[HDFS-10355] Fix thread_local related build issue on Mac OS X

• Type: Sub-task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: hdfs-client

Environment

OS: Mac OS X 10.11
clang: Apple LLVM version 7.0.2 (clang-700.1.81)

• Target Version/s: HDFS-8707
• Assignee: James Clampffer
• Reporter: Tibor Kiss
• Created: 02/May/16 13:35
• Updated: 26/Oct/18 12:58

Description

The native hdfs library uses C++11 features heavily.
One of such feature is thread_local storage class which is supported in GCC, Visual Studio and the community version of clang compiler, but not by Apple's clang (which is default on OS X boxes).
See further details here: http://stackoverflow.com/a/29929949

Even though not many Hadoop cluster runs on OS X developers still use this platform for development.

The problem can be solved multiple ways:
a) Stick to gcc/g++ or community based clang on OS X. Developers will need extra steps to build Hadoop.
b) Workaround thread_local with a helper class.
c) Get rid of all the globals marked with thread_local. Interface change will be erquired.
d) Disable multi threading support in the native client on OS X and document this limitation.

Compile error related to thread_local:

     [exec] /Users/tiborkiss/workspace/apache-hadoop/hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/lib/bindings/c/hdfs.cc:66:1: error: thread-local storage is not supported for the current target
     [exec] thread_local std::string errstr;
     [exec] ^
     [exec] /Users/tiborkiss/workspace/apache-hadoop/hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/lib/bindings/c/hdfs.cc:87:1: error: thread-local storage is not supported for the current target
     [exec] thread_local std::experimental::optional<fs_event_callback> fsEventCallback;
     [exec] ^
     [exec] /Users/tiborkiss/workspace/apache-hadoop/hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/lib/bindings/c/hdfs.cc:88:1: error: thread-local storage is not supported for the current target
     [exec] thread_local std::experimental::optional<file_event_callback> fileEventCallback;
     [exec] ^
     [exec] 1 warning and 3 errors generated.