[Gdal-dev] Assertion in .tab driver

[Daniel]

If he got a crash it could very well  be the same problem since
isspace expects input that can be represented as an unsigned char or
EOF.

Looking at Microsofts documentation for isspace at:
http://msdn2.microsoft.com/en-us/library/y13z34da(VS.80).aspx

"When used with a debug CRT library, isspace will display a CRT assert
if passed a parameter that is not EOF or in the range of 0 through
0xFF. When used with a non-debug CRT library, isspace will use the
parameter as an index into an array, with undefined results if the
parameter is not EOF or in the range of 0 through 0xFF."

So this could very well cause a crash. I don't think that the correct
solution is to use iswspace since the rest of the code can't handle
wide chars anyway.

Some locales might even have characters >127 that should be treated as
whitespace and changing to use iswspace won't fix that.

This seems to be quite a common problem, see "C Language Gotchas"
http://www.greenend.org.uk/rjk/2001/02/cfu.html#ctypechar

I did a quick search for isspace in the GDAL source and there seems to
be some more places where isspace is passed a char instead of an
unsigned char.

Regards,
  Daniel Bäck

On 6/14/07, Daniel Morissette <dmorissette at mapgears.com> wrote:
> I've received a contributed patch recently to replace this same
> isspace() call with a call to iswspace(), claiming that isspace() could
> potentially "crash" when passed a wide char. The change is not in GDAL
> yet, it will be ported to the GDAL copy of the MITAB driver before the
> GDAL 1.5.0 release.
>
> I wonder if his "crash" might have been the same assert that you
> encountered and if yes then which fix between yours and his is better. I
> have contacted him to get his thoughts but haven't received any reply
> yet. I'd welcome your comments too.
>
> Daniel
>
>
>
> Daniel wrote:
> > Hello,
> >
> > If you build GDAL against the debug version of the c-runtime with
> > Visual Studio 2005 (/MDd) and try to open a .tab file with 8-bit ASCII
> > characters in it, the field names for instance, you get an assert in
> > isspace on row 177 in
> > http://trac.osgeo.org/gdal/browser/trunk/gdal/ogr/ogrsf_frmts/mitab/mitab_imapinfofile.cpp
> >
> >
> > The parameter passed to isspace is a signed char which is converted to
> > a signed int so any values >127 will become negative. It seems to work
> > fine when built against the release libraries and if you ignore the
> > assert it seems to work so this is probably nothing serious maybe
> > depending on the locale that is used. It can easily be fixed by
> > casting the char to an unsigend char before passing it to isspace:
> > isspace((unsigned char)*pszLine)
> >
> > Regards,
> >  Daniel Bäck
> >
> > _______________________________________________
> > Gdal-dev mailing list
> > Gdal-dev at lists.maptools.org
> > http://lists.maptools.org/mailman/listinfo/gdal-dev
>
>
> --
> Daniel Morissette
> http://www.mapgears.com/
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