[IMPALA-6039] BitReader::GetAligned() doesn't zero out trailing bytes

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: Impala 2.11.0
• Fix Version/s: Impala 2.11.0
• Component/s: Backend
• Target Version: Product Backlog
• Epic Color: ghx-label-1
• Assignee: Tim Armstrong
• Reporter: Tim Armstrong
• Created: 11/Oct/17 01:02
• Updated: 16/Nov/17 21:26
• Resolved: 16/Nov/17 21:26

Description

BitReader::GetAligned() only sets the initial bytes of the output value, leaving the remaining bytes set to whatever they were previously. It isn't clear if this is intentional and undocumented or a latent bug.

The problem is non-obvious because the current callsites either call it with a single byte at a time (GetVlqInt()), or initialize the output value to zero and always call GetAligned() with the same num_bytes value (RleDecoder).