BinaryScalar>(Buffer::FromString("abc"));
+  int64_t length3 = (static_cast<int64_t>(std::numeric_limits<int32_t>::max()) / 3) + 1;
+  ASSERT_RAISES(Invalid, MakeArrayFromScalar(*bin_scalar, length3));
+
+  // Large string type should NOT overflow (uses 64-bit offsets)
+  auto large_scalar = std::make_shared<LargeStringScalar>("x");
+  // Just verify it doesn't raise for a small count (we can't allocate 2^31 bytes here)
+  ASSERT_OK_AND_ASSIGN(auto arr, MakeArrayFromScalar(*large_scalar, 16));
+  ASSERT_EQ(arr->length(), 16);
+}
+
 TEST_F(TestArray, TestMakeArrayFromScalarSliced) {
   // Regression test for ARROW-13437
   auto scalars = GetScalars();

cpp/src/arrow/array/util.cc

@@ -853,6 +853,19 @@ class RepeatedArrayFactory {
 
   template <typename OffsetType>
   Status CreateOffsetsBuffer(OffsetType value_length, std::shared_ptr<Buffer>* out) {
+    // Check that the total data size does not overflow the offset type.
+    // For 32-bit offset types (e.g. StringType, BinaryType), value_length * length_
+    // must fit in int32_t, otherwise the offsets wrap around and produce an invalid
+    // array with negative offsets.
+    if (value_length > 0 && length_ > 0) {
+      int64_t total_size = static_cast<int64_t>(value_length) * length_;
+      if (total_size > static_cast<int64_t>(std::numeric_limits<OffsetType>::max())) {
+        return Status::Invalid(
+            "Cannot create array: total data size (", total_size,
+            " bytes) would overflow the offset type. Consider using a large_* "
+            "type (e.g. large_string, large_binary) for data exceeding 2 GB.");
+      }
+    }
     TypedBufferBuilder<OffsetType> builder(pool_);
     RETURN_NOT_OK(builder.Resize(length_ + 1));
     OffsetType offset = 0;

python/pyarrow/tests/test_array.py

@@ -442,6 +442,16 @@ def test_array_from_dictionary_scalar():
     assert result.equals(expected)
 
 
+def test_repeat_offset_overflow():
+    # GH-36388: pa.repeat should raise an error when the total data size
+    # would overflow 32-bit offsets, instead of returning an invalid array.
+    with pytest.raises(pa.ArrowInvalid, match="overflow"):
+        pa.repeat("x", 2**31)
+
+    with pytest.raises(pa.ArrowInvalid, match="overflow"):
+        pa.repeat("xy", 2**30 + 1)
+
+
 def test_array_getitem():
     arr = pa.array(range(10, 15))
     lst = arr.to_pylist()