diff --git a/src/doc/doc/about/drc_ref.xml b/src/doc/doc/about/drc_ref.xml
index 889c3fedcc..203941a1dc 100644
--- a/src/doc/doc/about/drc_ref.xml
+++ b/src/doc/doc/about/drc_ref.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE language SYSTEM "klayout_doc.dtd">
 
-<!-- generated by /home/matthias/klayout/0.28/scripts/drc_lvs_doc/extract_doc.rb  -->
+<!-- generated by /home/matthias/klayout/master/scripts/drc_lvs_doc/extract_doc.rb  -->
 <!-- DO NOT EDIT! -->
 
 <doc>
diff --git a/src/doc/doc/about/drc_ref_drc.xml b/src/doc/doc/about/drc_ref_drc.xml
index 7ee678ecab..7f121c94ad 100644
--- a/src/doc/doc/about/drc_ref_drc.xml
+++ b/src/doc/doc/about/drc_ref_drc.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE language SYSTEM "klayout_doc.dtd">
 
-<!-- generated by /home/matthias/klayout/0.28/scripts/drc_lvs_doc/extract_doc.rb  -->
+<!-- generated by /home/matthias/klayout/master/scripts/drc_lvs_doc/extract_doc.rb  -->
 <!-- DO NOT EDIT! -->
 
 <doc>
@@ -358,7 +358,7 @@ The plain function is equivalent to "primary.bbox_width".
 This method acts on edge expressions and delivers a specific part of each edge.
 See <a href="/about/drc_ref_layer.xml#centers">layer#centers</a> for details about this functionality.
 </p>
-<a name="corners"/><h2>"corners" - Applies smoothing</h2>
+<a name="corners"/><h2>"corners" - Selects corners of polygons</h2>
 <keyword name="corners"/>
 <p>Usage:</p>
 <ul>
@@ -369,8 +369,10 @@ See <a href="/about/drc_ref_layer.xml#centers">layer#centers</a> for details abo
 <p>
 This operation acts on polygons and selects the corners of the polygons.
 It can be put into a condition to select corners by their angles. The angle of
-a corner is positive for a turn to the left if walking a polygon counterclockwise
-and negative for the turn to the right. Angles take values between -180 and 180 degree.
+a corner is positive for a turn to the left if walking a polygon clockwise
+and negative for the turn to the right. Hence positive angles indicate concave
+(inner) corners, negative ones indicate convex (outer) corners.
+Angles take values between -180 and 180 degree.
 </p><p>
 When using "as_dots" for the argument, the operation will return single-point edges at
 the selected corners. With "as_boxes" (the default), small (2x2 DBU) rectangles will be
@@ -386,8 +388,8 @@ out = in.drc(primary.corners)    # equivalent
 The following example selects all inner corners:
 </p><p>
 <pre>
-out = in.drc(corners &lt; 0)
-out = in.drc(primary.corners &lt; 0)    # equivalent
+out = in.drc(corners &gt; 0)
+out = in.drc(primary.corners &gt; 0)    # equivalent
 </pre>
 </p><p>
 The "corners" method is available as a plain function or as a method on <a href="/about/drc_ref_drc.xml">DRC</a> expressions.
diff --git a/src/doc/doc/about/drc_ref_global.xml b/src/doc/doc/about/drc_ref_global.xml
index 7e8b6ba825..6706516286 100644
--- a/src/doc/doc/about/drc_ref_global.xml
+++ b/src/doc/doc/about/drc_ref_global.xml
@@ -1,17 +1,12 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE language SYSTEM "klayout_doc.dtd">
 
-<!-- generated by /home/matthias/klayout/0.28/scripts/drc_lvs_doc/extract_doc.rb  -->
+<!-- generated by /home/matthias/klayout/master/scripts/drc_lvs_doc/extract_doc.rb  -->
 <!-- DO NOT EDIT! -->
 
 <doc>
 <title>DRC Reference: Global Functions</title>
 <keyword name="global"/>
-<p>
-Some functions are available on global level and can be used without any object.
-Most of them are convenience functions that basically act on some default object
-or provide function-like alternatives for the methods.
-</p>
 <h2-index/>
 <a name="angle"/><h2>"angle" - In universal DRC context: selects edges based on their orientation</h2>
 <keyword name="angle"/>
diff --git a/src/doc/doc/about/drc_ref_layer.xml b/src/doc/doc/about/drc_ref_layer.xml
index ce8c3aa4aa..35af6a5b49 100644
--- a/src/doc/doc/about/drc_ref_layer.xml
+++ b/src/doc/doc/about/drc_ref_layer.xml
@@ -1,15 +1,12 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE language SYSTEM "klayout_doc.dtd">
 
-<!-- generated by /home/matthias/klayout/0.28/scripts/drc_lvs_doc/extract_doc.rb  -->
+<!-- generated by /home/matthias/klayout/master/scripts/drc_lvs_doc/extract_doc.rb  -->
 <!-- DO NOT EDIT! -->
 
 <doc>
 <title>DRC Reference: Layer Object</title>
 <keyword name="Layer"/>
-<p>
-The layer object represents a collection of polygons, edges or edge pairs.
-</p>
 <h2-index/>
 <a name="&amp;"/><h2>"&amp;" - Boolean AND operation</h2>
 <keyword name="&amp;"/>
@@ -268,7 +265,7 @@ deliver objects that can be converted into polygons. Such objects are of class <
 This method produces markers on the corners of the polygons. An angle criterion can be given which
 selects corners based on the angle of the connecting edges. Positive angles indicate a left turn
 while negative angles indicate a right turn. Since polygons are oriented clockwise, positive angles
-indicate concave corners while negative ones indicate convex corners.
+indicate concave (inner) corners while negative ones indicate convex (outer) corners
 </p><p>
 The markers generated can be point-like edges or small 2x2 DBU boxes. The latter is the default.
 </p><p>
diff --git a/src/doc/doc/about/drc_ref_netter.xml b/src/doc/doc/about/drc_ref_netter.xml
index f031499446..8fd41f6f50 100644
--- a/src/doc/doc/about/drc_ref_netter.xml
+++ b/src/doc/doc/about/drc_ref_netter.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE language SYSTEM "klayout_doc.dtd">
 
-<!-- generated by /home/matthias/klayout/0.28/scripts/drc_lvs_doc/extract_doc.rb  -->
+<!-- generated by /home/matthias/klayout/master/scripts/drc_lvs_doc/extract_doc.rb  -->
 <!-- DO NOT EDIT! -->
 
 <doc>
diff --git a/src/doc/doc/about/drc_ref_source.xml b/src/doc/doc/about/drc_ref_source.xml
index a9ab3eaabd..74d119bcb1 100644
--- a/src/doc/doc/about/drc_ref_source.xml
+++ b/src/doc/doc/about/drc_ref_source.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE language SYSTEM "klayout_doc.dtd">
 
-<!-- generated by /home/matthias/klayout/0.28/scripts/drc_lvs_doc/extract_doc.rb  -->
+<!-- generated by /home/matthias/klayout/master/scripts/drc_lvs_doc/extract_doc.rb  -->
 <!-- DO NOT EDIT! -->
 
 <doc>
diff --git a/src/doc/doc/about/lvs_ref.xml b/src/doc/doc/about/lvs_ref.xml
index 4a38dd6db2..58168f012e 100644
--- a/src/doc/doc/about/lvs_ref.xml
+++ b/src/doc/doc/about/lvs_ref.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE language SYSTEM "klayout_doc.dtd">
 
-<!-- generated by /home/matthias/klayout/0.28/scripts/drc_lvs_doc/extract_doc.rb  -->
+<!-- generated by /home/matthias/klayout/master/scripts/drc_lvs_doc/extract_doc.rb  -->
 <!-- DO NOT EDIT! -->
 
 <doc>
diff --git a/src/doc/doc/about/lvs_ref_global.xml b/src/doc/doc/about/lvs_ref_global.xml
index c262d68153..c1d2ad9149 100644
--- a/src/doc/doc/about/lvs_ref_global.xml
+++ b/src/doc/doc/about/lvs_ref_global.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE language SYSTEM "klayout_doc.dtd">
 
-<!-- generated by /home/matthias/klayout/0.28/scripts/drc_lvs_doc/extract_doc.rb  -->
+<!-- generated by /home/matthias/klayout/master/scripts/drc_lvs_doc/extract_doc.rb  -->
 <!-- DO NOT EDIT! -->
 
 <doc>
diff --git a/src/doc/doc/about/lvs_ref_netter.xml b/src/doc/doc/about/lvs_ref_netter.xml
index f5f8512039..9feef786f6 100644
--- a/src/doc/doc/about/lvs_ref_netter.xml
+++ b/src/doc/doc/about/lvs_ref_netter.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE language SYSTEM "klayout_doc.dtd">
 
-<!-- generated by /home/matthias/klayout/0.28/scripts/drc_lvs_doc/extract_doc.rb  -->
+<!-- generated by /home/matthias/klayout/master/scripts/drc_lvs_doc/extract_doc.rb  -->
 <!-- DO NOT EDIT! -->
 
 <doc>
diff --git a/src/drc/drc/built-in-macros/_drc_complex_ops.rb b/src/drc/drc/built-in-macros/_drc_complex_ops.rb
index c3674e3d2e..aa9e9e7d32 100644
--- a/src/drc/drc/built-in-macros/_drc_complex_ops.rb
+++ b/src/drc/drc/built-in-macros/_drc_complex_ops.rb
@@ -756,15 +756,17 @@ def smoothed(d, keep_hv = false)
   
   # %DRC%
   # @name corners
-  # @brief Applies smoothing
+  # @brief Selects corners of polygons
   # @synopsis expression.corners
   # @synopsis expression.corners(as_dots)
   # @synopsis expression.corners(as_boxes)
   #
   # This operation acts on polygons and selects the corners of the polygons.
   # It can be put into a condition to select corners by their angles. The angle of
-  # a corner is positive for a turn to the left if walking a polygon counterclockwise
-  # and negative for the turn to the right. Angles take values between -180 and 180 degree.
+  # a corner is positive for a turn to the left if walking a polygon clockwise
+  # and negative for the turn to the right. Hence positive angles indicate concave
+  # (inner) corners, negative ones indicate convex (outer) corners.
+  # Angles take values between -180 and 180 degree.
   #
   # When using "as_dots" for the argument, the operation will return single-point edges at
   # the selected corners. With "as_boxes" (the default), small (2x2 DBU) rectangles will be
@@ -780,8 +782,8 @@ def smoothed(d, keep_hv = false)
   # The following example selects all inner corners:
   #
   # @code
-  # out = in.drc(corners < 0)
-  # out = in.drc(primary.corners < 0)    # equivalent
+  # out = in.drc(corners > 0)
+  # out = in.drc(primary.corners > 0)    # equivalent
   # @/code
   #
   # The "corners" method is available as a plain function or as a method on \DRC# expressions.
diff --git a/src/drc/drc/built-in-macros/_drc_layer.rb b/src/drc/drc/built-in-macros/_drc_layer.rb
index ffa80b9433..24c2cbb2e0 100644
--- a/src/drc/drc/built-in-macros/_drc_layer.rb
+++ b/src/drc/drc/built-in-macros/_drc_layer.rb
@@ -1232,7 +1232,7 @@ def _texts_impl(invert, *args)
     # This method produces markers on the corners of the polygons. An angle criterion can be given which
     # selects corners based on the angle of the connecting edges. Positive angles indicate a left turn
     # while negative angles indicate a right turn. Since polygons are oriented clockwise, positive angles
-    # indicate concave corners while negative ones indicate convex corners.
+    # indicate concave (inner) corners while negative ones indicate convex (outer) corners
     # 
     # The markers generated can be point-like edges or small 2x2 DBU boxes. The latter is the default.
     # 
diff --git a/src/plugins/streamers/lefdef/db_plugin/dbLEFDEFImporter.cc b/src/plugins/streamers/lefdef/db_plugin/dbLEFDEFImporter.cc
index 5f03940572..803cca4566 100644
--- a/src/plugins/streamers/lefdef/db_plugin/dbLEFDEFImporter.cc
+++ b/src/plugins/streamers/lefdef/db_plugin/dbLEFDEFImporter.cc
@@ -1117,7 +1117,7 @@ LEFDEFReaderState::read_single_map_file (const std::string &path, std::map<std::
       size_t max_purpose_str = 15;
 
       if (! ex.try_read_word (w1) || ! ex.try_read_word (w2, "._$,/:") || ! try_read_layers (ex, layers) || ! try_read_layers (ex, datatypes)) {
-        tl::warn << tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d not understood - skipped")), path, ts.line_number ());
+        common_reader_warn (tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d not understood - skipped")), path, ts.line_number ()));
         continue;
       }
 
@@ -1143,7 +1143,7 @@ LEFDEFReaderState::read_single_map_file (const std::string &path, std::map<std::
           name = "REGIONS_NONE";
           lp = RegionsNone;
         } else if (w2 != "ALL") {
-          tl::warn << tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d - ignoring unknowns REGION purpose %s (use FENCE, GUIDE or ALL)")), path, ts.line_number (), w2);
+          common_reader_warn (tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d - ignoring unknowns REGION purpose %s (use FENCE, GUIDE or ALL)")), path, ts.line_number (), w2));
         }
 
         for (std::vector<int>::const_iterator l = layers.begin (); l != layers.end (); ++l) {
@@ -1176,7 +1176,7 @@ LEFDEFReaderState::read_single_map_file (const std::string &path, std::map<std::
 
           if (*p == "DIEAREA" || *p == "ALL" || *p == "COMP") {
 
-            tl::warn << tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d: NAME record ignored for entity: %s")), path, ts.line_number (), *p);
+            common_reader_warn (tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d: NAME record ignored for entity: %s")), path, ts.line_number (), *p));
 
           } else {
 
@@ -1193,7 +1193,7 @@ LEFDEFReaderState::read_single_map_file (const std::string &path, std::map<std::
               if (label_purpose == Pins || label_purpose == LEFPins) {
                 layer_defs.push_back (std::make_pair (lp.front (), label_purpose == Pins ? Label : LEFLabel));
               } else {
-                tl::warn << tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d: NAME record ignored for purpose: %s")), path, ts.line_number (), purpose_to_name (label_purpose));
+                common_reader_warn (tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d: NAME record ignored for purpose: %s")), path, ts.line_number (), purpose_to_name (label_purpose)));
               }
 
             } else {
@@ -1226,7 +1226,7 @@ LEFDEFReaderState::read_single_map_file (const std::string &path, std::map<std::
       } else if (w1 == "COMP") {
 
         //  ignore "COMP (ALL) ..."
-        tl::warn << tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d: COMP entry ignored")), path, ts.line_number ());
+        common_reader_warn (tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d: COMP entry ignored")), path, ts.line_number ()));
 
       } else {
 
@@ -1261,7 +1261,7 @@ LEFDEFReaderState::read_single_map_file (const std::string &path, std::map<std::
               if (ex.test (":VOLTAGE:")) {
                 double f = 0.0;
                 ex.read (f);
-                tl::warn << tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d: NET voltage constraint ignored for layer %s")), path, ts.line_number (), w1);
+                common_reader_warn (tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d: NET voltage constraint ignored for layer %s")), path, ts.line_number (), w1));
               }
 
             } else if (i->second == ViaGeometry) {
@@ -1284,7 +1284,7 @@ LEFDEFReaderState::read_single_map_file (const std::string &path, std::map<std::
 
           if (i == purpose_translation.end ()) {
 
-            tl::warn << tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d: purpose %s ignored for layer %s")), path, ts.line_number (), ps, w1);
+            common_reader_warn (tl::sprintf (tl::to_string (tr ("Reading layer map file %s, line %d: purpose %s ignored for layer %s")), path, ts.line_number (), ps, w1));
 
           } else if (i->second == All) {
 
@@ -1364,21 +1364,22 @@ LEFDEFReaderState::open_layer (db::Layout &layout, const std::string &n, LayerPu
     m_layers.insert (std::make_pair (std::make_pair (n, LayerDetailsKey (purpose, mask)), ll));
 
     if (ll.empty () && ! has_fallback (purpose)) {
+      std::string msg;
       if (n.empty ()) {
-        tl::warn << tl::to_string (tr ("No mapping for purpose")) << " '" << purpose_to_name (purpose) << "'" << tl::noendl;
+        msg = tl::to_string (tr ("No mapping for purpose")) + " '" + purpose_to_name (purpose) + "'";
       } else {
-        tl::warn << tl::to_string (tr ("No mapping for layer")) << " '" << n << "', purpose '" << purpose_to_name (purpose) << "'" << tl::noendl;
+        msg = tl::to_string (tr ("No mapping for layer")) + " '" + n + "', purpose '" + purpose_to_name (purpose) + "'";
       }
       if (mask > 0) {
-        tl::warn << tl::to_string (tr (" Mask ")) << mask << tl::noendl;
+        msg += tl::to_string (tr (" Mask ")) + tl::to_string (mask);
       }
 //  not printing via size - too confusing?
 #if 0
       if (via_size != db::DVector ()) {
-        tl::warn << tl::to_string (tr (" Via size ")) << via_size.to_string () << tl::noendl;
+        msg += tl::to_string (tr (" Via size ")) + via_size.to_string ();
       }
 #endif
-      tl::warn << tl::to_string (tr (" - layer is ignored"));
+      common_reader_warn (msg + tl::to_string (tr (" - layer is ignored")));
     }
 
     return ll;