added UnwindMessage/unwind_msg

6 files changed, 118 insertions, 0 deletions

diff --git a/vespalib/CMakeLists.txt b/vespalib/CMakeLists.txt
index 5c0574aad8a..9e06bb152fd 100644
--- a/vespalib/CMakeLists.txt
+++ b/vespalib/CMakeLists.txt
@@ -133,6 +133,7 @@ vespa_define_module(
     src/tests/tutorial/simple
     src/tests/tutorial/threads
     src/tests/typify
+    src/tests/unwind_message
     src/tests/util/bfloat16
     src/tests/util/file_area_freelist
     src/tests/util/generationhandler
diff --git a/vespalib/src/tests/unwind_message/CMakeLists.txt b/vespalib/src/tests/unwind_message/CMakeLists.txt
new file mode 100644
index 00000000000..92295ada035
--- /dev/null
+++ b/vespalib/src/tests/unwind_message/CMakeLists.txt
@@ -0,0 +1,9 @@
+# Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+vespa_add_executable(vespalib_unwind_message_test_app TEST
+    SOURCES
+    unwind_message_test.cpp
+    DEPENDS
+    vespalib
+    GTest::GTest
+)
+vespa_add_test(NAME vespalib_unwind_message_test_app COMMAND vespalib_unwind_message_test_app)
diff --git a/vespalib/src/tests/unwind_message/unwind_message_test.cpp b/vespalib/src/tests/unwind_message/unwind_message_test.cpp
new file mode 100644
index 00000000000..53a7bf26c90
--- /dev/null
+++ b/vespalib/src/tests/unwind_message/unwind_message_test.cpp
@@ -0,0 +1,37 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include <vespa/vespalib/util/unwind_message.h>
+#include <vespa/vespalib/gtest/gtest.h>
+#include <stdexcept>
+
+using vespalib::unwind_msg;
+using vespalib::UnwindMessage;
+
+//-----------------------------------------------------------------------------
+
+struct MyObj {
+    UnwindMessage msg1 = UnwindMessage("this SHOULD be printed (1/2)");
+    UnwindMessage msg2 = UnwindMessage("this should NOT be printed (1)");
+    ~MyObj() {
+        EXPECT_EQ(std::uncaught_exceptions(), 1);
+        auto not_printed_1 = std::move(msg2);
+        auto not_printed_2 = unwind_msg("this should NOT be printed (2)");
+    }
+};
+
+TEST(UnwindMessageTest, unwind_messages_are_printed_when_appropriate) {
+    using E = std::invalid_argument;
+    auto not_printed_3 = unwind_msg("this should NOT be printed (3)");
+    EXPECT_THROW(
+            {
+                EXPECT_EQ(std::uncaught_exceptions(), 0);
+                auto printed = unwind_msg("this SHOULD be printed (2/2)");
+                { auto not_printed_4 = unwind_msg("this should NOT be printed (4)"); }
+                MyObj my_obj;
+                throw E("just testing");
+            }, E);
+}
+
+//-----------------------------------------------------------------------------
+
+GTEST_MAIN_RUN_ALL_TESTS()
diff --git a/vespalib/src/vespa/vespalib/util/CMakeLists.txt b/vespalib/src/vespa/vespalib/util/CMakeLists.txt
index 080b7715646..17fc14d0e9e 100644
--- a/vespalib/src/vespa/vespalib/util/CMakeLists.txt
+++ b/vespalib/src/vespa/vespalib/util/CMakeLists.txt
@@ -63,6 +63,7 @@ vespa_add_library(vespalib_vespalib_util OBJECT
     threadstackexecutor.cpp
     threadstackexecutorbase.cpp
     time.cpp
+    unwind_message.cpp
     valgrind.cpp
     zstdcompressor.cpp
     DEPENDS
diff --git a/vespalib/src/vespa/vespalib/util/unwind_message.cpp b/vespalib/src/vespa/vespalib/util/unwind_message.cpp
new file mode 100644
index 00000000000..8e96aa2110d
--- /dev/null
+++ b/vespalib/src/vespa/vespalib/util/unwind_message.cpp
@@ -0,0 +1,37 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "unwind_message.h"
+#include "stringfmt.h"
+#include <exception>
+
+namespace vespalib {
+
+UnwindMessage::UnwindMessage(const vespalib::string &msg)
+    : _num_active(std::uncaught_exceptions()),
+      _message(msg)
+{
+}
+
+UnwindMessage::UnwindMessage(UnwindMessage &&rhs)
+    : _num_active(std::uncaught_exceptions()),
+      _message(rhs._message)
+{
+    rhs._message.clear();
+}
+
+UnwindMessage::~UnwindMessage() {
+    if ((std::uncaught_exceptions() != _num_active) && !_message.empty()) {
+        fprintf(stderr, "%s\n", _message.c_str());
+    }
+}
+
+UnwindMessage unwind_msg(const char *fmt, ...)
+{
+    va_list ap;
+    va_start(ap, fmt);
+    vespalib::string msg = make_string_va(fmt, ap);
+    va_end(ap);
+    return {msg};
+}
+
+} // namespace
diff --git a/vespalib/src/vespa/vespalib/util/unwind_message.h b/vespalib/src/vespa/vespalib/util/unwind_message.h
new file mode 100644
index 00000000000..5133e92742d
--- /dev/null
+++ b/vespalib/src/vespa/vespalib/util/unwind_message.h
@@ -0,0 +1,33 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <vespa/vespalib/stllike/string.h>
+
+namespace vespalib {
+
+/**
+ * This class contains a message that will be printed to stderr if the
+ * object is destructed due to stack unwinding caused by an exception.
+ **/
+class UnwindMessage {
+private:
+    int _num_active;
+    vespalib::string _message;
+public:
+    UnwindMessage(const vespalib::string &msg);
+    UnwindMessage(UnwindMessage &&rhs);
+    UnwindMessage(const UnwindMessage &) = delete;
+    UnwindMessage &operator=(const UnwindMessage &) = delete;
+    UnwindMessage &operator=(UnwindMessage &&) = delete;
+    ~UnwindMessage();
+};
+
+extern UnwindMessage unwind_msg(const char *fmt, ...)
+#ifdef __GNUC__
+        // Add printf format checks with gcc
+        __attribute__ ((format (printf,1,2)))
+#endif
+    ;
+
+} // namespace