Re: Cast ambiguity compilation error

[Jaroslav Hajek]

On Sun, Jan 18, 2009 at 9:56 PM, Daniel J Sebald <address@hidden> wrote:
> I've gotten Mercurial working on my FC3 machine (hoorah!).  Python path
> problem...
>
> Compiling the latest source on this older system has uncovered one small
> syntax problem, I believe.  Or I have some outdated compiler, std library
> headers, or something.
>
> The issue is the abiguity of '!' operator overloaded in oct-inttypes.h.  An
> example string of errors is below.  There are only a few spots where these
> errors are occuring.  (Note that the errors are happening when building
> liboctave, not the src.)  I fixed one instance with a kludge old-style case:
>
>
> diff -Pur octave/liboctave/intNDArray.cc octave-mod/liboctave/intNDArray.cc
> --- octave/liboctave/intNDArray.cc      2009-01-18 13:45:08.000000000 -0600
> +++ octave-mod/liboctave/intNDArray.cc  2009-01-18 13:53:19.000000000 -0600
> @@ -53,7 +53,7 @@
>    {
>      T val = this->elem (i);
>
> -      if (((double)val) != 0.0 && ((double)val) != 1.0)
> +      if (val != 0.0 && val != 1.0)
>        return true;
>    }
>
>
> Things then compiled along until hitting another instance:
>
> oct-inttypes.h: In function `bool operator!=(const double&, const
> octave_int<T>&) [with T = int64_t]':
> mx-s-i64nda.cc:11:   instantiated from here
> oct-inttypes.h:1059: error: call of overloaded `mop(const double&, int64_t)'
> is ambiguous
> oct-inttypes.h:193: note: candidates are: static bool
> octave_int_cmp_op::mop(T, double) [with xop = octave_int_cmp_op::ne, T =
> double]
> oct-inttypes.h:198: note:                 static bool
> octave_int_cmp_op::mop(double, T) [with xop = octave_int_cmp_op::ne, T =
> long long int]
> oct-inttypes.h:211: note:                 static bool
> octave_int_cmp_op::mop(double, uint64_t) [with xop = octave_int_cmp_op::ne]
> oct-inttypes.h:212: note:                 static bool
> octave_int_cmp_op::mop(double, int64_t) [with xop = octave_int_cmp_op::ne]
> oct-inttypes.h:213: note:                 static bool
> octave_int_cmp_op::mop(int64_t, double) [with xop = octave_int_cmp_op::ne]
> oct-inttypes.h:214: note:                 static bool
> octave_int_cmp_op::mop(uint64_t, double) [with xop = octave_int_cmp_op::ne]
>
> which is much more difficult for me to kludge because it is embedded in some
> definition strings.
>
I guess you have gcc 3 series, right? (Judging by the FC3). The answer
is yes, it is a compiler defect.
The mop overloads inside octave_int_cmp_op are unambiguous and
standard conforming.
For more info, see this previous discussion:
http://www.nabble.com/error-when-compiling-Octave-in-Cygwin-td20966037.html#a20966037
and this one on comp.lang.c++:
http://groups.google.com/group/comp.lang.c++/browse_thread/thread/398e6ba0047f902a/c258528a9b0258b9?lnk=gst&q=ambiguous+overload

Your best solution is to upgrade to gcc 4 (and I suggest upgrading the
FC3 anyway). I'm fairly reluctant to alter the conforming code to
please an obsolete compiler due to a particular defect (and so far
nobody even asked for it).
Even if that is an old machine, there should be up-to-dat GNU/Linux
distros fit for it.
But even if you don't want to upgrade the distro, you can build g++ 4
for yourself.
cheers



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