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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