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new a788c42 ARROW-13600: [C++] Fix maybe uninitialized warnings
a788c42 is described below
commit a788c42d44a8c22b2bb271e8d7de795e93abb3ef
Author: Keith Kraus <[email protected]>
AuthorDate: Mon Aug 16 01:50:36 2021 +0000
ARROW-13600: [C++] Fix maybe uninitialized warnings
cc @michalursa to double check the changes in the hashing as that's a
pretty performance sensitive chunk of code if I understand correctly
Closes #10907 from kkraus14/fix_maybe_uninitialized
Authored-by: Keith Kraus <[email protected]>
Signed-off-by: Yibo Cai <[email protected]>
---
cpp/src/arrow/compute/exec/key_hash.cc | 9 ++++++++-
cpp/src/arrow/tensor.cc | 2 +-
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/cpp/src/arrow/compute/exec/key_hash.cc
b/cpp/src/arrow/compute/exec/key_hash.cc
index 081411e..dcc42ed 100644
--- a/cpp/src/arrow/compute/exec/key_hash.cc
+++ b/cpp/src/arrow/compute/exec/key_hash.cc
@@ -198,8 +198,15 @@ void Hashing::hash_varlen_helper(uint32_t length, const
uint8_t* key, uint32_t*
last_stripe[1] = last_stripe_base[1];
last_stripe[1] &= mask;
}
+
+ // The stack allocation and memcpy here should be optimized out by the
compiler.
+ // Using a reinterpret_cast causes a compiler warning on gcc and can lead
to incorrect
+ // results. See https://issues.apache.org/jira/browse/ARROW-13600 for more
info.
+ uint32_t lanes[4];
+ memcpy(&lanes, &last_stripe, sizeof(last_stripe));
+
for (int j = 0; j < 4; ++j) {
- uint32_t lane = reinterpret_cast<const uint32_t*>(last_stripe)[j];
+ uint32_t lane = lanes[j];
acc[j] += (lane * PRIME32_2);
acc[j] = ROTL(acc[j], 13);
acc[j] *= PRIME32_1;
diff --git a/cpp/src/arrow/tensor.cc b/cpp/src/arrow/tensor.cc
index d591bac..30ae8c4 100644
--- a/cpp/src/arrow/tensor.cc
+++ b/cpp/src/arrow/tensor.cc
@@ -328,7 +328,7 @@ struct NonZeroCounter {
}
const Tensor& tensor_;
- int64_t result;
+ int64_t result = 0;
};
} // namespace
