Randomized tests in CppunitTest_basegfx

[Michael Meeks]

Hi Stephan,

On 22/02/2023 10:54, Stephan Bergmann wrote:
> <https://ci.libreoffice.org//job/lo_ubsan/2691> failed 
> CppunitTest_basegfx with
...
> in testTrapezoidHelper that had originally been introduced in 
> <https://git.libreoffice.org/core/+/82b56544a7a53528970632d086c3cfd8ef879335%5E!/> 
> "basegfx: accelerate Trapezoid subdivision by avoiding allocations" and 
> apparently uses random data (via basegfx2d::getRandomOrdinal, defined in 
> basegfx/test/boxclipper.cxx), so that runs of CppunitTest_basegfx are 
> not reproducible (so that there's no good way to reproduce and fix the 
> above division by zero error).  Can that test be made reproducible please?

	Ooh - interesting; so would using the boxclipper's getRandomOrdinal - 
which uses rand() and (I assume) could be consistently seeded ?

	Or could we consistently seed:

	comphelper::rng::uniform_size_distribution(

	To produced a known pattern ? or we could hard-code a set of numbers 
(which I guess) wouldn't provoke the problem into the test.

	Would be lovely to find the sequence that kills it of course,

	Thoughts much appreciated,

		Michael.

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