Re: Bugs blocking the 6.1 release

[Markus Mützel]

Am 16. Mai 2020 um 16:38 Uhr schrieb "John W. Eaton":
> On 5/16/20 4:58 AM, "Markus Mützel" wrote:
> > Thanks for the quick fix. I could successfully create the tarball with that 
> > change (hg id 178d101fd37d).
> > 
> > Cross-building the stable-octave target with MXE Octave fails with the 
> > following error:
> > 
> > /home/osboxes/Documents/Repositories/Octave/mxe-octave-stable/tmp-stable-octave/octave-6.0.1/libinterp/octave-value/ov-fcn-handle.cc:
> >  In constructor 'octave::simple_fcn_handle::simple_fcn_handle(const 
> > octave_value&, const string&)':
> > /home/osboxes/Documents/Repositories/Octave/mxe-octave-stable/tmp-stable-octave/octave-6.0.1/libinterp/octave-value/ov-fcn-handle.cc:181:28:
> >  warning: declaration of 'octave_function* fcn' shadows a parameter 
> > [-Wshadow]
> >    181 |           octave_function *fcn = m_fcn.function_value ();
> >        |                            ^~~
> 
> [...]
> 
> I'll check out the warnings.  What version of GCC are you using that 
> produces these warnings?  I don't recall seeing them with GCC 8.
> 
> > /home/osboxes/Documents/Repositories/Octave/mxe-octave-stable/tmp-stable-octave/octave-6.0.1/libinterp/octave-value/ov-fcn-handle.cc:
> >  In member function 'virtual bool 
> > octave_fcn_handle::load_hdf5(octave_hdf5_id, const char*)':
> > /home/osboxes/Documents/Repositories/Octave/mxe-octave-stable/tmp-stable-octave/octave-6.0.1/libinterp/octave-value/ov-fcn-handle.cc:2640:27:
> >  error: cannot bind non-const lvalue reference of type 'octave_hdf5_id&' 
> > {aka 'long long int&'} to an rvalue of type 'octave_hdf5_id' {aka 'long 
> > long int'}
> >   2640 |       if (afh->load_hdf5 (group_hid, space_hid, type_hid))
> >        |                           ^~~~~~~~~
> > /home/osboxes/Documents/Repositories/Octave/mxe-octave-stable/tmp-stable-octave/octave-6.0.1/libinterp/octave-value/ov-fcn-handle.cc:2022:57:
> >  note:   initializing argument 1 of 'bool 
> > octave::anonymous_fcn_handle::load_hdf5(octave_hdf5_id&, octave_hdf5_id&, 
> > octave_hdf5_id&)'
> >   2022 |   bool anonymous_fcn_handle::load_hdf5 (octave_hdf5_id& group_hid,
> >        |                                         ~~~~~~~~~~~~~~~~^~~~~~~~~
> > make[5]: *** [Makefile:20696: 
> > libinterp/octave-value/liboctave_value_la-ov-fcn-handle.lo] Error 1
> > 
> > 
> > Some of those are warnings that I also see for native builds on Ubuntu 
> > Linux. But the error about the non-const lvalue seems to be Windows 
> > specific. I'm not sure why gcc doesn't mind on Linux though (maybe some 
> > standard extension?).
> 
> Yeah, strange.  I'll try a Windows build and see if I can understand why 
> that's failing.

I think I finally understand why this is failing:
For native compilations on my Linux box, hid_t is typedef'ed as int64_t. In the 
version of the HDF5 headers that is included in MXE Octave, hid_t is typedef'ed 
as int. Like shown in the error message, octave_hdf5_id is likely typedef'ed as 
int64_t.
Thus, the types match for native builds on Linux. For Windows MXE builds, the 
compiler tries to create a temporary rvalue of matching type to call load_hdf5 
and fails on binding the non-const lvalue reference to the temporary rvalue.
To be honest, the error message would have been a lot more helpful if it 
mentioned the type of hid_t...

I used the attached changes to fix that error and to also avoid the shadowed 
variable warnings.

I'll report back when the cross-compilation has finished and I could test the 
performance on Windows.

Markus

ov-fcn-handle_cross_compile.patch
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