Benjamin Kietzman created ARROW-4186:
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Summary: [C++] BitmapWriters clobber the first byte when length=0
Key: ARROW-4186
URL: https://issues.apache.org/jira/browse/ARROW-4186
Project: Apache Arrow
Issue Type: Bug
Components: C++
Reporter: Benjamin Kietzman
Assignee: Antoine Pitrou
When a BitmapWriter or FirstTimeBitmapWriter is constructed with length=0 then
Finish() is invoked, the byte at {{start_offset / 8}} is zeroed
The following change causes the test to fail:
{code}
--- a/cpp/src/arrow/util/bit-util-test.cc
+++ b/cpp/src/arrow/util/bit-util-test.cc
@@ -274,6 +274,10 @@ TEST(FirstTimeBitmapWriter, NormalOperation) {
auto writer = internal::FirstTimeBitmapWriter(bitmap, 10, 3);
WriteVectorToWriter(writer, {0, 0, 0});
}
+ {
+ auto writer = internal::FirstTimeBitmapWriter(bitmap, 13, 0);
+ WriteVectorToWriter(writer, {});
+ }
{
auto writer = internal::FirstTimeBitmapWriter(bitmap, 13, 3);
WriteVectorToWriter(writer, {1, 0, 1});
{code}
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