Bug 98042

When building on Linux using clang++ and its standard library, libc++, the build fails with:

In file included from glsl/link_varyings.cpp:33:
In file included from ../../src/compiler/glsl/glsl_symbol_table.h:34:
In file included from ../../src/compiler/glsl/ir.h:33:
In file included from ../../src/compiler/glsl_types.h:29:
In file included from /usr/bin/../include/c++/v1/string.h:61:
/usr/include/string.h:518:12: error: exception specification in declaration does not match previous declaration
   virtual void visit(class ir_dereference_variable *) {}
                ^
extern int ffs (int __i) __THROW __attribute__ ((__const__));
           ^
../../src/util/bitscan.h:51:13: note: expanded from macro 'ffs'
#define ffs __builtin_ffs
            ^
../../src/util/bitscan.h:96:18: note: previous declaration is here
   const int i = ffs(*mask) - 1;
                 ^
../../src/util/bitscan.h:51:13: note: expanded from macro 'ffs'
#define ffs __builtin_ffs
            ^
../../src/compiler/glsl/ir_visitor.h:82:17: note: hidden overloaded virtual function 'ir_control_flow_visitor::visit' declared here: type mismatch at 1st parameter
      ('class ir_dereference_array *' vs 'ir_loop *')
In file included from glsl/link_varyings.cpp:33:
In file included from ../../src/compiler/glsl/glsl_symbol_table.h:34:
In file included from ../../src/compiler/glsl/ir.h:33:
In file included from ../../src/compiler/glsl_types.h:29:
In file included from /usr/bin/../include/c++/v1/string.h:61:
/usr/include/string.h:524:26: error: exception specification in declaration does not match previous declaration
__extension__ extern int ffsll (long long int __ll)
                         ^
../../src/util/bitscan.h:68:15: note: expanded from macro 'ffsll'
#define ffsll __builtin_ffsll
              ^
../../src/util/bitscan.h:104:18: note: previous declaration is here
   const int i = ffsll(*mask) - 1;
                 ^
../../src/util/bitscan.h:68:15: note: expanded from macro 'ffsll'
#define ffsll __builtin_ffsll


Build worked fine until recently. git bisect says the following:

ecd6fce2611e88ff8468a354cff8eda39f260a31 is the first bad commit
commit ecd6fce2611e88ff8468a354cff8eda39f260a31
Author: Rob Clark <robdclark@gmail.com>
Date:   Wed Aug 31 17:44:01 2016 -0400

    mesa/st: support lowering multi-planar YUV
    
    Support multi-planar YUV for external EGLImage's (currently just in the
    dma-buf import path) by lowering to multiple texture fetch's for each
    plane and CSC in shader.
    
    There was some discussion of alternative approaches for tracking the
    additional UV or U/V planes:
    
      https://lists.freedesktop.org/archives/mesa-dev/2016-September/127832.html
    
    They all seemed worse than pipe_resource::next
    
    Signed-off-by: Rob Clark <robdclark@gmail.com>

:040000 040000 80840dcad2d468df7741746515b03247c41a1084 88f03e54885c7b5b1090fb09709e7daf66972941 M	src