diff --git a/vcg/complex/algorithms/local_optimization/quad_diag_collapse.h b/vcg/complex/algorithms/local_optimization/quad_diag_collapse.h
index 94d65353..f2dea23a 100755
--- a/vcg/complex/algorithms/local_optimization/quad_diag_collapse.h
+++ b/vcg/complex/algorithms/local_optimization/quad_diag_collapse.h
@@ -358,9 +358,12 @@ namespace vcg{
 
             virtual const char *Info(MeshType &m)
             {
-                static char buf[60];
-                sprintf(buf,"(%d - %d) %g\n", hp->HVp()-&m.vert[0], hp->HNp()->HNp()->HVp()-&m.vert[0], -_priority);
-                return buf;
+                static std::string msg;
+                msg =
+                    "(" + std::to_string(hp->HVp()-&m.vert[0]) +
+                    " - " + std::to_string(hp->HNp()->HNp()->HVp()-&m.vert[0]) +
+                    ") " + std::to_string(-_priority) + "\n";
+                return msg.c_str();
             }
 
             /*!
diff --git a/vcg/complex/algorithms/local_optimization/tri_edge_collapse.h b/vcg/complex/algorithms/local_optimization/tri_edge_collapse.h
index 309210da..0a4a8693 100644
--- a/vcg/complex/algorithms/local_optimization/tri_edge_collapse.h
+++ b/vcg/complex/algorithms/local_optimization/tri_edge_collapse.h
@@ -115,9 +115,12 @@ public:
 
   virtual const char *Info(TriMeshType &m) {
     mt = &m;
-    static char buf[60];
-      sprintf(buf,"%i -> %i %g\n", int(pos.V(0)-&m.vert[0]), int(pos.V(1)-&m.vert[0]),-_priority);
-   return buf;
+    static std::string msg;
+    msg =
+        std::to_string(int(pos.V(0)-&m.vert[0])) + " -> " +
+        std::to_string(int(pos.V(1)-&m.vert[0])) +
+        " " + std::to_string(-_priority) + "\n";
+    return msg.c_str();
   }
 
   inline void Execute(TriMeshType &m, BaseParameterClass *)
diff --git a/vcg/complex/algorithms/local_optimization/tri_edge_flip.h b/vcg/complex/algorithms/local_optimization/tri_edge_flip.h
index 29f26b5f..2ad4d64e 100644
--- a/vcg/complex/algorithms/local_optimization/tri_edge_flip.h
+++ b/vcg/complex/algorithms/local_optimization/tri_edge_flip.h
@@ -283,9 +283,12 @@ public:
      */
     const char* Info(TRIMESH_TYPE &m)
     {
-        static char dump[60];
-        sprintf(dump,"%zu -> %zu %g\n", tri::Index(m,_pos.F()->V(0)), tri::Index(m,_pos.F()->V(1)),-_priority);
-        return dump;
+        static std::string msg;
+        msg =
+            std::to_string(tri::Index(m,_pos.F()->V(0))) + " -> " +
+            std::to_string(tri::Index(m,_pos.F()->V(1))) +
+            " " + std::to_string(-_priority) + "\n";
+        return msg.c_str();
     }
 
     /*!