--- a/liboctave/util/lo-array-errwarn.cc	Thu Jan 23 16:19:33 2020 -0500
+++ b/liboctave/util/lo-array-errwarn.cc	Thu Jan 23 16:22:27 2020 -0500
@@ -128,6 +128,13 @@
     return expression () + ": " + details ();
   }
 
+  const char * index_exception::what (void) const noexcept
+  {
+    std::string tmp = message ();
+
+    return tmp.c_str ();
+   }
+
   // Show the expression that caused the error, e.g.,  "A(-1,_)",
   // "A(0+1i)", "A(_,3)".  Show how many indices come before/after the
   // offending one, e.g., (<error>), (<error>,_), or (_,<error>,...[x5]...)

--- a/liboctave/util/lo-array-errwarn.h	Thu Jan 23 16:19:33 2020 -0500
+++ b/liboctave/util/lo-array-errwarn.h	Thu Jan 23 16:22:27 2020 -0500
@@ -52,8 +52,8 @@
 
     ~index_exception (void) = default;
 
-    // Erroneous index value.  Called in what, and by external code
-    // (e.g., nth_element) to make a custom error message.
+    // Erroneous index value.  Called in message method and by external
+    // code (e.g., nth_element) to make a custom error message.
     std::string idx (void) const { return m_index; }
 
     // details set by subclass.
@@ -64,6 +64,9 @@
 
     virtual std::string message (void) const;
 
+    // Provided for std::exception interface.
+    const char * what (void) const noexcept;
+
     // Position of error: dimension in error, and number of dimensions.
     void set_pos (octave_idx_type nd_arg, octave_idx_type dim_arg)
     {

--- a/liboctave/util/quit.h	Thu Jan 23 16:19:33 2020 -0500
+++ b/liboctave/util/quit.h	Thu Jan 23 16:22:27 2020 -0500
@@ -33,6 +33,7 @@
 #  include <csignal>
 #  include <iosfwd>
 #  include <list>
+#  include <stdexcept>
 #  include <string>
 extern "C" {
 #else
@@ -88,8 +89,7 @@
             && a.column () == b.column ());
   }
 
-  class
-  execution_exception
+  class execution_exception : std::runtime_error
   {
   public:
 
@@ -99,8 +99,8 @@
                          const std::string& id = "",
                          const std::string& message = "unspecified error",
                          const stack_info_type& stack_info = stack_info_type ())
-      : m_err_type (err_type), m_id (id), m_message (message),
-        m_stack_info (stack_info)
+      : runtime_error (message), m_err_type (err_type), m_id (id),
+        m_message (message), m_stack_info (stack_info)
     { }
 
     execution_exception (const execution_exception&) = default;
@@ -132,6 +132,9 @@
 
     virtual std::string message (void) const { return m_message; }
 
+    // Provided for std::exception interface.
+    const char * what (void) const noexcept { return m_message.c_str (); }
+
     virtual stack_info_type stack_info (void) const
     {
       return m_stack_info;
@@ -155,8 +158,9 @@
     stack_info_type m_stack_info;
   };
 
-  class
-  exit_exception
+  // Intentionally not derived from std::exception.
+
+  class exit_exception
   {
   public:
 
@@ -192,8 +196,9 @@
     bool m_safe_to_return;
   };
 
-  class
-  interrupt_exception
+  // Intentionally not derived from std::exception.
+
+  class interrupt_exception
   {
   };
 }