Re: Compilation failure, template problems

[Jaroslav Hajek]

On Sat, Nov 14, 2009 at 4:31 PM, Michael Goffioul <address@hidden> wrote:

Hi,

Using recent octave archive, MSVC fails to compile liboctave due
to a template problems. The error is the following:

../../liboctave/CNDArray.cc(763) : error C2563: mismatch in formal
parameter list
../../liboctave/CNDArray.cc(763) : error C2563: mismatch in formal
parameter list
../../liboctave/CNDArray.cc(763) : error C2440: 'specialization' :
cannot convert from 'overloaded-function' to 'double (__cdecl *const
)(Complex)'
       None of the functions with this name in scope match the target type
../../liboctave/CNDArray.cc(763) : error C2973: 'do_mx_unary_map' :
invalid template argument 'overloaded-function'
       c:\sources\playground\c\octave-graphics-hg\liboctave\mx-inlines.cc(264)
: see declaration of 'do_mx_unary_map'
../../liboctave/CNDArray.cc(763) : error C2668: 'do_mx_unary_map' :
ambiguous call to overloaded function
       c:\sources\playground\c\octave-graphics-hg\liboctave\mx-inlines.cc(271):
could be 'RNDA do_mx_unary_map<NDArray,ComplexNDArray,double
std::abs<double>(const std::complex<double> &)>(const XNDA &)'
       with
       [
           RNDA=NDArray,
           XNDA=ComplexNDArray
       ]
       c:\sources\playground\c\octave-graphics-hg\liboctave\mx-inlines.cc(264):
or       'RNDA do_mx_unary_map<NDArray,ComplexNDArray,& abs>(const
XNDA &)'
       with
       [
           RNDA=NDArray,
           XNDA=ComplexNDArray
       ]
       while trying to match the argument list '(const ComplexNDArray)'

Any idea how to work around the problem? This part of the code seems
pretty recent.

Michael.

I think this should compile - name resolution for template function parameters works like for regular parameters. Here the signature is fully determined by the previous parameters, so a unique match should be found.
So I think this is a bug in MSVC.
Unfortunately, the typical way to pick a specific overload (cast the name reference to specific function pointer type) doesn't work in this case, because only integral and enum casts are allowed in template params. Maybe just specifying std::abs<double> instead of std::abs would work? Otherwise, I think you'll need to wrap std::abs in a function with unique name and substitute that for the template parameter.


-- 
RNDr. Jaroslav Hajek
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz