[lmi] [PATCH] Add undisplayable_exception

[Vadim Zeitlin]

 Hello again,

 This is the last patch on which the testing changes depend. I expect it
might be a bit more controversial than the previous ones as it's not really
clear why should there be a special case for this "undisplayable_exception".
And, indeed, during the normal program execution this isn't needed. However
the GUI tests suite depends on being able to catch the exceptions thrown
when a test fails and this wouldn't work if the normal GUI code caught
these exceptions and displayed them to the user and adding a special class
for the sole purpose of allowing to handle it specifically inside
report_exception() is the simplest possibility to do it that I see.

 The patch itself should explain show more clearly how it works:

-- >8 --
diff --git a/handle_exceptions.hpp b/handle_exceptions.hpp
index 2fa9e4b..0205281 100644
--- a/handle_exceptions.hpp
+++ b/handle_exceptions.hpp
@@ -30,6 +30,21 @@

 #include <cstdlib>   // std::exit()
 #include <exception>
+#include <stdexcept>
+
+/// Base class for the exceptions which should not be reported to the user.
+///
+/// Implicitly-declared special member functions do the right thing.
+
+class undisplayable_exception
+    :public std::runtime_error
+{
+  public:
+    explicit undisplayable_exception(std::string const& what)
+        :std::runtime_error(what)
+        {
+        }
+};

 /// This function, of type std::terminate_handler, is intended to be
 /// used as the argument of std::set_terminate().
@@ -67,6 +82,11 @@ inline void lmi_terminate_handler()
 ///  - the safe default action (throwing this exception) was accepted,
 /// in which case it's pointless to repeat the same message.
 ///
+/// Don't handle undisplayable_exception which is the base class for the
+/// exceptions which are not supposed to be ever shown to the user during the
+/// normal program execution -- nor even to arise in this case -- but which may
+/// be generated in special circumstances, e.g. in the testing build.
+///
 /// See
 //   http://article.gmane.org/gmane.comp.gnu.mingw.user/18355
 //     [2005-12-16T09:20:33Z from Greg Chicares]
@@ -85,6 +105,10 @@ inline void report_exception()
     catch(hobsons_choice_exception const&)
         {
         }
+    catch(undisplayable_exception const&)
+        {
+        throw;
+        }
     catch(std::exception const& e)
         {
         safely_show_message(e.what());
-- >8 --

 Possible improvement could consist in choosing an appropriately eldritch
name instead of the current banally descriptive "undisplayable_exception",
but my knowledge of Lovecraftian lore is insufficient to know what would be
most appropriate for a unit testing related class (and has Lovecraft really
plumbed such depths of horror to touch unit testing?).

 Please let me know what do you think about this patch, TIA!
VZ