diff --git a/Envelope_2/include/CGAL/Envelope_2/Env_divide_and_conquer_2_impl.h b/Envelope_2/include/CGAL/Envelope_2/Env_divide_and_conquer_2_impl.h
index 3acb28c4290..63bc9917dfd 100644
--- a/Envelope_2/include/CGAL/Envelope_2/Env_divide_and_conquer_2_impl.h
+++ b/Envelope_2/include/CGAL/Envelope_2/Env_divide_and_conquer_2_impl.h
@@ -627,8 +627,9 @@ _merge_two_intervals(Edge_const_handle e1, bool is_leftmost1,
   // This is the rightmost vertex in the current minimization diagram (out_d).
   // The intersection points/curves that interest us are the ones in
   // [v_leftmost, v].
+  // Without using make_optional we get a "maybe uninitialized" warning with gcc -Wall
   boost::optional<Vertex_const_handle>  v_leftmost =
-    boost::optional<Vertex_const_handle>();
+    boost::make_optional(false, Vertex_const_handle());
 
   if (is_leftmost1 == true) {
     if (is_leftmost2 == false)
diff --git a/Filtered_kernel/include/CGAL/internal/Static_filters/Compare_squared_radius_3.h b/Filtered_kernel/include/CGAL/internal/Static_filters/Compare_squared_radius_3.h
index 22b604213ca..d833cdcdc7d 100644
--- a/Filtered_kernel/include/CGAL/internal/Static_filters/Compare_squared_radius_3.h
+++ b/Filtered_kernel/include/CGAL/internal/Static_filters/Compare_squared_radius_3.h
@@ -65,6 +65,7 @@ namespace CGAL { namespace internal { namespace Static_filters_predicates {
                                     // but Lazy ones.
 
       double px, py, pz, qx, qy, qz, rx, ry, rz, sx, sy, sz, alpha;
+      init_double(px, py, pz, qx, qy, qz, rx, ry, rz, sx, sy, sz, alpha, (FT*)(0));
 
       if( fit_in_double(get_approx(p).x(), px) && fit_in_double(get_approx(p).y(), py)      &&
           fit_in_double(get_approx(p).z(), pz) && 
@@ -216,6 +217,8 @@ namespace CGAL { namespace internal { namespace Static_filters_predicates {
       CGAL_BRANCH_PROFILER_3("semi-static failures/attempts/calls to   : Compare_squared_radius_3 with 3 points", tmp);
       
       double px, py, pz, qx, qy, qz, sx, sy, sz, alpha;
+      init_double(px, py, pz, qx, qy, qz, sx, sy, sz, alpha, (FT*)(0));
+
       if( fit_in_double(p.x(), px) && fit_in_double(p.y(), py)      &&
           fit_in_double(p.z(), pz) && 
           fit_in_double(q.x(), qx) && fit_in_double(q.y(), qy)      &&
@@ -347,6 +350,7 @@ namespace CGAL { namespace internal { namespace Static_filters_predicates {
       CGAL_BRANCH_PROFILER_3("semi-static failures/attempts/calls to   : Compare_squared_radius_3 with 2 points", tmp);
       
       double px, py, pz, qx, qy, qz, alpha;
+      init_double(px, py, pz, qx, qy, qz, alpha, (FT*)(0));
       if( fit_in_double(p.x(), px) && fit_in_double(p.y(), py)      &&
           fit_in_double(p.z(), pz) && 
           fit_in_double(q.x(), qx) && fit_in_double(q.y(), qy)      &&
diff --git a/Filtered_kernel/include/CGAL/internal/Static_filters/tools.h b/Filtered_kernel/include/CGAL/internal/Static_filters/tools.h
index 5b249bea9c8..25561776008 100644
--- a/Filtered_kernel/include/CGAL/internal/Static_filters/tools.h
+++ b/Filtered_kernel/include/CGAL/internal/Static_filters/tools.h
@@ -39,6 +39,103 @@ inline bool diff_was_exact(double a, double b, double ab)
     return ab+b == a && a-ab == b;
 }
 
+template < typename T >
+inline void init_double(double&, T* ) {}
+
+template < typename T >
+inline void init_double(double&, double&, T* ) {}
+
+template < typename T >
+inline void init_double(double&, double&, double&, T* ) {}
+
+template < typename T >
+inline void init_double(double&, double&, double&, double&, T* ) {}
+
+template < typename T >
+inline void init_double(double&, double&, double&, double&, double&, T* ) {}
+
+template < typename T >
+inline void init_double(double&, double&, double&, double&, double&, double&, T* ) {}
+
+template < typename T >
+inline void init_double(double&, double&, double&, double&, double&, double&, double&, T* ) {}
+
+template < typename T >
+inline void init_double(double&, double&, double&, double&, double&, double&, double&, double&, T* ) {}
+
+template < typename T >
+inline void init_double(double&, double&, double&,double&, double&, double&, double&, double&, double&, T* ) {}
+
+template < typename T >
+inline void init_double(double&, double&, double&, double&, double&, double&, double&, double&, double&, double&, T* ) {}
+
+
+template < typename T >
+inline void init_double(double&, double&, double&, double&, double&, double&, double&, double&, double&, double&, double&, T* ) {}
+
+
+template < typename T >
+inline void init_double(double&, double&, double&, double&, double&, double&, double&, double&, double&, double&, double&, double&, T* ) {}
+
+
+template < typename T >
+inline void init_double(double&, double&, double&, double&, double&, double&, double&, double&, double&, double&, double&, double&, double&, T* ) {}
+
+
+
+template < typename ET >
+inline void init_double(double& d0, Lazy_exact_nt<ET>* )
+{d0 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, Lazy_exact_nt<ET>* )
+{d0 = d1 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, double& d3, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = d3 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, double& d3, double& d4, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = d3 = d4 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, double& d3, double& d4, double& d5, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = d3 = d4 = d5 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, double& d3, double& d4, double& d5, double& d6, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = d3 = d4 = d5 = d6 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, double& d3, double& d4, double& d5, double& d6, double& d7, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = d3 = d4 = d5 = d6 = d7 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, double& d3, double& d4, double& d5, double& d6, double& d7, double& d8, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = d3 = d4 = d5 = d6 = d7 = d8 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, double& d3, double& d4, double& d5, double& d6, double& d7, double&d8, double& d9, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = d3 = d4 = d5 = d6 = d7 = d8 = d9 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, double& d3, double& d4, double& d5, double& d6, double& d7, double&d8, double& d9, double& d10, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = d3 = d4 = d5 = d6 = d7 = d8 = d9 = d10 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, double& d3, double& d4, double& d5, double& d6, double& d7, double&d8, double& d9, double& d10, double& d11, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = d3 = d4 = d5 = d6 = d7 = d8 = d9 = d10 = d11 = 0;}
+
+template < typename ET >
+inline void init_double(double& d0, double& d1, double& d2, double& d3, double& d4, double& d5, double& d6, double& d7, double&d8, double& d9, double& d10, double& d11, double& d12, Lazy_exact_nt<ET>* )
+{d0 = d1 = d2 = d3 = d4 = d5 = d6 = d7 = d8 = d9 = d10 = d11 = d12 = 0;}
+
+
 // Auxiliary function to check if static filters can be applied, that is,
 // if to_double() does not add roundoff errors.
 // TODO :
diff --git a/Surface_mesher/test/Surface_mesher/test_c2t3_iterators.cpp b/Surface_mesher/test/Surface_mesher/test_c2t3_iterators.cpp
index b244915b538..6f4ee639dba 100644
--- a/Surface_mesher/test/Surface_mesher/test_c2t3_iterators.cpp
+++ b/Surface_mesher/test/Surface_mesher/test_c2t3_iterators.cpp
@@ -31,7 +31,7 @@ int main(int , char**)
   for(int i = 0; i < 2; ++i)
   {
     Tr::Cell_handle cell;
-    int i1, i2, i3;
+    int i1=0, i2=0, i3=0; // initialize to avoid a g++ -Wall warning
     tr.is_facet(v[i+1], v[(i+2)&3], v[(i+3)&3],
                 cell,
                 i1, i2, i3);