On 11/01/2016 15:26, Brad King wrote:
What is adding -m64 to CMAKE_STATIC_LINKER_FLAGS? That value is indeed
meant to be used to pass flags to "ar" because CMake (for historical
reasons) abuses the term "linker" to refer to the archiver used for a
static library.
That's been added by in a CMakeLists.txt via an include of a common
cmake script for setting up the per-platform compilation flags.
https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/HadoopCommon.cmake
elseif(CMAKE_SYSTEM_NAME STREQUAL "SunOS")
# Solaris flags. 64-bit compilation is mandatory, and is checked
earlier.
hadoop_add_compiler_flags("-m64 -D__EXTENSIONS__
-D_POSIX_PTHREAD_SEMANTICS -D_XOPEN_SOURCE=500")
hadoop_add_linker_flags("-m64")
which calls:
# Add flags to all the CMake compiler variables
macro(hadoop_add_compiler_flags FLAGS)
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${FLAGS}")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${FLAGS}")
endmacro()
# Add flags to all the CMake linker variables
macro(hadoop_add_linker_flags FLAGS)
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${FLAGS}")
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} ${FLAGS}")
set(CMAKE_STATIC_LINKER_FLAGS "${CMAKE_STATIC_LINKER_FLAGS} ${FLAGS}")
endmacro()
So is the answer here to add -m64 just to CMAKE_EXE_LINKER_FLAGS and
CMAKE_SHARED_LINKER_FLAGS and not to CMAKE_STATIC_LINKER_FLAGS? Are
CMAKE_STATIC_LINKER_FLAGS only ever used with ar?
But I'm struggling to understand when passing in linker flags to ar
*ever* makes sense, at least on *nix platforms.
The name "LINK_FLAGS" is used as a placeholder there to share the
implementation with similar substitutions done in actual link line
generation. See above about the naming.
The question here is what changed between 2.8.6 and 3.3.2 that causes
-m64 to start showing up in CMAKE_STATIC_LINKER_FLAGS.
Yes indeed, if I'd been able to figure that out I think I'd have been
able to figure out how to change the CMake macros to get round the problem.
It's not the only problem I have hit with CMake's Solaris support, see
for example
https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/HadoopCommon.cmake#L194
# CMAKE_SYSTEM_PROCESSOR is set to the output of 'uname -p', which on
Solaris is
# the 'lowest' ISA supported, i.e. 'i386' or 'sparc'. However in order
for the
# standard CMake modules to look in the right places it needs to reflect
the required
# compilation mode, i.e. 64 bit. We therefore force it to either 'amd64'
or 'sparcv9'.
There seems to be an assumption baked into CMake that if the underlying
OS is *nix and is 32-bit then all executables that run on it are 32 bit
and if it is 64-bit then all the executables are 64-bit as well, so
looking at 'uname -p' is sufficient to determine the type of executables
that should be produced. Unfortunately that's not correct for either
Solaris or Linux.
Thanks,
--
Alan Burlison
--
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