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https://issues.apache.org/jira/browse/IMPALA-9781?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17121367#comment-17121367
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ASF subversion and git services commented on IMPALA-9781:
---------------------------------------------------------
Commit b1883405cd59988b92df2799656666ff2f733c0e in impala's branch
refs/heads/master from Joe McDonnell
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=b188340 ]
Reapply IMPALA-9781: Fix GCC 7 unaligned 128-bit loads / stores
When running a release binary built with GCC 7.5.0, it crashes
with an unaligned memory error in multiple pieces of code.
In these locations, we are doing stores to 128-bit values, but we
cannot guarantee alignment. GCC 7 must be optimizing the code to
use instructions that require a higher level of alignment than
we can provide.
This switches the code locations to use memcpy to avoid the
unaligned stores (with local variables as necessary).
Testing:
- Ran exhaustive tests with a release binary built by GCC 7.5.0
- Ran UBSAN core tests
- Add unaligned test case in decimal-test
Change-Id: I7edd8beeb15e4fbb69126a9f97a1476a4b8f12a9
Reviewed-on: http://gerrit.cloudera.org:8080/16009
Tested-by: Impala Public Jenkins <[email protected]>
Reviewed-by: Tim Armstrong <[email protected]>
> Fix GCC 7 runtime issue: Unaligned loads and stores for int128_t types
> ----------------------------------------------------------------------
>
> Key: IMPALA-9781
> URL: https://issues.apache.org/jira/browse/IMPALA-9781
> Project: IMPALA
> Issue Type: Bug
> Components: Backend
> Affects Versions: Impala 4.0
> Reporter: Joe McDonnell
> Assignee: Joe McDonnell
> Priority: Major
> Fix For: Impala 4.0
>
>
> When running with a release binary built with GCC 7, Impala crashes with
> multiple distinct unaligned memory errors. They are all related to
> manipulating 128-bit values. Presumably GCC 7 added an optimization to use an
> instruction that requires alignment for setting 128-bit values. The locations
> impacted are:
> SlotRef::GetDecimalValInterpreted():
>
> {code:java}
> case 16:
> return
> DecimalVal(*reinterpret_cast<int128_t*>(t->GetSlot(slot_offset_)));
> {code}
> DecimalUtil::DecodeFromFixedLenByteArray():
>
>
> {code:java}
> template<typename T>
> static inline void DecodeFromFixedLenByteArray(
> const uint8_t* buffer, int fixed_len_size, T* v) {
> ...
> *v = 0; <--- unaligned store
> {code}
> DictDecoder::GetValue():
> {code:java}
> virtual void GetValue(int index, void* buffer) {
> T* val_ptr = reinterpret_cast<T*>(buffer);
> ...
> *val_ptr = dict_[index]; <--- unaligned store
> }
> {code}
> These can be converted to use memcpy / memset to avoid the unaligned
> stores/loads.
>
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