[Mesa-dev] [PATCH v2] math: Import isinf and others to global namespace

[Jose Fonseca]

On 01/04/16 13:18, Pierre Moreau wrote:
> On 01:11 PM - Apr 01 2016, Jose Fonseca wrote:
>> On 31/03/16 23:08, Pierre Moreau wrote:
>>> Starting from C++11, several math functions, like isinf, moved into the std
>>> namespace. Since cmath undefines those functions before redefining them inside
>>> the namespace, and glibc 2.23 defines the C variants as macros, the C variants
>>> in global namespace are not accessible any longer.
>>>
>>> v2: Move the fix outside of Nouveau, as suggested by Jose Fonseca, since anyone
>>>      might need it when GCC switches to C++14 by default with GCC 6.0.
>>>
>>> Signed-off-by: Pierre Moreau <pierre.morrow at free.fr>
>>> ---
>>>   include/cpp11_math.h                | 61 +++++++++++++++++++++++++++++++++++++
>>>   src/gallium/auxiliary/util/u_math.h |  3 ++
>>>   2 files changed, 64 insertions(+)
>>>   create mode 100644 include/cpp11_math.h
>>>
>>> diff --git a/include/cpp11_math.h b/include/cpp11_math.h
>>> new file mode 100644
>>> index 0000000..1f4aa3c
>>> --- /dev/null
>>> +++ b/include/cpp11_math.h
>>
>> I'm not sure a new header is necessary for this.
>>
>> What this is doing is making C++11 math functions "appear" like C99 ones.
>> It's not making things matching C++11 standard.
>>
>> So IMO the right place for this is the end of c99_math.h
>
> I was planning to put it in the c99 header first, but as I was including some
> C++ header, I felt that having a separate header which would only be included
> by C++ files would be better. I could have the `#ifdef __cplusplus` around the
> whole block inside the c99_math.h instead, if you prefer it that way.
>
> Thanks,
> Pierre
>

I moved this to c99_math.h and was about to commit, but this causes 
build failures with gcc 5.0:

   $ scons
   [...]
In file included from src/gallium/auxiliary/util/u_math.h:44:0,
                  from src/mesa/main/macros.h:35,
                  from src/compiler/glsl/lower_vec_index_to_swizzle.cpp:36:
include/c99_math.h:198:12: error: ‘constexpr bool std::isinf(double)’ 
conflicts with a previous declaration
  using std::isinf;
             ^
In file included from /usr/include/features.h:364:0,
                  from /usr/include/stdio.h:27,
                  from src/compiler/glsl/ir.h:29,
                  from src/compiler/glsl/lower_vec_index_to_swizzle.cpp:32:
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:201:1: note: previous 
declaration ‘int isinf(double)’
  __MATHDECL_1 (int,isinf,, (_Mdouble_ __value)) __attribute__ 
((__const__));
  ^




It looks like newer GLIBC already does this somehow..  I'm not sure 
what's the exact trigger.


I wonder if the problem can be avoided by including math.h at the top:


diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp 
b/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
index 500ab89..e61f59e7 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
@@ -20,6 +20,7 @@
   * OTHER DEALINGS IN THE SOFTWARE.
   */

+#include <math.h>
  #include "codegen/nv50_ir.h"
  #include "codegen/nv50_ir_target.h"






Jose