central classification of 'unsafe' exceptions

3 files changed, 50 insertions, 0 deletions

diff --git a/vespalib/src/tests/exception_classes/exception_classes_test.cpp b/vespalib/src/tests/exception_classes/exception_classes_test.cpp
index 2741fe20161..ffe0f21ceb8 100644
--- a/vespalib/src/tests/exception_classes/exception_classes_test.cpp
+++ b/vespalib/src/tests/exception_classes/exception_classes_test.cpp
@@ -47,4 +47,23 @@ TEST("test that OOMException carries message forward.") {
     EXPECT_TRUE(caught);
 }
 
+TEST("require that rethrow_if_unsafe will rethrow unsafe exception") {
+    try {
+        try {
+            throw OOMException("my message");
+        } catch (const std::exception &e) {
+            rethrow_if_unsafe(e);
+            TEST_ERROR("should not be reached");
+        }
+    } catch (const OOMException &) {}
+}
+
+TEST("require that rethrow_if_unsafe will not rethrow safe exception") {
+    try {
+        throw IllegalArgumentException("my message");
+    } catch (const std::exception &e) {
+        rethrow_if_unsafe(e);
+    }
+}
+
 TEST_MAIN() { TEST_RUN_ALL(); }
diff --git a/vespalib/src/vespa/vespalib/util/exceptions.cpp b/vespalib/src/vespa/vespalib/util/exceptions.cpp
index 8fb50a9403c..2c21ab8bcea 100644
--- a/vespalib/src/vespa/vespalib/util/exceptions.cpp
+++ b/vespalib/src/vespa/vespalib/util/exceptions.cpp
@@ -186,4 +186,18 @@ IoException::getErrorType(int error) {
     }
 }
 
+template <typename T>
+bool check_type(const std::exception &e) {
+    return (dynamic_cast<const T *>(&e) != nullptr);
+}
+
+void rethrow_if_unsafe(const std::exception &e) {
+    if (check_type<std::bad_alloc>(e) ||
+        check_type<OOMException>(e) ||
+        check_type<FatalException>(e))
+    {
+        throw;
+    }
+}
+
 } // vespalib
diff --git a/vespalib/src/vespa/vespalib/util/exceptions.h b/vespalib/src/vespa/vespalib/util/exceptions.h
index c1afaf0122a..8c470d25a5b 100644
--- a/vespalib/src/vespa/vespalib/util/exceptions.h
+++ b/vespalib/src/vespa/vespalib/util/exceptions.h
@@ -154,5 +154,22 @@ private:
     std::terminate_handler _oldTerminate;
 };
 
+/**
+ * NOTE: This function must only be called from within a catch block,
+ * and the parameter must reference the caught exception.
+ * 
+ * Based on the run-time type of the exception, determine if it is
+ * safe to handle this exception and continue normal program
+ * operation. If the exception is considered safe, no additional
+ * action is taken. If the exception is considered unsafe, it will be
+ * re-thrown.
+ *
+ * Unsafe exceptions fall under two categories; exceptions that are
+ * specifically designed to end program execution and exceptions that
+ * have an elevated chance of causing issues when being thrown across
+ * code that is not completely exception safe.
+ **/
+void rethrow_if_unsafe(const std::exception &e);
+
 }