From 7a7fd87b34a98002c2de4bcf64c9afdfb203e15d Mon Sep 17 00:00:00 2001
From: Linas Vepstas <linasvepstas@gmail.com>
Date: Tue, 23 Dec 2014 12:22:40 -0600
Subject: [PATCH] Convert c++ exceptions into scheme exceptions

---
 opencog/guile/SchemePrimitive.cc    | 23 +++++++++++++++--------
 tests/scm/SCMPrimitiveUTest.cxxtest |  2 +-
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/opencog/guile/SchemePrimitive.cc b/opencog/guile/SchemePrimitive.cc
index a8b72b47d3c..8f3421acfed 100644
--- a/opencog/guile/SchemePrimitive.cc
+++ b/opencog/guile/SchemePrimitive.cc
@@ -111,7 +111,9 @@ SCM PrimitiveEnviron::do_call(SCM sfe, SCM arglist)
 
 	// If the C++ code throws any exceptions, and no one else
 	// has caught them, then we have to catch them, and print 
-	// an error message to the shell.
+	// an error message to the shell. Actually, we'll be
+	// quasi-nice about this, and convert the C++ exception
+	// into a scheme exception.
 	try
 	{
 		rc = fe->invoke(arglist);
@@ -119,14 +121,19 @@ SCM PrimitiveEnviron::do_call(SCM sfe, SCM arglist)
 	catch (const std::exception& ex)
 	{
 		const char *msg = ex.what();
+
+		// Should we even bother to log this?
+		logger().info("Guile caught C++ exception: %s", msg);
+
 		// scm_misc_error(fe->get_name(), msg, SCM_EOL);
-		scm_error_scm(
-			scm_from_locale_symbol("C++ exception"),
-			scm_from_locale_string(fe->get_name()),
-			scm_from_locale_string(msg),
-			SCM_EOL,
-			SCM_EOL);
-		logger().error("Guile caught C++ exception: %s", msg);
+		scm_throw(
+			scm_from_locale_symbol(msg),
+			scm_cons(
+				scm_from_locale_string("C++ exception"),
+				scm_cons(
+					scm_from_locale_string(fe->get_name()),
+					SCM_EOL)));
+		// Hmm. scm_throw never returns.
 	}
 	catch (...)
 	{
diff --git a/tests/scm/SCMPrimitiveUTest.cxxtest b/tests/scm/SCMPrimitiveUTest.cxxtest
index 9b4ca694841..eb11ffec35f 100644
--- a/tests/scm/SCMPrimitiveUTest.cxxtest
+++ b/tests/scm/SCMPrimitiveUTest.cxxtest
@@ -92,7 +92,7 @@ class MyExampleClass
 		// Throw exception on purpose
 		Handle my_other_func(Handle h)
 		{
-			throw (RuntimeException(TRACE_INFO, "Don't panic!! Threw exception %d on purpose.", id));
+			throw (InvalidParamException(TRACE_INFO, "Don't panic!! Threw exception %d on purpose.", id));
 			return Handle::UNDEFINED;
 		}
 };