Debug dlist insertion

Found because of assertion failure in
test_polysat::test_fixed_point_arith_div_mul_inverse()

src/math/polysat/viable.cpp

@@ -75,18 +75,18 @@ namespace polysat {
     }
 
     void viable::pop_viable() {
-        auto& [v, k, e] = m_trail.back();
+        auto const& [v, k, e] = m_trail.back();
         SASSERT(well_formed(m_units[v]));
         switch (k) {
         case entry_kind::unit_e:
-            e->remove_from(m_units[v], e);
+            entry::remove_from(m_units[v], e);
             SASSERT(well_formed(m_units[v]));
             break;
         case entry_kind::equal_e:
-            e->remove_from(m_equal_lin[v], e);
+            entry::remove_from(m_equal_lin[v], e);
             break;
         case entry_kind::diseq_e:
-            e->remove_from(m_diseq_lin[v], e);
+            entry::remove_from(m_diseq_lin[v], e);
             break;
         default:
             UNREACHABLE();
@@ -104,7 +104,9 @@ namespace polysat {
         (void)k;
         SASSERT(well_formed(m_units[v]));
         if (e->prev() != e) {
-            e->prev()->insert_after(e);
+            entry* pos = e->prev();
+            e->init(e);
+            pos->insert_after(e);
             if (e->interval.lo_val() < m_units[v]->interval.lo_val())
                 m_units[v] = e;
         }
@@ -180,6 +182,7 @@ namespace polysat {
             entries[v] = e;
         else
             e->insert_after(entries[v]);
+        SASSERT(entries[v]->invariant());
         SASSERT(well_formed(m_units[v]));
     }
 
@@ -272,10 +275,10 @@ namespace polysat {
     */
     bool viable::refine_equal_lin(pvar v, rational const& val) {
         // LOG_H2("refine-equal-lin with v" << v << ", val = " << val);
-        auto* e = m_equal_lin[v];
+        entry const* e = m_equal_lin[v];
         if (!e)
             return true;
-        entry* first = e;
+        entry const* first = e;
         rational const& max_value = s.var2pdd(v).max_value();
         rational mod_value = max_value + 1;
 
@@ -380,10 +383,10 @@ namespace polysat {
 
     bool viable::refine_disequal_lin(pvar v, rational const& val) {
         // LOG_H2("refine-disequal-lin with v" << v << ", val = " << val);
-        auto* e = m_diseq_lin[v];
+        entry const* e = m_diseq_lin[v];
         if (!e)
             return true;
-        entry* first = e;
+        entry const* first = e;
         rational const& max_value = s.var2pdd(v).max_value();
         rational const mod_value = max_value + 1;
 
@@ -632,9 +635,9 @@ namespace polysat {
     bool viable::resolve(pvar v, conflict& core) {
         if (has_viable(v))
             return false;
-        auto* e = m_units[v];
+        entry const* e = m_units[v];
         // TODO: in the forbidden interval paper, they start with the longest interval. We should also try that at some point.
-        entry* first = e;
+        entry const* first = e;
         SASSERT(e);
         // If there is a full interval, all others would have been removed
         SASSERT(!e->interval.is_full() || e->next() == e);
@@ -642,7 +645,7 @@ namespace polysat {
         do {
             // Build constraint: upper bound of each interval is not contained in the next interval,
             // using the equivalence:  t \in [l;h[  <=>  t-l < h-l
-            entry* n = e->next();
+            entry const* n = e->next();
 
             // Choose the next interval which furthest extends the covered region.
             // Example:
@@ -666,7 +669,7 @@ namespace polysat {
             //
             // The interval 'first' is always part of the lemma. If we reach first again here, we have covered the complete domain.
             while (n != first) {
-                entry* n1 = n->next();
+                entry const* n1 = n->next();
                 // Check if n1 is eligible; if yes, then n1 is better than n.
                 //
                 // Case 1, n1 overlaps e (unless n1 == e):

src/math/polysat/viable.h

@@ -38,7 +38,7 @@ namespace polysat {
         solver& s;
         forbidden_intervals      m_forbidden_intervals;
 
-        struct entry : public dll_base<entry>, public fi_record {};
+        struct entry final : public dll_base<entry>, public fi_record {};
         enum class entry_kind { unit_e, equal_e, diseq_e };
 
         ptr_vector<entry>                    m_alloc;

src/util/debug.h

@@ -19,6 +19,7 @@ Revision History:
 #pragma once
 
 #include <stdlib.h>
+#include <iostream>
 
 void enable_assertions(bool f);
 bool assertions_enabled();

src/util/dlist.h

@@ -18,14 +18,25 @@ Revision History:
 --*/
 #pragma once
 #include <type_traits>
+#include "util/debug.h"
+#include "util/util.h"
 
 template <typename T> class dll_iterator;
 
 template <typename T>
 class dll_base {
-    T* m_next { nullptr };
-    T* m_prev { nullptr };
+    T* m_next = nullptr;
+    T* m_prev = nullptr;
+
+protected:
+    dll_base() = default;
+    ~dll_base() = default;
+
 public:
+    dll_base(dll_base const&) = delete;
+    dll_base(dll_base&&) = delete;
+    dll_base& operator=(dll_base const&) = delete;
+    dll_base& operator=(dll_base&&) = delete;
 
     T* prev() { return m_prev; }
     T* next() { return m_next; }
@@ -35,6 +46,7 @@ public:
     void init(T* t) {
         m_next = t;
         m_prev = t;
+        SASSERT(invariant());
     }
 
     static T* pop(T*& list) {
@@ -45,23 +57,61 @@ public:
         return head;
     }
 
-    void insert_after(T* elem) {
+    void insert_after(T* other) {
+#ifndef NDEBUG
+        SASSERT(other);
+        SASSERT(invariant());
+        SASSERT(other->invariant());
+        unsigned const old_sz1 = count_if(*static_cast<T*>(this), [](T const&) { return true; });
+        unsigned const old_sz2 = count_if(*other, [](T const&) { return true; });
+#endif
+        // have:        this -> next -> ...
+        // insert:      other -> ... -> other_end
+        // result:      this -> other -> ... -> other_end -> next -> ...
         T* next = this->m_next;
-        elem->m_prev = next->m_prev;
-        elem->m_next = next;
-        this->m_next = elem;
-        next->m_prev = elem;
+        T* other_end = other->m_prev;
+        this->m_next = other;
+        other->m_prev = static_cast<T*>(this);
+        other_end->m_next = next;
+        next->m_prev = other_end;
+#ifndef NDEBUG
+        SASSERT(invariant());
+        SASSERT(other->invariant());
+        unsigned const new_sz = count_if(*static_cast<T*>(this), [](T const&) { return true; });
+        SASSERT_EQ(new_sz, old_sz1 + old_sz2);
+#endif
     }
 
-    void insert_before(T* elem) {
+    void insert_before(T* other) {
+#ifndef NDEBUG
+        SASSERT(other);
+        SASSERT(invariant());
+        SASSERT(other->invariant());
+        unsigned const old_sz1 = count_if(*static_cast<T*>(this), [](T const&) { return true; });
+        unsigned const old_sz2 = count_if(*other, [](T const&) { return true; });
+#endif
+        // have:        prev -> this -> ...
+        // insert:      other -> ... -> other_end
+        // result:      prev -> other -> ... -> other_end -> this -> ...
         T* prev = this->m_prev;
-        elem->m_next = prev->m_next;
-        elem->m_prev = prev;
-        prev->m_next = elem;
-        this->m_prev = elem;
+        T* other_end = other->m_prev;
+        prev->m_next = other;
+        other->m_prev = prev;
+        other_end->m_next = static_cast<T*>(this);
+        this->m_prev = other_end;
+#ifndef NDEBUG
+        SASSERT(invariant());
+        SASSERT(other->invariant());
+        unsigned const new_sz = count_if(*static_cast<T*>(this), [](T const&) { return true; });
+        SASSERT_EQ(new_sz, old_sz1 + old_sz2);
+#endif
     }
     
     static void remove_from(T*& list, T* elem) {
+        SASSERT(list);
+        SASSERT(elem);
+        SASSERT(list->invariant());
+        SASSERT(elem->invariant());
         if (list->m_next == list) {
             SASSERT(elem == list);
             list = nullptr;
@@ -73,6 +123,7 @@ public:
         auto* prev = elem->m_prev;
         prev->m_next = next;
         next->m_prev = prev;        
+        SASSERT(list->invariant());
     }
 
     static void push_to_front(T*& list, T* elem) {
@@ -141,10 +192,11 @@ public:
         return {elem, false};
     }
 
-    // using value_type = T;
-    // using pointer = T const*;
-    // using reference = T const&;
-    // using iterator_category = std::input_iterator_tag;
+    using value_type = T;
+    using pointer = T const*;
+    using reference = T const&;
+    using iterator_category = std::input_iterator_tag;
+    using difference_type = std::ptrdiff_t;
 
     dll_iterator& operator++() {
         m_elem = m_elem->next();

src/util/util.h

@@ -379,10 +379,10 @@ inline size_t megabytes_to_bytes(unsigned mb) {
 
 /** Compact version of std::all_of */
 template <typename Container, typename Predicate>
-bool all_of(Container const& c, Predicate f)
+bool all_of(Container const& c, Predicate p)
 {
     using std::begin, std::end;  // allows begin(c) to also find c.begin()
-    return std::all_of(begin(c), end(c), std::forward<Predicate>(f));
+    return std::all_of(begin(c), end(c), std::forward<Predicate>(p));
 }
 
 /** Compact version of std::count */
@@ -392,3 +392,11 @@ std::size_t count(Container const& c, Item x)
     using std::begin, std::end;  // allows begin(c) to also find c.begin()
     return std::count(begin(c), end(c), std::forward<Item>(x));
 }
+
+/** Compact version of std::count_if */
+template <typename Container, typename Predicate>
+std::size_t count_if(Container const& c, Predicate p)
+{
+    using std::begin, std::end;  // allows begin(c) to also find c.begin()
+    return std::count_if(begin(c), end(c), std::forward<Predicate>(p));
+}