Initialize version sooner in VersionedMap::begin

Facade.h

@@ -138,12 +138,16 @@ struct Facade {
             String(m.param2, m.param2Len);
         break;
       case weaselab::VersionedMap::Clear:
+        if (m.param2Len == 0) {
+          unversioned.erase(String(m.param1, m.param1Len));
+        } else {
           for (auto unversionedIter =
                    unversioned.lower_bound(String(m.param1, m.param1Len));
                unversionedIter != unversioned.end() &&
                unversionedIter->first < String(m.param2, m.param2Len);) {
             unversionedIter = unversioned.erase(unversionedIter);
           }
+        }
         break;
       }
     }

FacadeFuzz.cpp

@@ -2,6 +2,7 @@
 #include "Internal.h"
 #include "KeyCompare.h"
 
+#include <inttypes.h>
 #include <map>
 #include <set>
 
@@ -81,10 +82,13 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case 1: {
       // Set oldest version
 
-      facade.setOldestVersion(facade.getOldestVersion() +
+      const int64_t newOldestVersion =
-                              gArbitrary.bounded(facade.getVersion() -
           facade.getOldestVersion() +
-                                                 1));
+          gArbitrary.bounded(facade.getVersion() - facade.getOldestVersion() +
+                             1);
+
+      facade.setOldestVersion(newOldestVersion);
+
     } break;
     case 2: {
       // Check range read

RootSet.cpp

@@ -123,6 +123,11 @@ struct RootSet::Impl {
       firstToFree = firstToFree->next;
       safe_free(tmp, ThreadSafeHandle::Impl::sizeForCapacity(tmp->capacity));
     }
+#ifndef NDEBUG
+    assert(rootCount() > 0);
+    auto *h = handle.load(std::memory_order_relaxed);
+    assert(h->versions()[h->lastLeq(oldestVersion)] <= oldestVersion);
+#endif
   }
 
   const uint32_t *roots() const {

VersionedMap.cpp

@@ -262,62 +262,49 @@ struct MemManager {
   }
 
   void gc(const uint32_t *roots, int numRoots, int64_t oldestVersion) {
-#if DEBUG_VERBOSE
-    if (debugVerboseEnabled) {
-      printf("GC roots:\n");
-      for (int i = 0; i < numRoots; ++i) {
-        printf("  %u\n", roots[i]);
-      }
-    }
-#endif
     // Calculate reachable set
     BitSet reachable{next};
     // Each node has at most 3 children and nodes along the search path aren't
     // in the stack, so we need 2 * kPathLengthUpperBound
     uint32_t stack[2 * kPathLengthUpperBound];
     int stackIndex = 0;
-    auto tryPush = [&](uint32_t p) {
+    auto tryPush = [&](uint32_t parent, uint32_t child) {
+      if (!reachable.set(child)) {
 #if DEBUG_VERBOSE
         if (debugVerboseEnabled) {
-        printf("  GC: visit: %u\n", p);
+          printf("  GC: reach: %u (parent %u)\n", child, parent);
-      }
-#endif
-      if (!reachable.set(p)) {
-#if DEBUG_VERBOSE
-        if (debugVerboseEnabled) {
-          printf("  GC: push on to stack: %u\n", p);
         }
 #endif
         assert(stackIndex < sizeof(stack) / sizeof(stack[0]));
-        stack[stackIndex++] = p;
+        stack[stackIndex++] = child;
       }
     };
     for (int i = 0; i < numRoots; ++i) {
       if (roots[i] == 0) {
         continue;
       }
-      tryPush(roots[i]);
+      tryPush(0, roots[i]);
       while (stackIndex > 0) {
         uint32_t p = stack[--stackIndex];
         auto &node = base[p];
         if (node.updated.load(std::memory_order_relaxed)) {
           if (node.pointer[!node.replacedPointer] != 0) {
-            tryPush(node.pointer[!node.replacedPointer]);
+            tryPush(p, node.pointer[!node.replacedPointer]);
           }
           if (oldestVersion < node.updateVersion) {
             if (node.pointer[node.replacedPointer] != 0) {
-              tryPush(node.pointer[node.replacedPointer]);
+              tryPush(p, node.pointer[node.replacedPointer]);
             }
           }
           if (node.pointer[2] != 0) {
-            tryPush(node.pointer[2]);
+            tryPush(p, node.pointer[2]);
           }
         } else {
           if (node.pointer[0] != 0) {
-            tryPush(node.pointer[0]);
+            tryPush(p, node.pointer[0]);
           }
           if (node.pointer[1] != 0) {
-            tryPush(node.pointer[1]);
+            tryPush(p, node.pointer[1]);
           }
         }
       }
@@ -495,6 +482,11 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
       result = n.pointer[which];
     }
     assert(result == 0 || result >= kMinAddressable);
+#ifndef NDEBUG
+    if (result != 0) {
+      assert(mm.base[result].entry != nullptr);
+    }
+#endif
     return result;
   }
 
@@ -1174,6 +1166,7 @@ void VersionedMap::firstGeq(const Key *key, const int64_t *version,
 VersionedMap::Iterator VersionedMap::begin(int64_t version) const {
   VersionedMap::Iterator result;
   result.impl = new (safe_malloc(sizeof(Iterator::Impl))) Iterator::Impl();
+  result.impl->version = version;
 
   bool ignored;
   result.impl->finger.push(
@@ -1205,7 +1198,6 @@ VersionedMap::Iterator VersionedMap::begin(int64_t version) const {
   }
   result.impl->mutationIndex = 0;
 
-  result.impl->version = version;
   return result;
 }