It is not unlike other fuzz bugs: it exercises some behavior that applications are unlikely to expose. In this case, a rule body expanded into a conjunction with more than 1M formulas (with a lot of repetition). The original rule representation assumed silently that the number of constraints in a body would fit within 20 bits, but reality allowed bodies with as many as 2^{32} - 1 constraints.
So "minimizing" the bug as @agurfinkel asks for seems not to make too much sense.
Just running the samples in debug mode points to the root cause.
Since fuzz bugs are not from applications and fuzz tools have the potential for creating a large number of issues, I find it reasonable to push some basic pro-active asks on filers:
- reproduce bug in debug builds to assess whether a debug assert triggers.
- minimize or keep it simpler when possible (in this case it does not apply)
- perform basic diagnostics/triage. I am basically asking to push this part of the work on to the fuzzer. Otherwise, addressing random bugs doesn't scale. Triaging should have pointed to the root cause.
Now, there tends to be something to learn from bugs. In this case, the question was: "can we avoid constraints with duplications"? In particular, it points to a basic inefficiency of extracting conjunctions (and disjunctions). The function didn't deduplicate. So I added deduplication into this function. It is used throughout z3 code base so could expose latent issues. We will see.
- pull request might have new bugs given that build is broken.
- this test doesn't expose race conditions under simple tests, yet. It is a starting point.
- run under cuzz (app-verifier) should expose races, this is what it was made for.
* remove the bound on total iterations in simplex
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* remove unncesseray checks in get_freedom_interval_for_column()
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* fix the build of test-z3
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* Revert "remove unncesseray checks in get_freedom_interval_for_column()"
This reverts commit 6770ed85e3.
* optimize get_freedom_interval_for_column() for feasible case
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* add function lar_solver::status_feasible
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* rename status_is_feasible() to is_feasible()
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
* fix the linux build
Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
