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https://issues.apache.org/jira/browse/HADOOP-11997?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14560753#comment-14560753
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Alan Burlison commented on HADOOP-11997:
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I've currently modified the various CMake files to set RelWithDebInfo if no
build mode is specified, I'll remove that and just set CFLAGS explicitly if
that's considered to be a better option.
However the -D_GNU_SOURCE flag is toxic to portability and will just repeatedly
cause portability breakage if it's left in so I'm intending to remove it and
explicitly bracket all such Linux-specific code in the source with
#define/#undef blocks. That will mean that people doing port work to other
platforms will have an easier time of it in future.
Adding Solaris Studio compiler support is a long-term goal but initially just
targeting gcc is the simplest option so I'm proposing just to add Solaris/gcc
support initially. Note also that Solaris Studio is also available on Linux
(http://www.oracle.com/technetwork/server-storage/solarisstudio/downloads/index-jsp-141149.html)
so when Studio support is added it needs to be done separately from the
platform detection in any case.
> 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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