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Date: Tue, 8 Aug 2017 15:36:00 +0000 (UTC)
From: "James Clampffer (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.13093186.1502203040000.118160.1502206560539@Atlassian.JIRA>
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References: <JIRA.13093186.1502203040000@Atlassian.JIRA> <JIRA.13093186.1502203040502@jira-lw-us.apache.org>
Subject: [jira] [Commented] (HDFS-12276) libhdfs++: uri parser has clang
 warnings that break external projects
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archived-at: Tue, 08 Aug 2017 15:36:07 -0000


    [ https://issues.apache.org/jira/browse/HDFS-12276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16118479#comment-16118479 ] 

James Clampffer commented on HDFS-12276:
----------------------------------------

Nice catch [~anatoli.shein].  It should be sufficient to just add a virtual destructor and define it in one of the .cc files to force a vtable to be instantiated in a single compilation unit.  The linker will generally be smart enough to fix this in the same way it can fold generated code for "inline" qualified functions together as an optimization pass but I don't know if clang does by default.

I think there's a couple ways to prevent, or at least deal with, these issues in the future:
-Find a covering set of all the warnings used by Hadoop related projects like orc, parquet, and arrow (and plenty of others).  Then use them in this library.  This is always going to be a step behind of anything being added to those libraries.
-You can always switch back to a more permissive build for third-party libs for other projects.  That's the approach we've taken with the things libhdfs++ depends on; this isn't really a bug in the library as much as it's a difference in how permissive the build should be.

> libhdfs++: uri parser has clang warnings that break external projects
> ---------------------------------------------------------------------
>
>                 Key: HDFS-12276
>                 URL: https://issues.apache.org/jira/browse/HDFS-12276
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs-client
>            Reporter: Anatoli Shein
>
> When trying to do a clang build of libhdfs++ as part of the ORC project I get some warnings that are treated as errors:
> In file included from /home/travis/build/apache/orc/c++/libs/libhdfspp/include/hdfspp/options.h:21:
> /home/travis/build/apache/orc/c++/libs/libhdfspp/include/hdfspp/uri.h:30:7: error: 'uri_parse_error' has no out-of-line virtual method definitions; its vtable will be emitted in every translation unit [-Werror,-Wweak-vtables]
> class uri_parse_error : public std::invalid_argument {
>       ^
> 2 errors generated.
> These should be fixed.


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