[luatex] some bits of opentype math testing

Taco Hoekwater taco at elvenkind.com
Wed Jul 28 08:06:37 CEST 2010

On 07/28/2010 02:00 AM, Ulrik Vieth wrote:
> On 07/27/2010 03:23 PM, Taco Hoekwater wrote:
>> Ok, thanks. I found and corrected a bug in luatex: the last 'single'
>> glyph in a chained list was always ignored because the fact that it
>> had extensible tags took precedence over its actual size.
> Hi Taco,
> just out of curiosity: How do you actually debug such issues?
> Are there extra tracing hooks in LuaTeX you can activate?
> Do you compile a special version with extra debug prints?
> Do you single-step through the TeX engine in a debugger?

Any and all of the above, but mostly by using the gdb debugger and
valgrind (http://valgrind.org/) on a minimal input file. Font
issues start with fontforge to check the font itself, just in case.
Actual luatex crashes always start with a valgrind run, because
most often these are caused by some kind of memory allocation error.

It helps that I know a lot of the luatex code by heart, so that I
normally know what code to check beforehand, and in the cases where
I am not very familiar with the code I usually delegate the
problem to Hartmut.

My local version of luatex is always compiled without optimizations
and with all possible compiler warnings turned on, and the build.sh
script supports a --make option that makes it recompile only the
needed C files.

> Is there anything, we could use as well to diagnose problems?

For actual debugging, it depends on how brave you are, debugging
something as large as luatex is definitely not for the faint of
heart. When trying to diagnose problems, a minimal test file is
always needed, so it helps a lot if there was such a file included
in the bug report.

Best wishes,

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