[matthiaskoenig]

Fixes #503.

UnitDefinition::areIdentical copies both unit definitions to simplify and reorder them, on the heap, and deletes the copies at the end. The early return identical; for overall multipliers which differ skipped the deletes, so every call which compares unit definitions with different multipliers leaked both copies with their units (about 11 kB per call). As suggested in the issue, the copies are allocated on the stack now, so every return releases them; the logic is unchanged.

Check (a C++ reproduction of the issue, linked against the shared library built from development and from this branch, under valgrind --leak-check=full, 100 iterations of areIdentical(mass, rate) with different multipliers and areIdentical(rate, rate2) with equal overall multipliers):

	result	valgrind
development	100 of 200 identical	definitely lost 451,200 bytes in 200 blocks, indirectly lost 640,000 bytes
this branch	100 of 200 identical	all heap blocks were freed, no leaks are possible

areEquivalent and areIdenticalSIUnits already delete their copies on every return.

[fbergmann]

@matthiaskoenig thank you so much for the PR, this solves the issue.

the test failures are unrelated to this issue, I'll leave this PR open, so I can add the necessary commits and merge at the end of the week with those issues solved.

Do you need a new release right away?

[matthiaskoenig]

It would be great to have a release as soon as possible (but this is not blocking anything at the moment).

You and Sarah fixed a ton of issues in the last week for which I have a lot of work around code in my code base (e.g. I have a own areIdentical for units in python, but calling this 100.000 of times which is very slow but I cannot afford the memory loss ;).

I would really like to get rid of all the unnecessary code and checks on my side, because things have been fixed upstream in libsbml.

Best

[fbergmann]

@matthiaskoenig I'll make it a priority and aim for a release Wed, Thursday at the latest.

@skeating that would be fine with you, right?