[Octave-bug-tracker] [bug #42583] log2() returns inaccurate result for many integer powers of 2, unlike Matlab

[Kai Torben Ohlhus]

Follow-up Comment #13, bug #42583 (project octave):

The past changes resulted in a compilation error ('log2' is not a member of
'gnulib') for my Debian Jessie with GCC 4.9:

../liboctave/numeric/lo-mappers.cc:95:10: error: 'log2' is not a member of
'gnulib'
   return gnulib::log2 (x);
          ^
../liboctave/numeric/lo-mappers.cc:95:10: note: suggested alternative:
In file included from /usr/include/features.h:374:0,
                 from /usr/include/stdint.h:25,
                 from /usr/lib/gcc/x86_64-linux-gnu/4.9/include/stdint.h:9,
                 from ../oct-conf-post.h:167,
                 from ../config.h:3372,
                 from /
../liboctave/numeric/lo-mappers.cc:25:
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:144:1: note:   'log2'
 __MATHCALL (log2,, (_Mdouble_ __x));
 ^
../liboctave/numeric/lo-mappers.cc: In function 'float xlog2(float)':
../liboctave/numeric/lo-mappers.cc:310:10: error: 'log2f' is not a member of
'gnulib'
   return gnulib::log2f (x);
          ^
../liboctave/numeric/lo-mappers.cc:310:10: note: suggested alternative:
In file included from ../libgnu/math.h:27:0,
                 from /usr/include/c++/4.9/cmath:44,
                 from /usr/include/c++/4.9/complex:44,
                 from ../liboctave/util/oct-cmplx.h:27,
                 from ../liboctave/numeric/lo-mappers.h:29,
                 from ../liboctave/numeric/lo-mappers.cc:32:
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:144:1: note:   'log2f'
 __MATHCALL (log2,, (_Mdouble_ __x));
 ^

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