Re: [Patch, fortran, 4.9] Use bool type instead gfc_try

["N.M. Maclaren" <nmm1 at cam dot ac dot uk>]

On Mar 21 2013, Joseph S. Myers wrote:
> > > 
> > > > now that the Fortran frontend is C++ we can use the primitive bool
> > > > type instead of inventing our own.
> > > 
> > > Well, C99's "bool" (_Bool) was already used before. ...
> >
> > Er, that is making a serious mistake or, at least, running the risk of
> > one.  C++'s bool and C99's _Bool are NOT compatible types.  The UK tried
> > to get _Bool either made compatible with C++ or (preferably) dropped, but
> > failed in both.
>
> They have been ABI-compatible in GCC ever since I implemented C99 _Bool 
> ....

That is another matter entirely.  The code of gcc/gfortran is supposed
to be compilable with other compilers, and it is foolish to make
unnecessary assumptions by relying on undefined behaviour.

The simple facts are that C++ does NOT define bool to be compatible with
_Bool, and there are enough differences in specification and semantics
to make it likely that they are not the same in at least some compilers.
This mess has caused and still causes no end of problems for Fortran
interoperability and in standards like MPI.


Regards,
Nick Maclaren.