Dimitri Vorona created ARROW-2790:
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Summary: [C++] Buffers contain uninitialized memory
Key: ARROW-2790
URL: https://issues.apache.org/jira/browse/ARROW-2790
Project: Apache Arrow
Issue Type: New Feature
Components: C++
Affects Versions: 0.9.0
Reporter: Dimitri Vorona
Hi,
currently, buffers can contain uninitalized memory when built with buffer
builders. This happens in two ways:
# The most common implementation of AppendNull(s) adds a null-bit to the
null-map and increments the lengths, leaving chunks of data values untouched
# The padding is never initialized
This can lead to a number of problems, some of more or less theoretical nature,
but it's worth fixing just to make valgrind happy again and allow it to run in
CI :) Also, leaking uninitialized memory over a wire is never nice, and
currently problem 1. ist never mitigated by the ipc writers (although the
problem 2 ist).
This PR changes the behaviour of AppendNull(s) for the affected builders and
adds a lot of checks to ensure the correct initialization. Most of the test
succeed the current master, but cause valgrind warnings, if the buffer builders
aren't patched.
I decided not to test explicitly if the nulled/padded memory is really 0, just
that it can be read without errors, since the specs don't specify exact values.
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