From e308552eccbab74069c30bc2234cd26e5e5e1f9f Mon Sep 17 00:00:00 2001
From: Julian Brost <julian.brost@icinga.com>
Date: Thu, 6 Mar 2025 11:46:48 +0100
Subject: [PATCH] Add test that std::vector<icinga::String> uses move overloads

---
 test/CMakeLists.txt  |  1 +
 test/base-string.cpp | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index a255178da..6ceb48683 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -165,6 +165,7 @@ add_boost_test(base
     base_string/replace
     base_string/index
     base_string/find
+    base_string/vector_move
     base_timer/construct
     base_timer/interval
     base_timer/invoke
diff --git a/test/base-string.cpp b/test/base-string.cpp
index 835b1a643..5b28c5481 100644
--- a/test/base-string.cpp
+++ b/test/base-string.cpp
@@ -1,6 +1,7 @@
 /* Icinga 2 | (c) 2012 Icinga GmbH | GPLv2+ */
 
 #include "base/string.hpp"
+#include <vector>
 #include <BoostTestTargetConfig.h>
 
 using namespace icinga;
@@ -101,4 +102,28 @@ BOOST_AUTO_TEST_CASE(find)
 	BOOST_CHECK(s.FindFirstOf("xl") == 2);
 }
 
+// Check that if a std::vector<icinga::String> is grown beyond its capacity (i.e. it has to reallocate the memory),
+// it uses the move constructor of icinga::String (i.e. the underlying string storage stays the same).
+BOOST_AUTO_TEST_CASE(vector_move)
+{
+	std::vector<String> vec {
+		// std::string (which is internally used by icinga::String) has an optimization that small strings can be
+		// allocated inside it instead of in a separate heap allocation. In that case, the small string would still be
+		// copied even by the move constructor. Using sizeof() ensures that the string is long enough so that it must
+		// be allocated separately and can be used to test for the desired move to happen.
+		std::string(sizeof(String) + 1, 'A'),
+	};
+
+	void *oldAddr = vec[0].GetData().data();
+	// Sanity check that the data buffer is actually allocated outside the icinga::String instance.
+	BOOST_CHECK(!(&vec[0] <= oldAddr && oldAddr < &vec[1]));
+
+	// Force the vector to grow.
+	vec.reserve(vec.capacity() + 1);
+
+	// If the string was moved, the location of its underlying data buffer should not have changed.
+	void *newAddr = vec[0].GetData().data();
+	BOOST_CHECK_EQUAL(oldAddr, newAddr);
+}
+
 BOOST_AUTO_TEST_SUITE_END()