[Debian-astro-maintainers] Bug#787725: Bug#787725: gyoto: FTBFS on 32-bit systems (assumes size_t is unsigned long)

[Thibaut Paumard]

Le 04/06/2015 15:33, Aaron M. Ucko a écrit :

> I would suggest (unconditionally) extending Gyoto::Property with
> get_size_t and and set_size_t methods, and redefining
> GYOTO_PROPERTY_SIZE_T accordingly.
> 
> Could you please take a look?


Dear Aaron,

Unconditionally, this will not work, at least the way Property is
supposed to work: on 64-bit arches, the compiler will not be able to
distinguish the two distinct constructors for unsigned long and size_t
because it really is the same. Besides, I'd rather not break the ABI
already.

I could extend Property with new typedefs, accessors and constructors
for size_t only for the architectures that need it, but I don't know how
to determine this automatically.

There is a solution that appears to be working but relies on undefined
behaviour. I can also extend the test suite to make sure it actually
does the right thing (I've tested manually under i386 already). Do you
see a real-world case in which this will fail:

/// Define a Property of type Long
#define GYOTO_PROPERTY_SIZE_T(class, name, fname)      \
  Gyoto::Property                                              \
  (#name,                                                      \
   reinterpret_cast<Gyoto::Property::set_unsigned_long_t>((void
(Object::*)(size_t val))&class::fname), \
   reinterpret_cast<Gyoto::Property::get_unsigned_long_t>((size_t
(Object::* )() const)&class::fname)),

Kind regards, Thibaut.

-- 
* Dr Thibaut Paumard       | LESIA/CNRS - Table équatoriale (bât. 5)   *
* Tel: +33 1 45 07 78 60   | Observatoire de Paris - Section de Meudon *
* Fax: +33 1 45 07 79 17   | 5, Place Jules Janssen                    *
* thibaut.paumard at obspm.fr | 92195 MEUDON CEDEX (France)               *

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