Re: [Boost-cmake] CMAKE_CXX_FLAGS on Darwin...

Subject: Re: [Boost-cmake] CMAKE_CXX_FLAGS on Darwin...
From: Sean Chittenden (sean_at_[hidden])
Date: 2009-10-30 18:11:09

> Adding the ${CMAKE_CXX_FLAGS} to ADD_DEFINITIONS() seems redundant.to
> me because CMAKE_CXX_FLAGS already sets definitions passed to the c++
> compiler. I think this flag is more useful for setting
> config-dependent flags, e.g. CMAKE_CXX_FLAGS_DEBUG and
> CMAKE_CXX_FLAGS_RELEASE, but maybe others on the list can correct me
> if I'm wrong.
>
> As I understand it, you should just be able to use ADD_DEFINITIONS(
> -gdwarf2 ) and then later ADD_DEFINITIONS( -Wno-deprecated ) later in
> the code snippet. If you want to use CMAKE_CXX_FLAGS instead, just set
> it like so: SET( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -gdwarf2 ).

For the code I'm working on, I have the following bootstrap steps:

1) sh autogen.sh # Calls cmake w/ platform specific flags and path  
information
2) cmake # CMakeLists.txt detects whether or not I need to build boost  
(eg: "if(EXISTS ${CONTRIBOBJ}/include/boost/asio.hpp)") and calls  
execute_script() to compile boost with project-specific parameters.   
CONTRIBOBJ is set to something like "obj/contrib-Darwin-i386".
3) I'm passing CMAKE_CXX_FLAGS to patch and contrib/boost/boosh.sh to  
build boost

I can confirm that I'm setting CMAKE_CXX_FLAGS:

CMAKE_CXX_FLAGS:  -gdwarf-2 -Wno-deprecated

via:

${CMAKE_COMMAND}
     -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} \
     -DCMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS} \
     -DCMAKE_IS_EXPERIMENTAL=YES_I_KNOW \     <<< Is this necessary  
any more?
     -DDCMAKE_VERBOSE_MAKEFILE=true \
[...]

And when I build boost: I'm not longer seeing either of those post  
1.40.0.  Starting with cmake2, it looks like CMAKE_CXX_FLAGS ceased  
working but I don't know how or why.  Is there a better way to pass  
CXX_FLAGS to boost?  -sc

cd /Users/sean/src/obj/contrib-Darwin-i386/boost-1.40.0.cmake4.obj/ 
libs/serialization/src && /opt/local/bin/g++-mp-4.3   - 
DBOOST_ALL_NO_LIB=1 -I/Users/sean/src/obj/contrib-Darwin-i386/ 
boost-1.40.0.cmake4     -O3 -DNDEBUG       -o CMakeFiles/ 
boost_serialization-mt-static.dir/basic_iserializer.cpp.o -c /Users/ 
sean/src/obj/contrib-Darwin-i386/boost-1.40.0.cmake4/libs/ 
serialization/src/basic_iserializer.cpp

?

PS Yes, I know I can get uname data in CMmake, but when I was first  
porting some code to cmake's build system it was easier to wrap cmake  
w/ a shell script and call uname than attempt to grok 100% of what  
cmake has to offer.  Slowly but surely I'm pushing various variables  
out of autogen.sh in to cmake files.

> On Thu, Oct 29, 2009 at 3:37 PM, Sean Chittenden  
> <sean_at_[hidden]> wrote:
>> I've been running with the following snippet in my boost build  
>> directory for
>> a while.
>>
>>> IF(CMAKE_COMPILER_IS_GNUCXX)
>>>  IF(APPLE)
>>>    ADD_DEFINITIONS(${CMAKE_CXX_FLAGS} "-gdwarf-2")
>>>  ENDIF(APPLE)
>>>
>>>  # At some point in the future, this won't be requied to silence an
>>>  # error message for boost, but for the time being it is.
>>>  ADD_DEFINITIONS(${CMAKE_CXX_FLAGS} "-Wno-deprecated")
>>> ENDIF(CMAKE_COMPILER_IS_GNUCXX)
>>>
>>
>> If boost isn't built for the current project, I have cmake call a  
>> shell
>> scipt to use cmake to build boost (passed in via
>> -DCMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS}).  The -gdwarf-2 flag prevents  
>> N_GSYM
>> errors on Darwin, similar to the following:
>>
>> cd
>> /Users/sean/src/obj/contrib-Darwin-i386/boost-1.40.0.cmake2.obj/ 
>> libs/thread/src
>> && /opt/local/bin/cmake -E cmake_link_script
>> CMakeFiles/boost_thread-mt-shared-debug.dir/link.txt --verbose=1
>> /opt/local/bin/g++-mp-4.3   -dynamiclib -headerpad_max_install_names
>>  -o ../../../lib/libboost_thread-mt-d.dylib -install_name
>> /Users/sean/src/obj/contrib-Darwin-i386/boost-1.40.0.cmake2.obj/lib/ 
>> libboost_thread-mt-d.dylib
>> CMakeFiles/boost_thread-mt-shared-debug.dir/pthread/thread.cpp.o
>> CMakeFiles/boost_thread-mt-shared-debug.dir/pthread/exceptions.cpp.o
>> CMakeFiles/boost_thread-mt-shared-debug.dir/pthread/once.cpp.o ld:  
>> warning:
>> can't find atom for N_GSYM stabs uninitialized_flag:G(0,1440) in
>> CMakeFiles/boost_thread-mt-shared-debug.dir/pthread/thread.cpp.old:  
>> warning:
>> can't find atom for N_GSYM stabs being_initialized:G(0,1440) in
>> CMakeFiles/boost_thread-mt-shared-debug.dir/pthread/thread.cpp.o
>> /opt/local/bin/cmake -E cmake_progress_report
>> /Users/sean/src/obj/contrib-Darwin-i386/boost-1.40.0.cmake2.obj/ 
>> CMakeFiles
>>  6
>>
>> Starting with cmake2, it looks like CMAKE_CXX_FLAGS is being reset  
>> somewhere
>> along the lines.  Is there a correct/better way to pass this in to  
>> CMake or
>> is there a way to have Boost cmake automatically set -gdwarf-2  
>> using the
>> above logic?  tia.  -sc

--
Sean Chittenden
sean_at_[hidden]