Hi Gehua and Sean,
First of all, thanks for Gehua's help. Does Gehua's method fix your issue, Sean? I notice there are two submissions from Rogue Research and both of them are error-free. So I wonder whether there is difference between checkouted source code and exported source code. If Gehua's method works, do you think it's necessary to submit a patch to vxl repository for this issue? 
Lianqing Yu

Date: Fri, 8 Jun 2012 16:56:05 -0400
Subject: Re: [Vxl-maintainers] [Vxl-users] VXL 1.17.0 Release Candicate 2 is available
From: yanggehua@gmail.com
To: sean@rogue-research.com
CC: yulq@live.cn; vxl-maintainers@lists.sourceforge.net; vxl-users@lists.sourceforge.net

I also had the same warnings with clang in the past.  The way I resolved it was to add "-Werror=gnu"  to the c++ compiler flags **and** set VXL_UPDATE_CONFIGURATION to true following by re-running cmake.  With this flag, the try-compile test will fail and set VCL_CAN_STATIC_CONST_INIT_FLOAT to 0, which eliminates all of these warnings. 

Gehua Yang.

On Fri, Jun 8, 2012 at 3:38 PM, Sean McBride <sean@rogue-research.com> wrote:
On Wed, 6 Jun 2012 00:42:51 +0800, YULianqing said:

>Dear all, I'm glad to introduce the second release candidate (RC2) of
>VXL 1.17.0 for you to test. The main change to RC2 compared to RC1 is
>the inclusion of dcrispell's fix to remove cyclic dependency issue in
>the case of shared libary build. Please feel free to give me comments
>and suggestions.

So I downloaded and tried to use cmake to do an out-of-source build.  After I 'configure', with default options, it gives an error: "bvpl_octree using pthreads".  That's not a very helpful message...  What does it mean?

Nevertheless, I proceeded to 'generate' and compile (with clang).

I get a million warnings like this:

warning: in-class initializer for static data member of type 'const double' is a GNU extension