Ensure that we never end up with a seemingly valid bit count of 0.

2 files changed, 8 insertions, 9 deletions

diff --git a/searchlib/src/vespa/searchlib/common/allocatedbitvector.cpp b/searchlib/src/vespa/searchlib/common/allocatedbitvector.cpp
index 3de0c1f1320..08a3847f00d 100644
--- a/searchlib/src/vespa/searchlib/common/allocatedbitvector.cpp
+++ b/searchlib/src/vespa/searchlib/common/allocatedbitvector.cpp
@@ -52,6 +52,7 @@ AllocatedBitVector::AllocatedBitVector(Index numberOfElements, Index capacityBit
         }
         setBit(size()); // Guard bit
     }
+    updateCount();
 }
 
 AllocatedBitVector::AllocatedBitVector(const AllocatedBitVector & rhs) :
@@ -70,6 +71,8 @@ AllocatedBitVector::AllocatedBitVector(const BitVector & rhs, Index capacity_) :
     _capacityBits = computeCapacity(_capacityBits, _alloc.size());
     memcpy(_alloc.get(),  rhs.getStart(), rhs.sizeBytes());
     init(_alloc.get(), 0, rhs.size());
+    setBit(size());
+    updateCount();
 }
 
 //////////////////////////////////////////////////////////////////////
@@ -121,12 +124,9 @@ AllocatedBitVector::grow(Index newSize, Index newCapacity)
     if (newCapacity != capacity()) {
         AllocatedBitVector tbv(newSize, newCapacity, _alloc.get(), size());
         if (newSize > size()) {
-            tbv.clearBit(size());  // Clear old guard bit.
-        }
-        ret.reset(new GenerationHeldAlloc<Alloc>(_alloc));
-        if (( newSize >= size()) && isValidCount()) {
-            tbv.setTrueBits(countTrueBits());
+            tbv.clearBitAndMaintainCount(size());  // Clear old guard bit.
         }
+        ret = std::make_unique<GenerationHeldAlloc<Alloc>>(_alloc);
         swap(tbv);
     } else {
         if (newSize > size()) {
diff --git a/searchlib/src/vespa/searchlib/common/bitvector.h b/searchlib/src/vespa/searchlib/common/bitvector.h
index 98e8c9adad3..9671e41df24 100644
--- a/searchlib/src/vespa/searchlib/common/bitvector.h
+++ b/searchlib/src/vespa/searchlib/common/bitvector.h
@@ -45,7 +45,7 @@ public:
     }
     Index countTrueBits() const {
         if ( ! isValidCount()) {
-            _numTrueBits.store(count(), std::memory_order_relaxed);
+            updateCount();
         }
         return _numTrueBits.load(std::memory_order_relaxed);
     }
@@ -255,6 +255,7 @@ protected:
     BitVector(void * buf, Index sz) : BitVector(buf, 0, sz) { }
     BitVector() : BitVector(nullptr, 0) { }
     void init(void * buf,  Index start, Index end);
+    void updateCount() const { _numTrueBits.store(count(), std::memory_order_relaxed); }
     void setTrueBits(Index numTrueBits) { _numTrueBits.store(numTrueBits, std::memory_order_relaxed); }
     VESPA_DLL_LOCAL void clearIntervalNoInvalidation(Index start, Index end);
     bool isValidCount() const { return isValidCount(_numTrueBits.load(std::memory_order_relaxed)); }
@@ -340,7 +341,7 @@ private:
             func(start+pos);
             start += pos + 1;
             word >>= pos;
-            word >>= 1;
+            word >>= 1u;
         }
     }
 
@@ -357,8 +358,6 @@ protected:
     operator>>(vespalib::nbostream &in, BitVector &bv);
 };
 
-typedef BitVector ConstBitVectorReference;
-
 vespalib::nbostream &
 operator<<(vespalib::nbostream &out, const BitVector &bv);