[Insight-developers] [Vxl-users] Compiling with gcc and c++0x

[Williams, Norman K]

I have a patch that adds '-Werror=gnu' if CLang++ is the C++ compiler.
This gets rid of all the inline static float initializer errors, but it
also makes necessary a slight change in vnl_lsqr.cxx because CLang defines
__GNUC__, and -Werror=gnu makes all the GNU extensions throw an error.


I don't know if there's any place in ITK besides VXL that uses Gnu
extensions; the places that VXL uses them seem to me to be of dubious and
limited utility, and stink up the source code with #ifdefs.  But that's
just one man's opinion.

On 1/2/12 12:13 PM, "Brad King" <brad.king at kitware.com> wrote:

>On 12/29/2011 11:43 AM, David Doria wrote:
>> On Thu, Dec 29, 2011 at 9:38 AM, Amitha Perera <amitha at thepereras.org>
>>wrote:
>>> The choice to use or not use the inline float initialization is based
>>>on a
>>> try-compile
>>
>> I am using the VXL that ships with ITK. I started from scratch (fresh
>> build directory), this time just trying to build ITK itself with the
>> -std=gnu++0x flag, and got the same errors.
>
>The try-compile correctly rejects the option for me:
>
>$ mkdir ITK-build && cd ITK-build
>$ export CXX=g++ CXXFLAGS=-std=gnu++0x
>$ cmake ../ITK -DITK_BUILD_ALL_MODULES=OFF -DBUILD_EXAMPLES=OFF \
>               -DITKGroup_Core=OFF -DModule_ITKVNL=ON
>...
>-- Enabled ITKVNL, requested by Module_ITKVNL.
>...
>-- Performing Test VCL_STATIC_CONST_INIT_FLOAT
>-- Performing Test VCL_STATIC_CONST_INIT_FLOAT - Failed
>...
>$ cat CMakeFiles/CMakeError.log
>...
>Performing Test VCL_STATIC_CONST_INIT_FLOAT failed with the following
>output:
>/usr/bin/g++ -std=gnu++0x ... -DVCL_STATIC_CONST_INIT_FLOAT ... -c
>.../vxl_platform_tests.cxx
>.../vxl_platform_tests.cxx:266:26: error: 'constexpr' needed for in-class
>initialization of static data member 'x' of non-integral type
>.../vxl_platform_tests.cxx:267:27: error: 'constexpr' needed for in-class
>initialization of static data member 'y' of non-integral type
>.../vxl_platform_tests.cxx: In function 'int main()':
>.../vxl_platform_tests.cxx:270:21: error: 'x' is not a member of 'A'
>.../vxl_platform_tests.cxx:270:38: error: 'y' is not a member of 'A'
>...
>$ cat Modules/ThirdParty/VNL/src/vxl/vcl/vcl_config_compiler.h
>...
>//#define VCL_CAN_STATIC_CONST_INIT_FLOAT 1 /* allowed */
>//#define VCL_CAN_STATIC_CONST_INIT_FLOAT 0 /* not allowed */
>#ifndef VCL_CAN_STATIC_CONST_INIT_FLOAT
># define VCL_CAN_STATIC_CONST_INIT_FLOAT 0
>#endif
>...
>$ make
>...works...
>
>-Brad
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