[jira] [Created] (HADOOP-11997) CMake CMAKE_C_FLAGS are non-portable

["Alan Burlison (JIRA)" <ji...@apache.org>]

Alan Burlison created HADOOP-11997:
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             Summary: CMake CMAKE_C_FLAGS are non-portable
                 Key: HADOOP-11997
                 URL: https://issues.apache.org/jira/browse/HADOOP-11997
             Project: Hadoop Common
          Issue Type: Sub-task
          Components: build
    Affects Versions: 2.7.0
         Environment: All
            Reporter: Alan Burlison
            Assignee: Alan Burlison
            Priority: Critical


hadoop-common-project/hadoop-common/src/CMakeLists.txt (https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/CMakeLists.txt#L110) contains the following unconditional assignments to CMAKE_C_FLAGS:

set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -g -Wall -O2")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -D_REENTRANT -D_GNU_SOURCE")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64")

There are several issues here:

1. "-D_GNU_SOURCE" globally enables the use of all Linux-only extensions in hadoop-common native source. This is probably a major contributor to the poor cross-platform portability of Hadoop native code to non-Linux platforms as it makes it easy for developers to use non-portable Linux features without realising. Use of Linux-specific features should be correctly bracketed with conditional macro blocks that provide an alternative for non-Linux platforms.

2. "-g -Wall -O2" turns on debugging for all builds, I believe the correct mechanism is to set the CMAKE_BUILD_TYPE CMake variable. If it is still necessary to override CFLAGS it should probably be done conditionally dependent on the value of CMAKE_BUILD_TYPE.

3. "-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64" On Solaris these flags are only needed for largefile support in ILP32 applications, LP64 applications are largefile by default. I believe the same is true on Linux, so these flags are harmless but redundant for 64-bit compilation.




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