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

[Jose Fonseca]

This was with GLIBC 2.21 in ubuntu 15.10:

$ ldd --version
ldd (Ubuntu GLIBC 2.21-0ubuntu4.1) 2.21

And it was with GCC 5.0.  I also tried GCC 4.9 but no difference.

And the funny thing is that I can't repro the nouveau build failure neither.

_Something_ causes these functions to be available on my system.  Not
sure exactly what.

I think we'll probably need to make a small test case for this, and run
`g++ -E` to get to the bottom of this.

And if nothing else, we might need to run this test case at configure.ac
time, to see when we need to do the `using std::isinf;`.


Jose



On 13/04/16 12:16, Pierre Moreau wrote:
> :-( I'll have another look this evening. Which version of glibc did it failed with?
> 
> (I saw your reply to the other patch, I'll dig deeper this evening.)
> 
> Thanks!
> Pierre
> 
>> On 13 Apr 2016, at 08:22, Jose Fonseca <jfonseca at vmware.com> wrote:
>>
>>> 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
>>
>