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https://issues.apache.org/jira/browse/HDFS-9265?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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James Clampffer updated HDFS-9265:
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Attachment: HDFS-9265.HDFS-8707.000.patch
Simple fix. As far as I can tell it won't cause any cycles.
Now the block reader will only have one shared_ptr referencing it instead of a
shared_ptr and unique_ptr fighting over who'd call the destructor first.
> Use of undefined behavior in remote_block_reader causing deterministic
> crashes.
> -------------------------------------------------------------------------------
>
> Key: HDFS-9265
> URL: https://issues.apache.org/jira/browse/HDFS-9265
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs-client
> Reporter: James Clampffer
> Assignee: James Clampffer
> Priority: Blocker
> Attachments: HDFS-9265.HDFS-8707.000.patch
>
>
> The remote block reader relies on undefined behavior in how it uses
> enable_shared_from_this.
> http://en.cppreference.com/w/cpp/memory/enable_shared_from_this
> The spec states a shared_ptr to an object inheriting from
> enable_shared_from_this must be live before calling make_shared_from_this.
> Calling make_shared_from_this without an existing shared_ptr is undefined
> behavior and causes deterministic crashes when the code is built with GCC.
> example:
> class foo : public enable_shared_from_this {/*bar*/};
> safe:
> auto ptr1 = std::make_shared<foo>();
> auto ptr2 = foo->make_shared_from_this();
> broken:
> foo *ptr = new foo();
> auto ptr2 = foo->make_shared_from_this(); //no existing live shared_ptr
> In order to fix the input stream should call std::make_shared and hang onto a
> shared_ptr to the block reader. The block reader will then be free to call
> make_shared_from this as much as it wants without issue.
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