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Model construction has to respect the length constraints

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CEisenhofer 2026-04-22 19:51:09 +02:00
parent 0a1eb26952
commit 3873f387be
6 changed files with 72 additions and 16 deletions
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25
src/smt/seq_model.cpp
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@ -495,6 +495,29 @@ namespace smt {
if (m_var_regex.find(key, re) && re) {
expr* re_expr = re->get_expr();
SASSERT(re_expr);
arith_util arith(m);
expr_ref len_expr(m_seq.str.mk_length(var->get_expr()), m);
rational len_val;
bool has_len = false;
if (dep_values) {
expr* dval = nullptr;
enode* dep = find_root_enode(m_ctx, len_expr);
if (dep && dep_values->find(dep, dval) && dval && arith.is_numeral(dval, len_val))
has_len = true;
}
if (!has_len && m_mg) {
expr_ref eval_len(m);
if (m_mg->get_model().eval(len_expr, eval_len, true) && arith.is_numeral(eval_len, len_val))
has_len = true;
}
if (has_len && len_val.is_unsigned()) {
unsigned n = len_val.get_unsigned();
expr_ref loop(m_seq.re.mk_loop(m_seq.re.mk_full_char(re_expr->get_sort()), n, n), m);
re_expr = m_seq.re.mk_inter(re_expr, loop);
}
expr_ref witness(m);
// We checked non-emptiness during Nielsen already
lbool wr = m_rewriter.some_seq_in_re(re_expr, witness);
@ -503,7 +526,7 @@ namespace smt {
m_factory->register_value(witness);
return witness;
}
IF_VERBOSE(1, verbose_stream() << "witness extraction failed: " << wr << "\n" << mk_pp(re_expr, m) << "\n");
IF_VERBOSE(1, verbose_stream() << "witness extraction failed: " << wr << " with len " << (has_len ? len_val.to_string() : "unknown") << "\n" << mk_pp(re_expr, m) << "\n");
UNREACHABLE();
}