diff --git a/cola/libcola/cc_nonoverlapconstraints.cpp b/cola/libcola/cc_nonoverlapconstraints.cpp
index 69502d09..8ff40bc4 100644
--- a/cola/libcola/cc_nonoverlapconstraints.cpp
+++ b/cola/libcola/cc_nonoverlapconstraints.cpp
@@ -199,9 +199,9 @@ void NonOverlapConstraints::computeOverlapForShapePairInfo(ShapePairInfo& info,
     {
         COLA_ASSERT(shape1.halfDim[0] == 0);
         COLA_ASSERT(shape1.halfDim[1] == 0);
-        COLA_ASSERT(info.varIndex1 + 1 < vs[0].size());
+        COLA_ASSERT(info.varIndex1 + 1U < vs[0].size());
         right1 = vs[0][info.varIndex1 + 1]->finalPosition;
-        COLA_ASSERT(info.varIndex1 + 1 < vs[1].size());
+        COLA_ASSERT(info.varIndex1 + 1U < vs[1].size());
         top1    = vs[1][info.varIndex1 + 1]->finalPosition;
         left1 -= shape1.rectPadding.min(XDIM);
         bottom1 -= shape1.rectPadding.min(YDIM);
@@ -218,9 +218,9 @@ void NonOverlapConstraints::computeOverlapForShapePairInfo(ShapePairInfo& info,
     {
         COLA_ASSERT(shape2.halfDim[0] == 0);
         COLA_ASSERT(shape2.halfDim[1] == 0);
-        COLA_ASSERT(info.varIndex2 + 1 < vs[0].size());
+        COLA_ASSERT(info.varIndex2 + 1U < vs[0].size());
         right2 = vs[0][info.varIndex2 + 1]->finalPosition;
-        COLA_ASSERT(info.varIndex2 + 1 < vs[1].size());
+        COLA_ASSERT(info.varIndex2 + 1U < vs[1].size());
         top2   = vs[1][info.varIndex2 + 1]->finalPosition;
         left2 -= shape2.rectPadding.min(XDIM);
         bottom2 -= shape2.rectPadding.min(YDIM);
diff --git a/cola/libdialect/chains.cpp b/cola/libdialect/chains.cpp
index 2aa26b7a..87f5d874 100644
--- a/cola/libdialect/chains.cpp
+++ b/cola/libdialect/chains.cpp
@@ -429,7 +429,7 @@ BendSequences Chain::computePossibleBendSequences(void) const {
         try {
             CardinalDir dIn = m_graph->getSepMatrix().getCardinalDir(A->id(), b->id());
             inDirs.push_back(dIn);
-        } catch (std::runtime_error) {
+        } catch (std::runtime_error const&) {
             // In this case the left anchor edge is not yet aligned, so we get to consider
             // both possible non-aggressive alignments of it.
             inDirs = possibleCardinalDirections(A, b);
@@ -438,7 +438,7 @@ BendSequences Chain::computePossibleBendSequences(void) const {
         try {
             CardinalDir dOut = m_graph->getSepMatrix().getCardinalDir(y->id(), Z->id());
             outDirs.push_back(dOut);
-        } catch (std::runtime_error) {
+        } catch (std::runtime_error const&) {
             outDirs = possibleCardinalDirections(y, Z);
         }
         // Now we can look up the possible bend sequences.
diff --git a/cola/libdialect/constraints.cpp b/cola/libdialect/constraints.cpp
index 439ce75a..942a73a2 100644
--- a/cola/libdialect/constraints.cpp
+++ b/cola/libdialect/constraints.cpp
@@ -72,6 +72,8 @@ SepDir dialect::negateSepDir(SepDir sd) {
         return SepDir::RIGHT;
     case SepDir::UP:
         return SepDir::DOWN;
+    default :
+        COLA_ASSERT(false);
     }
 }
 
@@ -112,6 +114,8 @@ SepDir dialect::cardinalDirToSepDir(CardinalDir dir) {
         return SepDir::WEST;
     case CardinalDir::NORTH:
         return SepDir::NORTH;
+    default:
+        COLA_ASSERT(false);
     }
 }
 
@@ -317,8 +321,8 @@ string SepPair::writeTglf(std::map<id_type, unsigned> id2ext, const SepMatrix &m
            ygtStr = ygt == GapType::BDRY ? "B" : "C";
     // Prepare indices.
     unsigned src, tgt;
-    try { src = id2ext.at(this->src); } catch (std::out_of_range) { src = this->src; }
-    try { tgt = id2ext.at(this->tgt); } catch (std::out_of_range) { tgt = this->tgt; }
+    try { src = id2ext.at(this->src); } catch (std::out_of_range const&) { src = this->src; }
+    try { tgt = id2ext.at(this->tgt); } catch (std::out_of_range const&) { tgt = this->tgt; }
     std::ostringstream ss;
     // Vertically aligned
     if (xgt == GapType::CENTRE && xst == SepType::EQ && xgap == 0) {
diff --git a/cola/libdialect/graphs.cpp b/cola/libdialect/graphs.cpp
index 17236960..ad575034 100644
--- a/cola/libdialect/graphs.cpp
+++ b/cola/libdialect/graphs.cpp
@@ -110,6 +110,9 @@ LineSegment_SP BoundingBox::buildSideSegment(CardinalDir side) const {
         return std::make_shared<LineSegment>(Point(x, Y), Point(X, Y));
     case CardinalDir::NORTH:
         return std::make_shared<LineSegment>(Point(x, y), Point(X, y));
+    default:
+        COLA_ASSERT(false);
+
     }
 }
 
@@ -826,7 +829,7 @@ bool Graph::hasSameLayoutAs(const Graph &other, double tol, id_map *idMap) const
                 ++it; ++jt;
             }
         }
-    } catch (std::out_of_range) {
+    } catch (std::out_of_range const&) {
         // We invoke the .at() method of various maps, above.
         // If any of these fails, the two Graphs do not have the same layout.
         return false;
@@ -1055,7 +1058,7 @@ bool Graph::applyProjSeq(const ColaOptions &opts, ProjSeq &ps, int accept) {
     double iel = opts.idealEdgeLength;
     if (iel == 0) iel = getIEL();
     // Do stress computations iff iel >= 0.
-    double lastStress;
+    double lastStress = 0.0;
     if (iel >= 0) lastStress = computeStress();
     // We will check whether all projections work.
     bool allOK = true;
diff --git a/cola/libdialect/io.cpp b/cola/libdialect/io.cpp
index d8084d50..84f99694 100644
--- a/cola/libdialect/io.cpp
+++ b/cola/libdialect/io.cpp
@@ -108,13 +108,14 @@ Graph_SP dialect::buildGraphFromTglf(istream &in) {
             COLA_ASSERT(iss >> i1 >> i2 >> gtc >> dir >> rel1 >> rel2 >> gap);
             id_type j1 = nodesByExternalId[i1]->id(),
                     j2 = nodesByExternalId[i2]->id();
-            GapType gt;
-            SepDir sd;
-            SepType st;
+            GapType gt{};
+            SepDir sd{};
+            SepType st{};
             switch(gtc) {
                 case 'B': gt=GapType::BDRY; break;
                 case 'C': gt=GapType::CENTRE; break;
-                COLA_ASSERT(false);
+                default:
+                    COLA_ASSERT(false);
             }
             switch(dir) {
                 case 'E': sd=SepDir::EAST; break;
@@ -127,12 +128,14 @@ Graph_SP dialect::buildGraphFromTglf(istream &in) {
                 case 'U': sd=SepDir::UP; break;
                 case 'X': sd=SepDir::RIGHT; break;
                 case 'Y': sd=SepDir::DOWN; break;
-                COLA_ASSERT(false);
+                default:
+                    COLA_ASSERT(false);
             }
             switch(rel1) {
                 case '=': st=SepType::EQ; break;
                 case '>': st=SepType::INEQ; break;
-                COLA_ASSERT(false);
+                default:
+                    COLA_ASSERT(false);
             }
             graph->getSepMatrix().addSep(j1, j2, gt, sd, st, gap);
             break;
diff --git a/cola/libdialect/ortho.cpp b/cola/libdialect/ortho.cpp
index af71f28d..e3f9ac7b 100644
--- a/cola/libdialect/ortho.cpp
+++ b/cola/libdialect/ortho.cpp
@@ -151,6 +151,8 @@ Point Compass::vectorSigns(CompassDir d) {
     case CompassDir::NW:    return Point(-1, -1);
     case CompassDir::NORTH: return Point( 0, -1);
     case CompassDir::NE:    return Point( 1, -1);
+    default:
+        COLA_ASSERT(false);
     }
 }
 
@@ -249,6 +251,8 @@ std::string Compass::dirToString(CompassDir d) {
     case CompassDir::SW: return "SW";
     case CompassDir::NW: return "NW";
     case CompassDir::NE: return "NE";
+    default :
+        COLA_ASSERT(false);
     }
 }
 
@@ -258,6 +262,8 @@ std::string Compass::cardToString(CardinalDir d) {
     case CardinalDir::SOUTH: return "SOUTH";
     case CardinalDir::WEST: return "WEST";
     case CardinalDir::NORTH: return "NORTH";
+    default:
+        COLA_ASSERT(false);
     }
 }
 
diff --git a/cola/libdialect/quadaction.cpp b/cola/libdialect/quadaction.cpp
index 034280bf..035bd404 100644
--- a/cola/libdialect/quadaction.cpp
+++ b/cola/libdialect/quadaction.cpp
@@ -107,9 +107,9 @@ string Assignment::toString() const {
     return s;
 }
 
-Quad::Quad(unsigned num) : num(num) {
+Quad::Quad(unsigned int num) : num(num) {
     // The only valid num's for quadrants are 0, 1, 2, 3.
-    COLA_ASSERT(0 <= num && num <= 3);
+    COLA_ASSERT(num <= 3);
 }
 
 void Quad::sortAndComputeCosts() {
diff --git a/cola/libdialect/quadaction.h b/cola/libdialect/quadaction.h
index 38f29340..5e6edb07 100644
--- a/cola/libdialect/quadaction.h
+++ b/cola/libdialect/quadaction.h
@@ -141,7 +141,7 @@ struct Quad {
     //! @brief  Standard constructor.
     //!
     //! @param[in]  num  The number of this quadrant in {0, 1, 2, 3}
-    Quad(unsigned num);
+    Quad(unsigned int num);
 
     //! @brief  Add a neighbour.
     void addNbr(const Nbr_SP &nbr) { nbrs.push_back(nbr); }
diff --git a/cola/libdialect/routing.cpp b/cola/libdialect/routing.cpp
index 9709bfed..dad79e37 100644
--- a/cola/libdialect/routing.cpp
+++ b/cola/libdialect/routing.cpp
@@ -145,9 +145,11 @@ void RoutingAdapter::recordRoutes(bool refine) {
             // in the window are within epsilon of one another (in both dimensions),
             // we will skip both.
             vector<Point> refined_pts;
-            size_t N = pts.size() - 2;  // the number of interior points
+            size_t M = pts.size();
             // We expect that there are at least two route points.
-            COLA_ASSERT(N >= 0);
+            COLA_ASSERT( M >= 2);
+            // the number of interior points:
+            size_t N = M - 2;
             size_t i = 0;
             // We always keep the first route point.
             refined_pts.push_back(pts[0]);
diff --git a/cola/libdialect/util.h b/cola/libdialect/util.h
index 2af2bf03..a064ac5c 100644
--- a/cola/libdialect/util.h
+++ b/cola/libdialect/util.h
@@ -94,7 +94,7 @@ struct Matrix2d {
     std::string toString() const {
         std::string s = "";
         s += "\n  ";
-        char buffer [10];
+        char buffer [21];
         for (int j=0; j<cols; j++) {
             sprintf(buffer," %2d",j);
             s += std::string(buffer);
diff --git a/cola/libvpsc/rectangle.cpp b/cola/libvpsc/rectangle.cpp
index 6d80c348..4b07f4a6 100644
--- a/cola/libvpsc/rectangle.cpp
+++ b/cola/libvpsc/rectangle.cpp
@@ -399,6 +399,7 @@ inline bool checkIntersection(
         ri.intersects=side=true;
         sideX=intersection.x_;
         sideY=intersection.y_;
+        return true;
     case LineSegment::PARALLEL:
     case LineSegment::NOT_INTERSECTING:
         return true;
diff --git a/cola/libvpsc/rectangle.h b/cola/libvpsc/rectangle.h
index df763993..df302909 100644
--- a/cola/libvpsc/rectangle.h
+++ b/cola/libvpsc/rectangle.h
@@ -89,13 +89,10 @@ class Rectangle {
      */
     Rectangle(double x, double X, double y, double Y,
             bool allowOverlap = false);
-    Rectangle(Rectangle const &Other)
-        :  minX(Other.minX)
-        ,  maxX(Other.maxX)
-        ,  minY(Other.minY)
-        ,  maxY(Other.maxY)
-        ,  overlap(Other.overlap) { }
+    Rectangle(const Rectangle &Other) = default;
     Rectangle();
+    ~Rectangle() {}
+
     bool isValid(void) const;
     Rectangle unionWith(const Rectangle& rhs) const;
     /*