[Impala-ASF-CR] IMPALA-5031: Remove undefined behavior "reference binding to null"

["Jim Apple (Code Review)" <ge...@cloudera.org>]

Hello Tim Armstrong, Dan Hecht,

I'd like you to reexamine a change.  Please visit

    http://gerrit.cloudera.org:8080/7008

to look at the new patch set (#4).

Change subject: IMPALA-5031: Remove undefined behavior "reference binding to null"
......................................................................

IMPALA-5031: Remove undefined behavior "reference binding to null"

When p has type T* and p is nullptr, then T x = p[0] has undefined
behavior (obviously). Less obviously, T& x = p[0] also has undefined
behavior -- references cannot be null. That undefined behavior can be
caused by expressions like &v[0] when v is a vector of size 0. The
issue is that the expression is parsed as &(v[0]), aka
&(v.operator[](0)). The return type of the operator[] method is T&,
and when v is empty the return value is a null reference.

This was recognized by the C++ standards committe and fixed in
Committee Draft 2008. See LWG Defect Report 464:

http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#464

This patch was created by running the following command, then fixing
the resulting compile errors:

    find be/src -type f -execdir \
      sed -i 's/&\([A-Za-z0-9_]\+\)\[0\]/\1.data()/g' \{\} \;

Change-Id: Ifef5c3de686318bff4eac7dfad6e1639ddadb8f2
---
M be/src/exec/aggregation-node.cc
M be/src/exec/data-source-scan-node.cc
M be/src/exec/delimited-text-parser-test.cc
M be/src/exec/hash-join-node-ir.cc
M be/src/exec/hash-join-node.cc
M be/src/exec/hash-table.cc
M be/src/exec/hbase-scan-node.cc
M be/src/exec/hdfs-parquet-scanner-ir.cc
M be/src/exec/hdfs-parquet-scanner.cc
M be/src/exec/hdfs-rcfile-scanner.cc
M be/src/exec/hdfs-scan-node-base.h
M be/src/exec/hdfs-scanner.h
M be/src/exec/hdfs-sequence-scanner.cc
M be/src/exec/hdfs-sequence-table-writer.cc
M be/src/exec/hdfs-text-scanner.cc
M be/src/exec/kudu-scanner.cc
M be/src/exec/nested-loop-join-node.cc
M be/src/exec/old-hash-table-ir.cc
M be/src/exec/old-hash-table.cc
M be/src/exec/parquet-column-stats.inline.h
M be/src/exec/partitioned-aggregation-node-ir.cc
M be/src/exec/partitioned-aggregation-node.cc
M be/src/exec/partitioned-hash-join-node-ir.cc
M be/src/exec/partitioned-hash-join-node.cc
M be/src/exec/select-node.cc
M be/src/exec/unnest-node.cc
M be/src/experiments/tuple-splitter-test.cc
M be/src/exprs/expr-context.cc
M be/src/exprs/expr-test.cc
M be/src/exprs/expr-value.h
M be/src/exprs/string-functions-ir.cc
M be/src/rpc/authentication.cc
M be/src/rpc/thrift-util-test.cc
M be/src/runtime/bufferpool/buffer-pool-test.cc
M be/src/runtime/disk-io-mgr-test.cc
M be/src/runtime/parallel-executor-test.cc
M be/src/runtime/row-batch-serialize-test.cc
M be/src/runtime/tmp-file-mgr-test.cc
M be/src/udf/udf-test-harness.h
M be/src/util/bitmap.h
M be/src/util/coding-util-test.cc
M be/src/util/coding-util.cc
M be/src/util/dict-encoding.h
M be/src/util/runtime-profile.cc
M be/src/util/streaming-sampler.h
M be/src/util/tuple-row-compare.h
M be/src/util/uid-util.h
M be/src/util/webserver.cc
48 files changed, 113 insertions(+), 109 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/08/7008/4
-- 
To view, visit http://gerrit.cloudera.org:8080/7008
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Ifef5c3de686318bff4eac7dfad6e1639ddadb8f2
Gerrit-PatchSet: 4
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Jim Apple <jb...@apache.org>
Gerrit-Reviewer: Dan Hecht <dh...@cloudera.com>
Gerrit-Reviewer: Lars Volker <lv...@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <ta...@cloudera.com>