[petsc-dev] complex fix and -Wfloat-equal

[Lisandro Dalcin]

On Thu, 30 Jan 2020 at 08:25, Smith, Barry F. <bsmith at mcs.anl.gov> wrote:

>
>
> > On Jan 27, 2020, at 3:42 PM, Lisandro Dalcin <dalcinl at gmail.com> wrote:
> >
> > +#if defined(__GNUC__) && (__GNUC__ >= 4)
> > +#pragma GCC system_header
> > +#endif
> > +
> >  #define PETSC_CXX_COMPLEX_FIX(Type) \
> >  static inline PetscComplex operator+(const PetscComplex& lhs, const
> Type& rhs) { return const_cast<PetscComplex&>(lhs) + PetscReal(rhs); } \
> >  static inline PetscComplex operator+(const Type& lhs, const
> PetscComplex& rhs) { return PetscReal(lhs) +
> const_cast<PetscComplex&>(rhs); } \
> >
> > Would that be an acceptable solution o we should rather implement a
> configure test and define PETSC_HAVE_PRAGMA_GCC_SYSTEM_HEADER ?
>
>   I'm fine with having it handled by the version check.
>
>
Thanks.

>
> > These are the kind of errors that show up for EVERY C++ source compile
> if -Wfloat-equal is passed.
> >
> > /home/devel/petsc/dev/include/petsccxxcomplexfix.h: In function ‘bool
> operator==(const PetscComplex&, const PetscInt&)’:
> > /home/devel/petsc/dev/include/petsccxxcomplexfix.h:47:134: warning:
> comparing floating point with == or != is unsafe [-Wfloat-equal]
> >    47 | static inline bool operator==(const PetscComplex& lhs, const
> Type& rhs) { return const_cast<PetscComplex&>(lhs).imag() == PetscReal(0)
> && const_cast<PetscComplex&>(lhs).real() == PetscReal(rhs); } \
> >       |
>                                                                     ^
> > /home/devel/petsc/dev/include/petsccxxcomplexfix.h:60:1: note: in
> expansion of macro ‘PETSC_CXX_COMPLEX_FIX’
> >    60 | PETSC_CXX_COMPLEX_FIX(PetscInt)
>
>   I don't understand the above. Are these two unrelated issues? Or does
> adding the first chunk of code prevent the warnings from the second chunk
> of code.
>
>
Yes, that's it. using `#pragma GCC system_header`  suppresses all warnings
in that header file, including of course `-Wfloat-equal`.



-- 
Lisandro Dalcin
============
Research Scientist
Extreme Computing Research Center (ECRC)
King Abdullah University of Science and Technology (KAUST)
http://ecrc.kaust.edu.sa/
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