One test in data.cc crashes Octave 3.1.51

[Thomas Treichl]

John W. Eaton schrieb:
> On 14-Aug-2008, Thomas Treichl wrote:
> 
> | Thomas Treichl schrieb:
> | > John W. Eaton schrieb:
> | >> On 12-Aug-2008, Jaroslav Hajek wrote:
> | >>
> | >> To start with, run Octave under gdb and find out where it crashes.
> | > 
> | > I have some problems here, it looks to me like gdb on my i386 cannot debug PPC 
> | > code with the Rosetta backend (or at least I don't know how to do it). However, 
> | > I can see the wrong result (without a crash of Octave) with the i386 binary too. 
> | > If no other ideas then I'll have a look at that one and send my experiences as 
> | > soon as possible...
> | 
> | I have had a look at several Mac developer pages but it seems that it won't be 
> | possible to debug PPC on a 138 on 10.4. So I changed to the i386 binary and also 
> | have had a look at the Octave sources and I tried to find out more about this 
> | problem:
> | 
> | The strange thing is that none of the log2 and log10 results for complex numbers 
> | is correct (but log results seem to e correct). I've found the following code in 
> | ov-complex.cc which tells me (I hope that I read this correctly) that log and 
> | log10 are taken from libc++ and log2 is taken from Octave internals?
> | 
> |    COMPLEX_MAPPER (log, std::log)
> |    COMPLEX_MAPPER (log2, xlog2)
> |    COMPLEX_MAPPER (log10, std::log10)
> |    COMPLEX_MAPPER (log1p, ::log1p)
> 
> You can find the definitions of the xlog2 functions in
> liboctave/lo-mappers.cc.  They are:
> 
>   double
>   xlog2 (double x)
>   {
>   #if defined (HAVE_LOG2)
>     return log2 (x);
>   #else
>   #if defined (M_LN2)
>     static double ln2 = M_LN2;
>   #else
>     static double ln2 = log (2);
>   #endif
> 
>     return log (x) / ln2;
>   #endif
>   }
> 
>   Complex
>   xlog2 (const Complex& x)
>   {
>   #if defined (M_LN2)
>     static double ln2 = M_LN2;
>   #else
>     static double ln2 = log (2);
>   #endif
> 
>     return std::log (x) / ln2;
>   }
> 
> | Here is an example output of my Octave session:
> | 
> |    octave-3.1.51+:1> A = complex (0, Inf)
> |    A =    0 + Infi
> |    octave-3.1.51+:2> log (A)    ## correct
> |    ans = Inf + 1.571i
> |    octave-3.1.51+:3> log1p (A)  ## correct
> |    ans = Inf + 1.571i
> |    octave-3.1.51+:4> log2 (A)   ## should be Inf+2.266*i
> |    ans = Inf - NaNi
> |    octave-3.1.51+:5> log10 (A)  ## should be Inf+0.682*i
> |    ans = Inf - NaNi
> | 
> | Different number formats give me the same results:
> | 
> |    octave-3.1.51+:10> log10 (A) ## should be Inf+0.682*i
> |    ans = Inf - NaNi
> |    octave-3.1.51+:11> log10 (single (A))
> |    ans = Inf - NaNi
> | 
> | Hhmmm... Do I have a problem with 'cmath' and its libraries of the gcc 4.0.1 suite?
> 
> What do you see for the following program?
> 
>   #include <cmath>
>   #include <complex>
>   #include <iostream>
> 
>   int
>   main (void)
>   {
>     double inf = 1.0 / 0.0;
> 
>     double foo = std::log (std::complex<double> (0, inf)) / std::log (2);
> 
>     std::cout << foo << std::endl;
> 
>     return 0;
>   }
> 
> Here are the results on my system (AMD 64, Debian) using GCC 4.3.1:
> 
>   segfault:57> g++ foo.cc
>   segfault:58> ./a.out
>   (inf,nan)
>   segfault:59> g++ -O foo.cc
>   segfault:60> ./a.out
>   (inf,2.26618)

Thanks for the example program, I think we are getting closer. Now I can see (if 
I interpret this correctly) that the log function on my system cannot handle the 
complex type?! This would really be a bad thing

   ~/tmp $g++ --version
   i686-apple-darwin8-g++-4.0.1 (GCC) 4.0.1 (Apple Computer, Inc. build 5370)
   Copyright (C) 2005 Free Software Foundation, Inc.
   This is free software; see the source for copying conditions.  There is NO
   warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

   ~/tmp $ g++ foo.cc
   foo.cc: In function 'int main()':
   foo.cc:8: warning: division by zero in '1.0e+0 / 0.'
   foo.cc:10: error: cannot convert 'std::complex<double>' to 'double' in
   initialization
   ~/tmp $

The same if I try to make an executable PPC version

   ~/tmp $ g++ -arch ppc --version
   powerpc-apple-darwin8-g++-4.0.1 (GCC) 4.0.1 (Apple Computer, Inc. build 5370)
   Copyright (C) 2005 Free Software Foundation, Inc.
   This is free software; see the source for copying conditions.  There is NO
   warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

   ~/tmp $ g++ -arch ppc -isysroot /Developer/SDKs/MacOSX10.3.9.sdk -Wall foo.cc
   foo.cc: In function 'int main()':
   foo.cc:8: warning: division by zero in '1.0e+0 / 0.'
   foo.cc:10: error: cannot convert 'std::complex<double>' to 'double' in
   initialization
   ~/tmp $

Am I right?

   Thomas