Re: [Vxl-maintainers] Compilation with clang (xcode 4.0.2)

[Sean M. <se...@ro...>]

On Mon, 23 May 2011 12:46:40 -0400, Brad King said:

>> 2. vnl_test_all cannot be linked because of missing symbols (see
>> output below).  It turned out the static const variables are declared
>> and initialized in the header, but not **defined**.  My understanding
>> of C++ 98 standard 9.4.2/2 is if these variables are used in places
>> other than integral expression, they need to be defined.  If I remove
>> the "#if !VCL_STATIC_CONST_INIT_INT_NO_DEFN" guards in
>> core/vnl/vnl_numeric_traits.cxx, the related linking errors went away.
>> 
>> Well, two things I want to check with the community.  First, is my
>> understanding of the standard correct?
>
>Yes, IIRC.
>
>> Second, even if it is, I recall the VCL_STATIC_CONST_INIT_* macros
>> had been introduced mostly to fix broken compilers.  Any suggestions
>> on how shall we proceed?
>
>I think Sean McBride (CCed) has built vnl with Clang inside ITK.
>Sean, did you see/fix any problems like this in ITK's vnl?

Sorry for the delay, it was a holiday here yesterday.

I submit nightly dashboards of both ITK and vxl, both built using clang,
but not the clang from Xcode 4, but rather a build from a recent svn
revision.  I update it every few weeks.  They both build these days, but
did not at first.

Regarding #2, though clang is right to warn/error, such code is very
common and _is_ conformant as of C++0x.  As such, IIRC, the clang folks
changed it from error to warning at some point.  I believe clang also
defaults to C++03, and so this warning is on, but if you specify C++0x,
then you should get no warning.

I guess, strictly speaking, vxl either needs to change, or require C+
+0x.  But in practice, most compilers seems to be forgiving enough.

-- 
____________________________________________________________
Sean McBride, B. Eng                 se...@ro...
Rogue Research                        www.rogue-research.com 
Mac Software Developer              Montréal, Québec, Canada