[Dev-luatex] Strange code for font_param

luigi scarso luigi.scarso at gmail.com
Tue Nov 15 08:43:37 CET 2016

On Fri, Nov 11, 2016 at 8:49 PM, Lars Hamren <lh at sdu.se> wrote:
> Hi,
> I found some odd behaviour, arguably a bug or two, when I added bounds
> checking to _param_base,
> in struct texfont.
> As I have fixed this in my own code, this is just FYI.
> At about line 750 in mlist.w:
>         DEFINE_DMATH_PARAMETERS(math_param_radical_vgap, size_id,
>             (default_rule_thickness(size_id) + (abs(math_x_height(size_id))
> / 4)), lvl);
> default_rule_thickness turns out to be math parameter 8.
> But at least font 0 (nullfont) has only 7 parameters (according to
> _font_params).
> Parameters are Pascal-style (one-based) so there has to be one more element
> that parameters. Still, parameter 8 is outside the array bounds.
> But! When reallocating the _param_base array, the set_font_params()
> allocates
> not only one, but two, extra elements, so accessing parameter 8 works.
> The extra extra element is not initialized by set_font_params(), but
> either it is never actually used, or dynamic memory is zero-filled by
> default.
> These bugs are present int 0.95.0. They may or may not be present in later
> versions.
> Clarification: by bugs I mean a) accessing outside the logical bounds,
> and b) not initializing all elements.
> One quick way to fix it would be to check the parameter number in
> font_param(),
> and return 0 if out of bounds.
> Regards
> /Lars

Thank you very much for your report and  my apologies for delay of the answer.
We are currently quite busy but there should be a debugging session at
the end of current month,
and we will see this issue as the others as well.


More information about the dev-luatex mailing list