[GRASS-dev] g.region -g crashes in a latlon location

[Yann Chemin]

wow...
ok then we have to get to GDAL dev list about that...?
Yann

2008/7/22 Glynn Clements <glynn at gclements.plus.com>:
>
> Yann Chemin wrote:
>
>> This is on my system:
>
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x00007fda5b45ca7e in sincos () from /usr/lib/libgdal1.5.0.so.1
>
> Whoah; GDAL?
>
> sincos() is defined in libm:
>
>       void sincos(double x, double *sin, double *cos);
>
> But gdal has its own version in frmts/hdf4/hdf-eos/GDapi.c (GDapi.c?
> That was in Maciej's report):
>
> #if !defined(HP9000) && !defined(DEC_ALPHA)
> void
> sincos(double val, double *sin_val, double *cos_val)
> {
>    *sin_val = sin(val);
>    *cos_val = cos(val);
>    return;
> }
> #endif
>
> On my system, nearly all of the symbols in libm are weak, so
> definitions in other libraries can override them, even for use within
> libm.
>
> I note that G_set_geodesic_distance_lat2() computes both sin() and
> cos() for two angles:
>
>    stm = sin(tm);
>    ctm = cos(tm);
>    sdtm = sin(dtm);
>    cdtm = cos(dtm);
>
> That could explain why it only happens with optimisation enabled: the
> compiler notices that it needs both sin() and cos() of the same angle,
> and uses sincos() instead.
>
> Similarly, if GDAL was compiled with optimisation, GDAL's sincos()
> calculates both sin() and cos() of its argument (well that's the whole
> point of the function), so the compiler optimises GDAL's sincos() to
> sincos(), resulting in infinite reecursion.
>
> I'm fairly sure that's what is going on here.
>
> I think that the ultimate solution would be for GDAL to be a bit more
> careful about defining sincos, i.e. have configure actually check
> whether libm defines sincos() rather than assuming that it only exists
> on specific platforms.
>
> --
> Glynn Clements <glynn at gclements.plus.com>
>



-- 
Yann Chemin
International Rice Research Institute
Office: http://www.irri.org/gis
Perso: http://www.freewebs.com/ychemin