From 0091c4e12b3e25ecdf9c0da091e32739d7907d10 Mon Sep 17 00:00:00 2001
From: Max Kellermann <mk@cm4all.com>
Date: Mon, 1 Mar 2021 23:01:37 +0100
Subject: [PATCH] util/Exception: add FindNested()
---
src/util/Exception.hxx | 21 +++++++++++
test/util/TestException.cxx | 69 +++++++++++++++++++++++++++++++++++++
2 files changed, 90 insertions(+)
diff --git a/src/util/Exception.hxx b/src/util/Exception.hxx
index 390f5763f..3f131a260 100644
--- a/src/util/Exception.hxx
+++ b/src/util/Exception.hxx
@@ -83,6 +83,27 @@ NestException(std::exception_ptr ep, T &&t) noexcept
}
}
+/**
+ * Find an instance of #T in the nested exception chain, and return a
+ * pointer. Returns nullptr if no such instance was found.
+ */
+template<typename T>
+[[gnu::pure]]
+inline const T *
+FindNested(std::exception_ptr ep) noexcept
+{
+ try {
+ std::rethrow_exception(ep);
+ } catch (const T &t) {
+ return &t;
+ } catch (const std::nested_exception &ne) {
+ return FindNested<T>(ne.nested_ptr());
+ } catch (...) {
+ }
+
+ return nullptr;
+}
+
/**
* Find an instance of #T in the nested exception chain, and rethrow
* it. Does nothing if no such instance was found.
diff --git a/test/util/TestException.cxx b/test/util/TestException.cxx
index be4e557e5..947b86f91 100644
--- a/test/util/TestException.cxx
+++ b/test/util/TestException.cxx
@@ -50,6 +50,75 @@ TEST(ExceptionTest, DerivedError)
ASSERT_EQ(GetFullMessage(std::make_exception_ptr(DerivedError("Foo"))), "Foo");
}
+TEST(ExceptionTest, FindNestedDirect)
+{
+ struct Foo {};
+ struct Bar {};
+ struct Derived : Foo {};
+
+ try {
+ throw Foo{};
+ } catch (...) {
+ EXPECT_NE(FindNested<Foo>(std::current_exception()),
+ nullptr);
+ }
+
+ try {
+ throw Bar{};
+ } catch (...) {
+ EXPECT_EQ(FindNested<Foo>(std::current_exception()),
+ nullptr);
+ }
+
+ try {
+ throw Derived{};
+ } catch (...) {
+ EXPECT_NE(FindNested<Foo>(std::current_exception()),
+ nullptr);
+ }
+}
+
+TEST(ExceptionTest, FindNestedIndirect)
+{
+ struct Foo {};
+ struct Bar {};
+ struct Derived : Foo {};
+ struct Outer {};
+
+ try {
+ throw Foo{};
+ } catch (...) {
+ try {
+ std::throw_with_nested(Outer{});
+ } catch (...) {
+ EXPECT_NE(FindNested<Foo>(std::current_exception()),
+ nullptr);
+ }
+ }
+
+ try {
+ throw Bar{};
+ } catch (...) {
+ try {
+ std::throw_with_nested(Outer{});
+ } catch (...) {
+ EXPECT_EQ(FindNested<Foo>(std::current_exception()),
+ nullptr);
+ }
+ }
+
+ try {
+ throw Derived{};
+ } catch (...) {
+ try {
+ std::throw_with_nested(Outer{});
+ } catch (...) {
+ EXPECT_NE(FindNested<Foo>(std::current_exception()),
+ nullptr);
+ }
+ }
+}
+
template<typename T>
static bool
CheckFindRetrowNested(std::exception_ptr e) noexcept