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twagraph: fix merge_states() on automata without edges

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This corner case was simply causing segfaults.

* tests/python/mergedge.py: Add a test case.
* spot/twa/twagraph.cc (merge_states): Add special handling for
the case where the automaton has no edges.
This commit is contained in:
Alexandre Duret-Lutz 2023-09-20 00:00:15 +02:00
parent 202ab92d1d
commit 858629dd3a
2 changed files with 39 additions and 6 deletions
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23
spot/twa/twagraph.cc
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@ -363,6 +363,24 @@ namespace spot
throw std::runtime_error(
"twa_graph::merge_states() does not work on alternating automata");
const unsigned n_states = num_states();
const auto& e_vec = edge_vector();
unsigned n_edges = e_vec.size();
if (n_edges <= 1)
{
if (n_states == 1)
return 0;
// We don't have a very convenient way to resize the state
// vector.
std::vector<unsigned> remap(n_states, -1U);
remap[0] = 0;
get_graph().defrag_states(remap, 1);
SPOT_ASSERT(num_states() == 1);
set_init_state(0);
return n_states - 1;
}
#ifdef ENABLE_PTHREAD
const unsigned nthreads = ppolicy.nthreads();
#else
@ -387,8 +405,6 @@ namespace spot
}, nthreads);
g_.chain_edges_();
const unsigned n_states = num_states();
// Edges are nicely chained and there are no erased edges
// -> We can work with the edge_vector
@ -406,9 +422,6 @@ namespace spot
for (unsigned i = 0; i < n_states; ++i)
hash_of_state.push_back(i);
const auto& e_vec = edge_vector();
unsigned n_edges = e_vec.size();
// For each state we need 4 indices of the edge vector
// [first, first_non_sfirst_selflooplfloop, first_selfloop, end]
// The init value makes sure nothing is done for dead end states