Re: [Bug-apl] cast from pointer to smaller type 'int'

[Juergen Sauermann]

Hi,

except that it did not compile on my machine:

*Thread_context.cc:73:44: error: invalid cast from type ‘pthread_t {aka 
long unsigned int}’ to type ‘uint64_t {aka long long unsigned int}’**
**        << reinterpret_cast<uint64_t>(thread)**
**                                            ^**
**make[1]: *** [apl-Thread_context.o] Error 1*

This is primarily because *pthread_t *is not a pointer on my box.

Best Regards,
/// Jürgen


On 09/20/2017 10:36 PM, Xiao-Yong Jin wrote:
> reinterpret_cast works from smaller sizes to larger sizes.
>
> So simply
>     reinterpret_cast<uint64_t *>(thread)
>
> should work for both of our machines (size_t is uint64_t for me).
>
> ... until some pthread implementation decides to hand you a larger sized struct 
> for pthread_t.
>     
> > On Sep 20, 2017, at 3:26 PM, Juergen Sauermann <address@hidden> wrote:
> >
> > Hi Xiao-Yong,
> >
> > I can compile this:
> >
> >         << reinterpret_cast<uint64_t>(
> >            reinterpret_cast<void *>(thread))
> >
> > Please let me know if it compiles on you box as well.
> >
> > Best Regards,
> > Jürgen
> >
> >
> > On 09/20/2017 10:00 PM, Juergen Sauermann wrote:
> > > Hi Xiao-Yong,
> > >
> > > with reinterpret_cast<size_t> I am getting (gcc 4.8)  this:
> > >
> > > Thread_context.cc: In member function ‘void 
> > > Thread_context::print(std::ostream&) const’:
> > > Thread_context.cc:73:42: error: invalid cast from type ‘pthread_t {aka long 
> > > unsigned int}’ to type ‘size_t {aka unsigned int}’
> > >          << reinterpret_cast<size_t>(thread)
> > >                                            ^
> > > make[1]: *** [apl-Thread_context.o] Error 1
> > >
> > > It seems a little ridiculous to me that replacing a good old C-style cast that 
> > > worked fine for the
> > > last 10 years cannot be replaced by one of the 3 members of the C++ zoo of 
> > > casts in a portable way?
> > >
> > > Maybe some intermediate cast to const void * can be done on your machine?
> > >
> > > Best Regards,
> > > Jürgen
> > >
> > >
> > > On 09/19/2017 11:44 PM, Xiao-Yong Jin wrote:
> > > > Should have got back to you sooner, but static_cast is not allowed between 
> > > > pointer types and non-pointer types.
> > > >
> > > > Thread_context.cc:73:11: error: static_cast from 'pthread_t' (aka 
> > > > '_opaque_pthread_t *') to 'int' is not allowed
> > > >         << static_cast<int>(thread)
> > > >            ^~~~~~~~~~~~~~~~~~~~~~~~
> > > >
> > > > I need reinterpret_cast<size_t> here.  I cannot reinterpret_cast<int> either, 
> > > > because of the difference in size.
> > > >
> > > >
> > > > > On Sep 11, 2017, at 3:01 PM, Juergen Sauermann <address@hidden>
> > > > >   wrote:
> > > > >
> > > > > Hi Xiao-Yong,
> > > > >
> > > > > I see. In this particular case the pthread_t is only used to identify a thread 
> > > > > and
> > > > > to distinguish it from other threads for debugging purposes. So as long as the
> > > > > compiler does not complain about the cast everything is fine. Cast to void * 
> > > > > instead of
> > > > > int would also be an option.
> > > > >
> > > > > /// Jürgen
> > > > >   
> > > > >
> > > > > On 09/11/2017 08:38 PM, Xiao-Yong Jin wrote:
> > > > >
> > > > > > I don't think there is a portable way of printing a variable of type pthread_t.  It 
> > > > > > could be a struct, depending on the implementation.  static_cast<int> is 
> > > > > > alright, but may not be useful in the future.
> > > > > >
> > > > > >
> > > > > >
> > > > > > > On Sep 11, 2017, at 1:08 PM, Juergen Sauermann <address@hidden>
> > > > > > >
> > > > > > >   wrote:
> > > > > > >
> > > > > > > Hi Xiao-Yong,
> > > > > > >
> > > > > > > thanks, maybe fixed in SVN 1011.
> > > > > > > Problem with that error is that the casted type is not a pointer, at least on 
> > > > > > > my machine.
> > > > > > >
> > > > > > > /// Jürgen
> > > > > > >
> > > > > > >
> > > > > > > On 09/11/2017 06:55 PM, Xiao-Yong Jin wrote:
> > > > > > >
> > > > > > >
> > > > > > > > At revision 1010
> > > > > > > >
> > > > > > > > Thread_context.cc:72:65: error: cast from pointer to smaller type 'int' loses 
> > > > > > > > information
> > > > > > > >     out << "thread #"     << setw(2) << N << ":" << setw(16)  << int(thread)