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fix complete

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Alexandre Lewkowicz reported a case where complete() would peek an
existing state that is accepting, and wrongly use it as a sink.

* spot/twaalgos/complete.cc: Fix the function.
* tests/core/complete.test: Add two more tests.
* NEWS: Mention the bug.
This commit is contained in:
Alexandre Duret-Lutz 2016-01-14 17:14:01 +01:00
parent 6c62362fe9
commit 51483b9b7f
3 changed files with 85 additions and 14 deletions
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34
spot/twaalgos/complete.cc
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@ -45,27 +45,38 @@ namespace spot
}
else
{
// Loop over the states and seek a state that has only self
// loops, and that is not accepting. This will be our sink
// state. Note that we do not even have to ensure that the
// state is complete as we will complete the whole automaton
// in a second pass.
// Loop over the states and search a state that has only self
// loop labeled by the same non-accepting mark. This will be
// our sink state. Note that we do not even have to ensure
// that the state is complete as we will complete the whole
// automaton in a second pass.
for (unsigned i = 0; i < n; ++i)
{
bool selfloop = true;
acc_cond::mark_t accsum = 0U;
bool sinkable = true;
bool first = true;
acc_cond::mark_t commonacc = 0U;
for (auto& t: aut->out(i))
{
if (t.dst != i) // Not a self-loop
{
selfloop = false;
sinkable = false;
break;
}
if (first)
{
commonacc = t.acc;
first = false;
}
else if (t.acc != commonacc)
{
sinkable = false;
break;
}
accsum |= t.acc;
}
if (selfloop && !aut->acc().accepting(accsum))
if (sinkable && !aut->acc().accepting(commonacc))
{
// We have found a sink!
um.second = commonacc;
sink = i;
break;
}
@ -74,8 +85,7 @@ namespace spot
unsigned t = aut->num_edges();
// If the automaton is empty,
// pretend that state
// If the automaton is empty, pretend that state 0 is a sink.
if (t == 0)
sink = init;