diff --git a/src/db/db/dbEdges.h b/src/db/db/dbEdges.h
index 68fe606d2..17788cde3 100644
--- a/src/db/db/dbEdges.h
+++ b/src/db/db/dbEdges.h
@@ -229,8 +229,11 @@ private:
    *  @brief ctor from a recursive shape iterator
    */
   EdgesIterator (const db::RecursiveShapeIterator &iter, const db::ICplxTrans &trans)
-    : m_rec_iter (iter), m_iter_trans (trans)
-  { 
+    : m_rec_iter (iter), m_iter_trans (trans), m_from (), m_to ()
+  {
+    //  NOTE: the following initialization appears to be required on some compilers
+    //  (specifically MacOS/clang) to ensure the proper initialization of the iterators
+    m_from = m_to;
     set ();
   }
 
diff --git a/src/db/unit_tests/dbCell.cc b/src/db/unit_tests/dbCell.cc
index 4461dd7ae..d4f6c9658 100644
--- a/src/db/unit_tests/dbCell.cc
+++ b/src/db/unit_tests/dbCell.cc
@@ -570,13 +570,13 @@ TEST(2)
 
   }
 
-  c0.erase (i4);
-  EXPECT_EQ (c2s_unsorted(c0), "5[r0 *1 0,0]#2,3[r0 *1 0,0]#13");
-  EXPECT_EQ (c0.cell_instances (), size_t (2));
   c0.erase (i5);
+  EXPECT_EQ (c2s_unsorted(c0), "5[r0 *1 0,0]#2,1[r0 *1 0,0]#1");
+  EXPECT_EQ (c0.cell_instances (), size_t (2));
+  c0.erase (i4);
   EXPECT_EQ (c2s_unsorted(c0), "5[r0 *1 0,0]#2");
   EXPECT_EQ (c0.cell_instances (), size_t (1));
-  // not yet: EXPECT_EQ (c0.empty (), false);
+  //  Not yet: EXPECT_EQ (c0.empty (), false);
 
   //  note: double delete is not supported in non-editable mode 
   if (db::default_editable_mode ()) {
@@ -608,7 +608,7 @@ TEST(2)
   c0.erase (i3);
   EXPECT_EQ (c2s_unsorted(c0), "");
   EXPECT_EQ (c0.cell_instances (), size_t (0));
-  // not yet: EXPECT_EQ (c0.empty (), true);
+  //  Not yet: EXPECT_EQ (c0.empty (), true);
 }
 
 TEST(3) 
diff --git a/src/gsi/gsi/gsiCallback.h b/src/gsi/gsi/gsiCallback.h
index 21a78ab62..f173bf0e7 100644
--- a/src/gsi/gsi/gsiCallback.h
+++ b/src/gsi/gsi/gsiCallback.h
@@ -34,7 +34,7 @@ namespace gsi
  *
  *  This class is specialized to implement the actual call process later.
  */
-struct Callee
+struct GSI_PUBLIC Callee
   : public tl::Object
 {
   Callee () { }
@@ -49,7 +49,7 @@ struct Callee
  *  This object holds informations about the actual implementation of the callback 
  *  on the scripting client's side.
  */
-struct Callback 
+struct Callback
 {
   Callback () 
     : id (-1), callee (0), argsize (0), retsize (0)
diff --git a/src/gsi/gsi/gsiDeclBasic.h b/src/gsi/gsi/gsiDeclBasic.h
index 7bafa8000..b77d46fda 100644
--- a/src/gsi/gsi/gsiDeclBasic.h
+++ b/src/gsi/gsi/gsiDeclBasic.h
@@ -37,7 +37,7 @@ namespace gsi
 /**
  *  @brief Provides a basic implementation for a "boxed" plain value using a Variant as the basic type
  */
-class Value
+class GSI_PUBLIC Value
 {
 public:
   /**
diff --git a/src/lay/lay/laySystemPaths.cc b/src/lay/lay/laySystemPaths.cc
index 6e458716c..2f5645c32 100644
--- a/src/lay/lay/laySystemPaths.cc
+++ b/src/lay/lay/laySystemPaths.cc
@@ -30,6 +30,9 @@
 
 #ifdef _WIN32
 #  include <windows.h>
+#elif __APPLE__
+#  include <libproc.h>
+#  include <unistd.h>
 #else
 #  include <unistd.h>
 #endif
@@ -79,6 +82,15 @@ get_inst_path_internal ()
     return tl::to_string (fi.absolutePath ());
   } 
 
+#elif __APPLE__
+
+  char buffer[PROC_PIDPATHINFO_MAXSIZE];
+  int ret = proc_pidpath (getpid (), buffer, sizeof (buffer));
+  if (ret > 0) {
+    //  TODO: does this correctly translate paths? (MacOS uses UTF-8 encoding with D-like normalization)
+    return tl::to_string (QFileInfo (QString::fromUtf8 (buffer)).absolutePath ());
+  }
+
 #else 
     
   QFileInfo proc_exe (tl::to_qstring (tl::sprintf ("/proc/%d/exe", getpid ())));
diff --git a/src/tl/tl/tlException.h b/src/tl/tl/tlException.h
index 306af3c95..0b1baafc0 100644
--- a/src/tl/tl/tlException.h
+++ b/src/tl/tl/tlException.h
@@ -137,7 +137,7 @@ private:
  *  @brief A "neutral" exception thrown to terminate some operation
  *  This exception is not shown.
  */
-struct CancelException
+struct TL_PUBLIC CancelException
   : public Exception
 {
   CancelException ()
@@ -148,7 +148,7 @@ struct CancelException
 /**
  *  @brief A special "internal" exception class used by tl_assert
  */
-struct InternalException
+struct TL_PUBLIC InternalException
   : public Exception
 {
   InternalException (const char *file, int line, const char *cond)
diff --git a/src/unit_tests/unit_test_main.cc b/src/unit_tests/unit_test_main.cc
index 1d0bc6b79..80d64c7b5 100644
--- a/src/unit_tests/unit_test_main.cc
+++ b/src/unit_tests/unit_test_main.cc
@@ -365,6 +365,10 @@ main_cont (int argc, char **argv)
 
     }
 
+    if (! tl::TestRegistrar::instance()) {
+      throw tl::Exception ("No test libraries found - make sure, the *.ut files are next to the ut_runner executable.");
+    }
+
     //  No side effects
     lay::set_klayout_path (std::vector<std::string> ());
 
diff --git a/src/unit_tests/unit_tests.pro b/src/unit_tests/unit_tests.pro
index 7e45e19fd..68df3dffc 100644
--- a/src/unit_tests/unit_tests.pro
+++ b/src/unit_tests/unit_tests.pro
@@ -6,6 +6,11 @@ include($$PWD/../with_all_libs.pri)
 
 TEMPLATE = app
 
+# Don't build the ut_runner app as ordinary command line tool on MacOS
+mac {
+  CONFIG -= app_bundle
+}
+
 TARGET = ut_runner
 
 SOURCES = \