Re: ‘pi’ shadows a global declaration

[John W. Eaton]

On 07/09/2017 11:30 PM, Dmitri A. Sergatskov wrote:
> Probably no a big problem. Mostly fyi:

> ../src/liboctave/numeric/lo-specfun.cc:3460:19: warning: declaration of
> ‘pi’ shadows a global declaration [-Wshadow] const float pi =
> 3.14159265358979323846f; ^~
> ../src/liboctave/numeric/lo-specfun.cc:3198:25: note: shadowed
> declaration is here static const double pi = 3.14159265358979323846; ^~

Yeah, I noticed that.  We currently use a mixture of these kinds of 
locally defined constants and macros like M_PI that may be defined by 
math.h.  Since we generally want to avoid macros from C-language headers 
in C++ code we try to only use C++ headers instead of C headers (<cmath> 
instead of <math.h>) but we also define _GNU_SOURCE, which currently 
causes macros like M_PI to be defined, at least on some systems.

So we could just use the macros, but I'm not sure that we should depend 
on them as they are not standard for C++ code.  Maybe we should define 
our own header file for math constants and use them consistently?

Whatever we do, I'd prefer to use the same constants in all Octave code.

jwe